<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">JMP</journal-id><journal-title-group><journal-title>Journal of Modern Physics</journal-title></journal-title-group><issn pub-type="epub">2153-1196</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/jmp.2014.58082</article-id><article-id pub-id-type="publisher-id">JMP-46476</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>PHYSICS &amp; MATHEMATICS</subject></subj-group></article-categories><title-group><article-title>Some New Features of Photon Statistics in a Fully Quantized Parametric Amplification Process</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Joseph</surname><given-names>Akeyo Omolo</given-names></name><xref ref-type="aff" rid="aff1"><sub>1</sub></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Department of Physics, Maseno University, Maseno, Kenya</addr-line></aff><author-notes><corresp id="cor1">* E-mail:<email>ojakeyo04@yahoo.co.uk</email></corresp></author-notes><pub-date pub-type="epub"><day>21</day><month>05</month><year>2014</year></pub-date><volume>05</volume><issue>08</issue><fpage>706</fpage><lpage>723</lpage><history><date date-type="received"><day>31</day>	<month>January</month>	<year>2014</year></date><date date-type="rev-recd"><day>21</day>	<month>February</month>	<year>2014</year>	</date><date date-type="accepted"><day>9</day>	<month>March</month>	<year>2014</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
	An exact
quantum treatment reveals that signal and idler photon number operators are not
well-behaved dynamical operators for studying photon statistics in parametric
amplification/down-conversion processes. Contrary to expectations, the mean
signal-idler photon number difference <disp-formula id="scirp.46476-formula1628"><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/Edit_47467a09-bdf8-4220-bff6-1e125c04b088.bmp"/></disp-formula> varies with time,
while the corresponding signal-idler photon number cross-correlation function <!--[if gte vml 1]><v:shape id="_x0000_i1026" type="#_x0000_t75" style="width:49.5pt;height:19.5pt;" o:ole="">
 <v:imagedata src="file:///C:\Users\scirp\AppData\Local\Temp\msohtmlclip1\01\clip_image003.wmz" o:title="" />
</v:shape><![endif]--><!--[if !vml]--><disp-formula id="scirp.46476-formula1629"><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/Edit_56cdf415-42d6-442e-8f47-c784274dd7f5.bmp"/></disp-formula><!--[endif]--><!--[if gte mso 9]><xml>
 <o:oleobject type="Embed" progid="Equation.DSMT4" shapeid="_x0000_i1026" drawaspect="Content" objectid="_1462950464">
 </o:oleobject>
</xml><![endif]--> is complex and
experiences an interference phenomenon driven by the interaction parameters.
The intensity operators and related polarization operators of the polarized
signal-idler photon pair in positive and negative helicity states are
identified as the appropriate operators specifying a conservation law and the
dynamical symmetry group (SU(1, 1))
of the parametric amplification process. The conservation of the mean positive
and negative helicity photon intensity difference and the purely real
positive-negative helicity intensity cross-correlation function correctly
account for the simultaneous production of polarized signal and idler photons
in positive and negative helicity states. 
</p></abstract><kwd-group><kwd>Quantized Parametric Amplification</kwd><kwd> Jaynes-Cummings Interaction</kwd><kwd> Fluctuation State Vectors</kwd><kwd> Fractional Revivals</kwd><kwd> Interference</kwd><kwd> Positive-Negative Helicity Intensity/Polarization Operators</kwd><kwd> &lt;i&gt;SU&lt;/i&gt;(1</kwd><kwd> 1) Symmetry Group</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>The fully quantized parametric amplification process treated in this paper consists of a pump photon of angular frequency ω, annihilation operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8652605a-38ee-4b8a-87af-7c0aeaabc798.png" xlink:type="simple"/></inline-formula> and creation operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\605252e2-dba6-4c40-a57b-245d0b42277f.png" xlink:type="simple"/></inline-formula> interacting with a non-linear crystal to gener- ate two photons, the signal and idler, of angular frequencies<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e5832e82-23ff-40f5-a994-5b5315de5c21.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\da7ccd27-d7df-4581-916a-fc2032077902.png" xlink:type="simple"/></inline-formula>, annihilation operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7c5afa7d-a0d3-4472-a21b-339161519f64.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c99cba8e-8ffc-4dba-8d75-691343ba4c82.png" xlink:type="simple"/></inline-formula>and crea- tion operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bca92409-d3b8-439c-b398-b85436eb8e88.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c2fdcb96-5911-47b7-bbcd-4cdf0e188a47.png" xlink:type="simple"/></inline-formula>, respectively. The model Hamiltonian for this process is obtained in the trilinear form [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref2">2</xref>]</p><disp-formula id="scirp.46476-formula1490"><label>(1)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\27ed354d-8901-48ab-a1ea-3ca42ce5775a.png"/></disp-formula><p>where g is a constant coupling parameter.</p><p>Transformation to the interaction frame through application of a transformation operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3681c5a8-ef7e-491f-ba17-6b6d77127ab9.png" xlink:type="simple"/></inline-formula> according to a general transformation law</p><disp-formula id="scirp.46476-formula1491"><label>(2a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a73e042a-eb8e-4937-b7ca-bb8f43dc0ee7.png"/></disp-formula><p>where the transformation operator takes the form</p><disp-formula id="scirp.46476-formula1492"><label>(2b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\82b770d8-b1fb-45b0-961e-58bf2fd870de.png"/></disp-formula><p>puts the Hamiltonian H from Equation (1) into an interaction form</p><disp-formula id="scirp.46476-formula1493"><label>(2c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e421631c-de12-4a22-818f-57b5fb531b7c.png"/></disp-formula><p>which specifically describes the interaction of signal (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a2b024d3-5408-4758-96a6-2af05a3d44ec.png" xlink:type="simple"/></inline-formula>-mode) and idler (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f9f4a9af-6355-4bd5-ad8a-ceaf643d12b1.png" xlink:type="simple"/></inline-formula>-mode) photons coupled by a sin- gle quantized pump photon (a-mode).</p><p>The time evolution equations governing the dynamics of signal and idler photons are obtained through Hei- senberg’s equations for the annihilation and creation operator pair (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ff61bb92-fdc7-42b9-9439-5d86d754772f.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6e4610cf-01ee-4ae7-aad5-e097abe428e4.png" xlink:type="simple"/></inline-formula>) in the form</p><disp-formula id="scirp.46476-formula1494"><label>(3a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\19c70259-2266-4f77-bde9-4d3d90bbcf2c.png"/></disp-formula><p>which on substituting <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\efdf6156-dfaf-4dcd-a9f5-cb154a3a46d0.png" xlink:type="simple"/></inline-formula> from Equation (2c) become</p><disp-formula id="scirp.46476-formula1495"><label>(3b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4025a031-6d97-443a-8ab3-485845ab4055.png"/></disp-formula><disp-formula id="scirp.46476-formula1496"><label>(3c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\57d95271-79f7-4ae6-9d85-70f91a4a12d2.png"/></disp-formula><p>The general procedure for obtaining exact analytical solutions to these equations has been developed by the present author in a recent paper on fully quantized parametric oscillation/frequency-conversion process [<xref ref-type="bibr" rid="scirp.46476-ref3">3</xref>] . A summary of the procedure is presented in the next section to obtain exact analytical solutions for a fully quan- tized parametric amplification/down-conversion process.</p></sec><sec id="s2"><title>2. The Matrix Method: Jaynes-Cummings Interaction</title><p>The coupled time evolution Equations (3b), (3c) are expressed in an appropriate matrix form by introducing a two-component signal-idler photon annihilation-creation operator column matrix <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\946436d6-8822-42e6-88bd-c50b7da0e8a6.png" xlink:type="simple"/></inline-formula> defined by</p><disp-formula id="scirp.46476-formula1497"><label>(4a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\27510dd4-1fea-4172-964b-479e4a6a2869.png"/></disp-formula><p>to obtain</p><disp-formula id="scirp.46476-formula1498"><label>(4b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c05611d9-8f30-4f93-b48a-4e03787f3c84.png"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\22a1a20f-b552-4ac2-9f48-0faa7fd03f31.png" xlink:type="simple"/></inline-formula> is a <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\24e8a0ba-0553-4ba4-9f44-1f999c9a46a6.png" xlink:type="simple"/></inline-formula> Hamiltonian matrix obtained as</p><disp-formula id="scirp.46476-formula1499"><label>(4c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\485c47d4-92cb-47e5-9580-edf409e92b21.png"/></disp-formula><p>Introducing the <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0f82fa60-d2f7-4296-83f2-2c3ef84d624f.png" xlink:type="simple"/></inline-formula> identity and the usual Pauli spin operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\700d4947-7cca-4582-8eac-511299633f5f.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8a240580-0cac-4784-8b75-f8e5b8fabcc0.png" xlink:type="simple"/></inline-formula>, giving</p><disp-formula id="scirp.46476-formula1500"><label>(5)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\16caa520-c4a0-4eae-9f59-b531ec4fc6dd.png"/></disp-formula><p>the Hamiltonian matrix in Equation (4c) is expressed in the form</p><disp-formula id="scirp.46476-formula1501"><label>(6a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\2756b838-5139-4345-8272-81c734bc5bac.png"/></disp-formula><p>where the frequency difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4bc66f87-064d-4c52-ace8-4e088c6457ca.png" xlink:type="simple"/></inline-formula> and sum <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7a964ddb-1b40-452b-8033-00b649f4a5b9.png" xlink:type="simple"/></inline-formula> are defined by</p><disp-formula id="scirp.46476-formula1502"><label>(6b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bb2e268b-4275-48c0-be08-4bf1af95e8a0.png"/></disp-formula><p>An important point to note here is that, except for the factor <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\78090723-3e1a-48f2-ab1d-6698ed41d054.png" xlink:type="simple"/></inline-formula> in the interaction term specifying the parametric interaction mechanism, the Hamiltonian H in Equation (6a) takes the form of a Jaynes-Cummings interaction Hamiltonian [<xref ref-type="bibr" rid="scirp.46476-ref4">4</xref>] -[<xref ref-type="bibr" rid="scirp.46476-ref10">10</xref>] for a 2-level atom interacting with a quantized single-mode electromagnetic field. Since the interaction term <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5b6810b4-898c-48b9-a693-21d4b81c24ad.png" xlink:type="simple"/></inline-formula> of <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5a9f9e44-4e64-4737-8609-fa6b89ba881a.png" xlink:type="simple"/></inline-formula> in Equation (6a) is anti-Hermitian according to</p><disp-formula id="scirp.46476-formula1503"><label>(6c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\54e6b357-a4d4-45d0-93cf-4a80374b7c97.png"/></disp-formula><p>it may appropriately be referred to as an anti-Jaynes-Cummings Hamiltonian.</p><p>In this respect, the Hamiltonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9f3b283e-dc7a-4ed4-a6af-db14d4397194.png" xlink:type="simple"/></inline-formula> in Equation (6a) is non-Hermitian, yet it generates the internal dynamics of a non-dissipative parametric amplification process governed by the original Hermitian Hamiltonian H in Eq- uation (1).</p><sec id="s2_1"><title>2.1. Signal-Idler Photon Polarization Operator Vector</title><p>To gain complete understanding of the 2-level Jaynes-Cummings mode of interaction in the fully quantized pa- rametric amplification process, consider that according to Equation (4b), the Jaynes-Cummings interaction Ha- miltonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1ff153c8-eeb9-48b8-9863-f656e598a27e.png" xlink:type="simple"/></inline-formula> generates of the dynamics vector the signal-idler photon system by operating on the two-com- ponent operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9b86b085-672c-432f-81f3-37b12ba6a011.png" xlink:type="simple"/></inline-formula> defined in Equation (4a), which is now expressed in the appropriate form</p><disp-formula id="scirp.46476-formula1504"><label>(7a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\99555cd5-fbf3-49b1-8557-ff645db05a4d.png"/></disp-formula><p>after introducing the 2-dimensional Hilbert space basis vectors <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8e188dc9-0da8-4ed7-8771-370cc7bd2a61.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bfaf1a81-52b9-4085-b7d2-ac3ee814b0c8.png" xlink:type="simple"/></inline-formula> defined as usual by</p><disp-formula id="scirp.46476-formula1505"><label>(7b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6fb5d091-e608-4032-bcba-080f54632d99.png"/></disp-formula><p>It is clear that <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\16868156-60f7-4e27-a1b8-da82ffd1df72.png" xlink:type="simple"/></inline-formula> takes exactly the form of a two-level atomic state vector as defined within the standard Jaynes-Cummings model in quantum optics [<xref ref-type="bibr" rid="scirp.46476-ref4">4</xref>] -[<xref ref-type="bibr" rid="scirp.46476-ref10">10</xref>] and in general quantum mechanics. In standard photon dy- namics, the basis vectors <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c34d2747-b048-4db2-87ed-1ab8f50ca538.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\84a58eeb-bbdc-43a4-9767-a78dd8ceef08.png" xlink:type="simple"/></inline-formula> are interpreted as the basic circular polarization state vectors. In partic- ular, using the Pauli matrix <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7e478d53-103e-4d27-b5d9-eba6ba965d30.png" xlink:type="simple"/></inline-formula> defined by</p><disp-formula id="scirp.46476-formula1506"><label>(7c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7c19f6c7-7bd6-4351-ba6f-a45d13ecd91d.png"/></disp-formula><p>gives</p><disp-formula id="scirp.46476-formula1507"><label>(7d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\60c204b6-b5bc-46a2-abc0-32e1bb1d5c87.png"/></disp-formula><p>which leads to the standard interpretation that <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\17b84f6a-c4b8-41b3-84ca-6f26e03e7c8c.png" xlink:type="simple"/></inline-formula> is a positive helicity state vector, while <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\18df2be0-c19c-487b-a595-ea68df20f50d.png" xlink:type="simple"/></inline-formula> is a negative helicity state vector for circularly polarized photons [<xref ref-type="bibr" rid="scirp.46476-ref11">11</xref>] .</p><p>The two-component vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\42a86048-39f1-4063-a7a5-ada895859a49.png" xlink:type="simple"/></inline-formula> is then specifically interpreted as a polarization operator vector for the coupled circularly polarized signal-idler photon pair. The component annihilation and creation operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\490e9e56-d918-4faa-a81b-c1a6a8a3bddf.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cff4176e-63da-473e-9940-4cb486560b99.png" xlink:type="simple"/></inline-formula> are interpreted as photon intensity operator amplitudes for signal and idler photons in positive and neg- ative helicity states <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\46633dca-3fef-4aaf-aaa3-3b5c21c389aa.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a3eee333-e45e-4da9-bde7-06a4ec32fb47.png" xlink:type="simple"/></inline-formula>, respectively.</p><p>Using <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fa5d27d2-7a56-48e7-960e-d803abbb6d90.png" xlink:type="simple"/></inline-formula> from Equation (7a) and its Hermitian conjugate <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\431f2274-4568-4138-b50a-e7a7907027f1.png" xlink:type="simple"/></inline-formula> obtained as</p><disp-formula id="scirp.46476-formula1508"><label>(7e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\002c46a0-40fb-4285-b6ec-2ba5275cc485.png"/></disp-formula><p>the total signal-idler photon intensity operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\62534e4f-2466-42ed-905c-1790befc4285.png" xlink:type="simple"/></inline-formula> follows from the inner product according to</p><disp-formula id="scirp.46476-formula1509"><label>(7f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\80063ed5-49be-4da1-8407-24ce1b9a7dca.png"/></disp-formula><p>after introducing positive and negative helicity polarized signal-idler photon intensity operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3c64bd89-a0a1-4302-96d4-12b06789bec0.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3327d71d-809e-4d6a-bb27-53a45f98002b.png" xlink:type="simple"/></inline-formula>, re- spectively obtained as</p><disp-formula id="scirp.46476-formula1510"><label>(7g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c7d27758-91c0-4d63-b41c-1e800d3f1f18.png"/></disp-formula><p>It follows from Equations (4b), (6a) and (7a) that the underlying dynamics in a fully quantized parametric amplification process is a two-state dynamics characterized by the time evolution of circular polarization state vectors of the coupled signal-idler photon pair generated by a Jaynes-Cummings mode of interaction. This leads to the general interpretation that the coupled signal-idler photon pair constitutes a composite circularly polarized two-state system specified by the positive and negative helicity states interacting with a single-mode quantized pump field equivalent to an (anti)-Jaynes-Cummings model for a single two-level atom. A comprehensive pres- entation of photon polarization state dynamics in linear and nonlinear quantum optics is currently under prepara- tion in a more elaborate paper by the present author.</p></sec><sec id="s2_2"><title>2.2. General Solution</title><p>A complete picture of the Jaynes-Cummings mode of interaction is obtained by transforming Equation (4b) back to the original frame by applying the inverse operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7bdfd03d-4037-4a60-84ed-0e2fbb6577ef.png" xlink:type="simple"/></inline-formula> from Equation (2b) according to</p><disp-formula id="scirp.46476-formula1511"><label>(8a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4d8d0dc0-bee4-4423-b95e-fa4e6569e101.png"/></disp-formula><p>which is used in Equation (4b) to obtain the effective time evolution equation in the original frame in the form</p><disp-formula id="scirp.46476-formula1512"><label>(8b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\280c1013-e5bf-412f-8395-db205a48026b.png"/></disp-formula><p>where the Hamiltonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\40e819d8-5654-4666-ab0f-08feb89a5dcc.png" xlink:type="simple"/></inline-formula> follows from the transformation in the form</p><disp-formula id="scirp.46476-formula1513"><label>(8c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\18246068-2a3d-47dc-b277-d4f2f0a12ea0.png"/></disp-formula><p>This essentially reverses the general transformation law in Equation (2a) as expected. Substituting <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\40657830-f8db-451d-b2f5-5d1e47eb7eaf.png" xlink:type="simple"/></inline-formula> from Equation (6a) into Equation (8c) and applying standard algebraic relations gives the final form</p><disp-formula id="scirp.46476-formula1514"><label>(8d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\53890582-84f5-4e64-bc06-46eb6998f3ec.png"/></disp-formula><p>The obvious interpretation is that <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c894997f-5eed-4c42-89ec-ff3dc799d39a.png" xlink:type="simple"/></inline-formula> in Equation (8d) is the full (anti)-Jaynes-Cummings Hamiltonian which generates the dynamics of a fully quantized parametric amplification process through its action on the signal-idler photon polarization operator vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bca5a3fb-d40d-489f-bf0f-f319b40e73b2.png" xlink:type="simple"/></inline-formula> according to Equation (8b). The anti-Hermitian property of its interaction term <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\75e02b3e-e317-4af4-b11c-bf7890010d53.png" xlink:type="simple"/></inline-formula> is responsible for the characteristic features of the amplification process. As observed earlier, the non-Hermitian nature of <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a2e306f5-bae7-4a36-a870-5135e683e649.png" xlink:type="simple"/></inline-formula> is not in any way associated with dissipation, since the (anti)-Jaynes-Cummings mode of interaction only characterizes the general dynamics generated by the original continuous variable operator Hermitian Hamiltonian H in Equation (1).</p><p>The time evolution Equation (8b) can now be solved exactly by applying the usual procedure for solving the Jaynes-Cummings problem in quantum optics [<xref ref-type="bibr" rid="scirp.46476-ref9">9</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref10">10</xref>] . Adding and subtracting <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8241a428-e8aa-4f7f-8463-9a191cb22dea.png" xlink:type="simple"/></inline-formula> in Equation (8e) and in- troducing frequency detuning δ defined by</p><disp-formula id="scirp.46476-formula1515"><label>(9a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d623efe6-c13c-4251-9bae-d9ec14f30ad0.png"/></disp-formula><p>puts <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\666e8e00-a63f-4da2-8d7d-24f4d66718df.png" xlink:type="simple"/></inline-formula> in the form</p><disp-formula id="scirp.46476-formula1516"><label>(9b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8191c286-4756-4a5d-a74f-93dbd82d494e.png"/></disp-formula><p>where the operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7d608724-9247-416a-bb23-e5ebd32f923b.png" xlink:type="simple"/></inline-formula> and interaction Hamiltonian H are defined by</p><disp-formula id="scirp.46476-formula1517"><label>(9c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f05ada91-3de3-4ae5-ad2b-aebc194b382b.png"/></disp-formula><p>Using standard algebraic relations for<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a882ea68-b908-4174-b60b-3a7ddcdcd4b3.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\449aa93d-2f28-4a34-86d0-fc71d87056cd.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8f4005ab-84ef-4ceb-bfef-9efa0121cde1.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ab790fbe-76d0-49f4-9090-a7d8981a27c7.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a4c748ec-9fec-4091-b85e-2c093c8a62ff.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b8e7062a-90f0-4477-adbe-e42e7e52d98c.png" xlink:type="simple"/></inline-formula>easily gives</p><disp-formula id="scirp.46476-formula1518"><label>(9d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\77b2b05f-7886-42b9-8bf8-ceb116b0968b.png"/></disp-formula><p>Since both components <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1a969892-68a9-4566-add7-efc47c2e1300.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9103ef82-1956-4c0f-b4d8-4f77f0d97bdd.png" xlink:type="simple"/></inline-formula> commute with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ac88eb3a-cfef-4ea2-86ea-5d0864934a4c.png" xlink:type="simple"/></inline-formula>, they are constants of the motion. The Hamil- tonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a7d2372b-71f0-44c0-975e-cfa26fd79dc0.png" xlink:type="simple"/></inline-formula> is thus time-independent, leading to a solution of the time evolution Equation (8b) through simple integration giving</p><disp-formula id="scirp.46476-formula1519"><label>(10a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\2e970d6d-0d48-4cad-b3fd-bd1a68e96c6a.png"/></disp-formula><p>where the initial polarization operator vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ee952c85-1de2-4a56-b84e-08fefecac3a8.png" xlink:type="simple"/></inline-formula> takes the form in Equation (7a). The general time evo- lution operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7f76f5dd-be46-49c1-a2c9-a822b246c5ab.png" xlink:type="simple"/></inline-formula> governing the dynamics under <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ecfe793e-5e51-4419-b527-089ccb4165d2.png" xlink:type="simple"/></inline-formula> has been obtained as</p><disp-formula id="scirp.46476-formula1520"><label>(10b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5cc8a5b3-128b-4fb7-bc5a-ecd1772a4417.png"/></disp-formula><p>after applying the commutation of <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6c7b41fa-cc65-4193-95d1-c4dafbf5a48c.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4f2b5576-5c27-44c1-9279-2f69525f1952.png" xlink:type="simple"/></inline-formula> as in Equation (9d) and using</p><disp-formula id="scirp.46476-formula1521"><label>(10c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\47bb44fe-c675-4ca0-a9b9-8ebcb189b69d.png"/></disp-formula><disp-formula id="scirp.46476-formula1522"><label>(10d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\152873af-2994-47c1-83d4-47260f2ed2cf.png"/></disp-formula><sec id="s2_2_1"><title>2.2.1. Evaluating <img src="htmlimages\16-7501380x\fcb321aa-f9b3-40ec-98fc-327f8b51c3be.png" width="82.5" height="42.5" /></title><p>Substituting <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ee84c38c-558a-4c63-abaa-039beabcd1a1.png" xlink:type="simple"/></inline-formula> from Equation (10d) into Equation (10b) and using <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\661f04a3-2f1f-46b3-9a6d-5931b28f4f91.png" xlink:type="simple"/></inline-formula> from Equation (9c) gives <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ec457852-03dd-4d94-901d-1d52a77d0dc4.png" xlink:type="simple"/></inline-formula> in the form</p><disp-formula id="scirp.46476-formula1523"><label>(11a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5798ec46-ac68-418e-94c8-49a0c34aedd0.png"/></disp-formula><p>after considering that the identity <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\976bbe19-4f49-47b5-8681-72f565738c16.png" xlink:type="simple"/></inline-formula> commutes with the rest of the operators to effect a factorization as appropriate. Expanding the exponential operator in Equation (11a) and carrying out straightforward algebraic manipulation with details presented in [<xref ref-type="bibr" rid="scirp.46476-ref3">3</xref>] yields the final form</p><disp-formula id="scirp.46476-formula1524"><label>(11b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\94e74ab7-63e5-4c9d-a0ef-41d231a25b07.png"/></disp-formula><p>after introducing the time evolving pump photon interaction operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\78d7b8e3-2fa7-4f5d-99fb-b9628c4840bc.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\52e18c47-47a0-46ec-be52-04bd47ac6166.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\80f86358-ae38-4459-bc77-e235ad6a0619.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\64c0ff31-c967-4de2-9e6d-44e376c4fa61.png" xlink:type="simple"/></inline-formula>defined by</p><disp-formula id="scirp.46476-formula1525"><label>(12a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\61792b5a-9245-4e99-a825-8c1e3b7a036a.png"/></disp-formula><disp-formula id="scirp.46476-formula1526"><label>(12b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5dc0c516-30f6-4bb9-88e8-ae6fc474018b.png"/></disp-formula><disp-formula id="scirp.46476-formula1527"><label>(12c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c6ddcfcb-d3c8-4fad-a6af-edacb434ffc7.png"/></disp-formula><disp-formula id="scirp.46476-formula1528"><label>(12d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d8fa97be-0174-4c3a-8495-b6405361b054.png"/></disp-formula><p>with Hermitian conjugates easily obtained as</p><disp-formula id="scirp.46476-formula1529"><label>(12e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f9cfebcf-a440-4170-ab7b-f190aee1ef06.png"/></disp-formula><disp-formula id="scirp.46476-formula1530"><label>(12f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\aff9a87f-b179-4a42-8530-298182e828d1.png"/></disp-formula><disp-formula id="scirp.46476-formula1531"><label>(12g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fab22d93-5791-4c48-9838-297ba160fef0.png"/></disp-formula><disp-formula id="scirp.46476-formula1532"><label>(12h)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\38fbcb97-d7d8-4444-a8b4-ffe3766e183d.png"/></disp-formula></sec><sec id="s2_2_2"><title>2.2.2. Evaluating <img src="htmlimages\16-7501380x\14be538e-5ba3-4020-a26d-63339b2581ad.png" width="60" height="45" /></title><p>Substituting <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e0f0c08d-b9a3-4d88-9b58-6a5d88c68f1d.png" xlink:type="simple"/></inline-formula> from Equation (11b) into Equation (10a), using the initial <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d593c309-117b-4885-91a3-886766d22893.png" xlink:type="simple"/></inline-formula> from Equa- tion (7a), together with T(t) from Equation (10c) and applying</p><disp-formula id="scirp.46476-formula1533"><label>(13a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\66f9846e-a8f8-44f7-91ff-1888b200e62c.png"/></disp-formula><disp-formula id="scirp.46476-formula1534"><label>(13b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5abd9547-4d88-48c1-9587-6bc768035c4b.png"/></disp-formula><p>then reorganizing the result gives the final form</p><disp-formula id="scirp.46476-formula1535"><label>(14a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\59720e1c-a93a-4de6-b52e-2f983077bb34.png"/></disp-formula><p>where the general time evolving signal photon annihilation operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9895c630-adfb-436e-8c07-d531e5244856.png" xlink:type="simple"/></inline-formula> and idler photon creation operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4fec09ec-8174-4c81-9d20-47cda8ab0e7b.png" xlink:type="simple"/></inline-formula> have been obtained in the form</p><disp-formula id="scirp.46476-formula1536"><label>(14b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1567cb63-bbf4-4f09-9e20-d93c4e933c1f.png"/></disp-formula><disp-formula id="scirp.46476-formula1537"><label>(14c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1807654a-b1c7-4ae1-b8d9-c1275a940d27.png"/></disp-formula><p>These are the desired exact analytical solutions determined within the Heisenberg picture, where they can be used in the calculation of mean values, fluctuations and cross-correlation functions of various physical quantities which characterize the dynamics of a fully quantized parametric amplification process generated by the trilinear Hamiltonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\89dc6744-73bd-4813-a636-c5ea38c9c2ed.png" xlink:type="simple"/></inline-formula> in Equation (1).</p></sec></sec><sec id="s2_3"><title>2.3. Pump Photon Operator Action on Fock State <img src="htmlimages\16-7501380x\f1133ce7-8cf8-40fa-89af-be29ec03f5cc.png" width="40" height="45" /></title><p>The pump photon operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b4a2ec35-21d5-4334-aeab-407ef8c76c2a.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\704e972b-f5bf-446e-a4b5-d427032752fd.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\17e65266-45ef-4d6e-b0ee-29d93f75ad6a.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\034107cf-28b6-4cd8-9a1a-8a59643a5878.png" xlink:type="simple"/></inline-formula>, together with their Hermitian conjugates defined in the set of Equations (12a)-(12h) act on the pump photon Fock state vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\996d5540-e0cc-4564-873c-b78b2466ba97.png" xlink:type="simple"/></inline-formula> according to [<xref ref-type="bibr" rid="scirp.46476-ref3">3</xref>]</p><disp-formula id="scirp.46476-formula1538"><label>(15a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8dd77b7e-08d6-4de6-96ee-20cd12b713c9.png"/></disp-formula><disp-formula id="scirp.46476-formula1539"><label>(15b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\32792928-d863-4194-9071-d2caa864b5b0.png"/></disp-formula><disp-formula id="scirp.46476-formula1540"><label>(15c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cab8fe93-5e12-4ff3-9032-3e7fdb66424b.png"/></disp-formula><disp-formula id="scirp.46476-formula1541"><label>(15d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\11d8ceb5-346c-4bdd-8da6-5d885f38e53c.png"/></disp-formula><disp-formula id="scirp.46476-formula1542"><label>(15e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4b7b3b88-616c-46d6-90cd-6899e48dab58.png"/></disp-formula><p>which provide useful c-number variables<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\66abe087-717d-4d46-9d3d-31d829dc3184.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b0000422-aab6-4ead-8e26-672c9e64b234.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f53d0818-2229-4e77-b465-520e2c5218f9.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\74a6f81d-a3a0-4724-aba9-e4eab10f086f.png" xlink:type="simple"/></inline-formula>in explicit forms to describe features of the dy- namics. It is to be noted that<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\da40a04f-f6c8-46cf-9575-621980ebb002.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ceb3a43a-2c68-411a-ac1e-ec752c6c2a97.png" xlink:type="simple"/></inline-formula>generate eigenvalue equations, while <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\71689df3-33ad-43ee-96ca-f0247b65c164.png" xlink:type="simple"/></inline-formula> acts like an annihilation opera- tor and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\643bcc4e-b79a-49d8-92a5-67f4bd1f7583.png" xlink:type="simple"/></inline-formula> acts like a creation operator. Indeed, using Equations (15b) and (15d) shows that the operator prod- ucts <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c075ab9d-5447-4882-9a8e-b02ffd15f716.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\75e6f1bb-aac9-4731-9feb-77a47349e621.png" xlink:type="simple"/></inline-formula> act like photon number operators according to</p><disp-formula id="scirp.46476-formula1543"><label>(15f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b215f295-f238-421b-a561-38316459f3bd.png"/></disp-formula><p>where</p><disp-formula id="scirp.46476-formula1544"><label>(15g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\017f144a-a523-45e8-82c1-d705cc5c5d7b.png"/></disp-formula><p>show that <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\52b89742-c0c6-43a8-b0b5-17ce3c518b32.png" xlink:type="simple"/></inline-formula> is easily obtained by setting n → n + 1 in Equation (15b), while <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ebdc49ad-3bc4-4ca5-b426-02aa79a9a720.png" xlink:type="simple"/></inline-formula> is easily obtained by setting n → n − 1 in Equation (15d). These simple operations apply to the pump photon Fock state and indeed to vari- ous forms of the pump photon initial state vectors generally expressible as superpositions of Fock state vectors.</p></sec></sec><sec id="s3"><title>3. Fluctuation (Noise) State Vectors</title><p>State vectors which describe the fluctuations of various physical quantities (observables) are here referred to as fluctuation state vectors in the sense that their occupation numbers (or inner products) define the fluctuations. The interpretation of fluctuations as noise may also lead to a corresponding reference as noise state vectors. The fluctuation (noise) state vectors are generated through repeated application of annihilation (fundamental) or cre- ation (dual) operators on the appropriate initial state vectors. The action of the annihilation or creation operators causes de-excitation or excitation, which generally produce fluctuations or noise during measurements. In gen- eral, repeated applications of annihilation and creation operators in appropriate order are equivalent to opera- tions with corresponding observable operators formed as products of the annihilation and creation operators.</p><p>In this study, the initial state vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cbd37cc4-c9d6-4fe8-878f-8a64e0ab5a0f.png" xlink:type="simple"/></inline-formula> of the pump, signal and idler photons is taken as the Fock state vector defined using usual notation in the product form</p><disp-formula id="scirp.46476-formula1545"><label>(16a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\87f60220-d37c-4e1d-b9ea-e9c3f1d6bd3c.png"/></disp-formula><p>For an observable represented by an operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\95c88348-f184-40e4-afaa-97e459a35938.png" xlink:type="simple"/></inline-formula> at any time t ≥ 0, the Q-fluctuation state vector is ob- tained as</p><disp-formula id="scirp.46476-formula1546"><label>(16b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\06d86590-26ff-4660-92ba-70a101234fc5.png"/></disp-formula><p>The Q-mean value is obtained as</p><disp-formula id="scirp.46476-formula1547"><label>(16c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6ff74747-0f90-4b4b-95eb-53a30776276a.png"/></disp-formula><p>while the Q-second moment is obtained as the occupation number (or inner product) according to</p><disp-formula id="scirp.46476-formula1548"><label>(16d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\26f09051-2dc9-46d3-a7d0-ed2a6e46116a.png"/></disp-formula><p>The Q-fluctuation is obtained using equations (16c)-(16d) in the general form</p><disp-formula id="scirp.46476-formula1549"><label>(16e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\040073cf-6555-4577-85f7-7ec7e36f265d.png"/></disp-formula><p>For two observables represented by operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b31d059e-1596-4bcd-8fec-b82289c723a0.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\2e178380-8d8a-47f3-a13d-ccba92043e78.png" xlink:type="simple"/></inline-formula>, where j , k are suitable labels, which can be numbers or appropriate symbols, the cross-correlation functions are obtained according to</p><disp-formula id="scirp.46476-formula1550"><label>(16f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cb22c3fe-f8c1-47e9-8276-ccf53cc29acf.png"/></disp-formula><p>while the cross-correlation fluctuations defined by</p><disp-formula id="scirp.46476-formula1551"><label>(16g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ab087ac5-2b68-4538-81ff-79791da0a7d9.png"/></disp-formula><p>are obtained according to</p><disp-formula id="scirp.46476-formula1552"><label>(16h)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\69533523-99a2-4f7e-b19e-63388e6e3d1c.png"/></disp-formula><p>These results are general enough to apply to various operators and their Hermitian conjugates.</p></sec><sec id="s4"><title>4. Signal and Idler Photon Number Fluctuation State Vectors</title><p>This section investigates the suitability of the signal and idler photon number operators<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ace7ea30-a5ea-4580-b2b1-647dfbb1577f.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b6c8ff52-f89c-42a9-9f94-4adaeea4b2f8.png" xlink:type="simple"/></inline-formula>as dy- namical operators for studying photon statistics in a fully quantized parametric amplification process. In this re- spect, the observable operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ac9948af-0dee-488a-92e6-04e9b2d07903.png" xlink:type="simple"/></inline-formula> is the photon number. For signal and idler photons, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\581d8905-7512-4df3-a8d0-1edfac28e581.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cdec5fce-bd9c-4bc9-a310-3698931b1796.png" xlink:type="simple"/></inline-formula>. Photon number fluctuation state vectors are defined to evaluate photon number mean values, fluctuations and cross-correlation functions. These will reveal some new, i.e., unfamiliar, features originating from the full quan- tum treatment of the parametric amplification process generated by the trilinear Hamiltonian <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c6c5d6a8-3e2a-4f20-9c98-b7a0fc790cf9.png" xlink:type="simple"/></inline-formula> in Equation (1).</p><p>The signal and idler photon number operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6613ac3f-fc9f-4f97-af3f-abb438f3177f.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\51ca37e8-47fd-46fb-b505-4e430340bc26.png" xlink:type="simple"/></inline-formula> generally used in studying photon statistics in the parametric amplification process in quantum optics [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref12">12</xref>] -[<xref ref-type="bibr" rid="scirp.46476-ref15">15</xref>] are defined by</p><disp-formula id="scirp.46476-formula1553"><label>(17a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e0ec83b5-16e5-4568-b8d0-29e226ae4e64.png"/></disp-formula><p>Setting<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\80af91f9-8c45-4610-888f-a6e45c0db042.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f46c1ede-dd5d-4cbe-8fcd-118ca01ce00b.png" xlink:type="simple"/></inline-formula>in Equation (16b), using the definitions from Equation (17a) and applying Eq- uations (14b), (14c) and their Hermitian conjugates, together with Equations (15a)-(15e), gives the signal and idler photon number fluctuation state vectors <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4739bbbf-92ac-4042-b5bd-fa3768c7cd34.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c6967817-b937-433b-8d64-3fc26d1fe492.png" xlink:type="simple"/></inline-formula>, respectively in the final form</p><disp-formula id="scirp.46476-formula1554"><label>(17b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\609a3091-b16e-43ce-93a3-39607f4539a8.png"/></disp-formula><disp-formula id="scirp.46476-formula1555"><label>(17c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0187eddb-f217-43bf-a365-2951bb8fa0c0.png"/></disp-formula><p>where</p><disp-formula id="scirp.46476-formula1556"><label>(17d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d83a3b29-62ab-42aa-a5a8-67353ecedec1.png"/></disp-formula><p>The photon number fluctuation state vectors in Equations (17b), (17c) are used in the general definitions in Equations (16c) and (16e) with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\09cbbace-6c7b-4f94-bc9a-4ff982e432d5.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c26136d0-9c9a-4282-85c9-06ffa2ab95cb.png" xlink:type="simple"/></inline-formula>to obtain the mean signal and idler photon numbers <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3b64034d-3f3a-480d-83b8-332d30e37b8c.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\801fa3e7-6edc-4205-a8ca-3cc7f6b7d006.png" xlink:type="simple"/></inline-formula> and their corresponding fluctuations in the Fock state in the final forms</p><disp-formula id="scirp.46476-formula1557"><label>(18a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d6ec02c9-b0d5-4d71-9314-79f3b0851140.png"/></disp-formula><disp-formula id="scirp.46476-formula1558"><label>(18b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ad624c68-6c19-464a-bcfc-f2cc50d8b8db.png"/></disp-formula><disp-formula id="scirp.46476-formula1559"><label>(18c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6ec2dc4d-6799-4333-85fe-0a074bd09221.png"/></disp-formula><p>Finally, using equations (17b)-(17c) in the general definition in Equations (16f)-(16h) with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\feb3535e-8fc5-4cb2-8f2d-958416e231f2.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d7826278-4126-48d1-b744-16f50150f33a.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ba0cde40-81e5-49c8-b1f1-6fc621051a73.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4c1db265-39f7-4e1c-b0a0-a755ac190660.png" xlink:type="simple"/></inline-formula>, easily gives the signal-idler photon number cross-correlation functions  <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a9adcf43-2970-4d81-8593-9721fde82496.png" xlink:type="simple"/></inline-formula> and the corresponding fluctuation in the Fock state in the form</p><disp-formula id="scirp.46476-formula1560"><label>(19a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1ec6b345-1c9f-4db8-b752-1f38f5062e17.png"/></disp-formula><disp-formula id="scirp.46476-formula1561"><label>(19b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f9911d7b-3012-49e9-9277-d5f108f34056.png"/></disp-formula><disp-formula id="scirp.46476-formula1562"><label>(19c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\2f8b8e8c-94c3-48d3-bb4c-9fde65894f6e.png"/></disp-formula><sec id="s4_1"><title>4.1. New Features in Signal-Idler Photon Statistics</title><p>Substituting<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0ddd4e30-a219-45a5-8e75-120da39f128b.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\70cdc315-cb94-463f-b2f0-56cbc7587d4f.png" xlink:type="simple"/></inline-formula>and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d56cbe4d-4137-4750-b5a6-62e6552d1a86.png" xlink:type="simple"/></inline-formula> from Equations (15a)-(15c) into Equation (18a), the mean signal and idler pho- ton numbers are expressed in the explicit form</p><disp-formula id="scirp.46476-formula1563"><label>(20a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a0d2fff1-97bf-432e-88dc-ce77f04b524a.png"/></disp-formula><p>+<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9c284717-2a79-4f5f-a8b9-4cba975f4b68.png" xlink:type="simple"/></inline-formula> (20b)</p><p>which display some new, i.e., unfamiliar, features of signal-idler photon statistics appearing in the dynamics of a fully quantized parametric amplification process.</p><p>According to Equation (20a), the mean signal photon number <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4730a3f7-8b2c-44b2-a6af-f744dce19da3.png" xlink:type="simple"/></inline-formula> evolves over two different time scales specified by <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7315e25d-c1c9-44ee-8cac-481fc4916b3c.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\278b9e35-609c-4a7f-8923-1f4848aee299.png" xlink:type="simple"/></inline-formula>. The physical consequence is that for values <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d0bd5bc7-63df-4317-8f80-0c9a237a1197.png" xlink:type="simple"/></inline-formula> such that</p><disp-formula id="scirp.46476-formula1564"><label>(20c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e426973a-2a26-4488-b29f-bc93849fe70e.png"/></disp-formula><p>with</p><disp-formula id="scirp.46476-formula1565"><label>(20d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\dec0d9e9-0a2b-4edf-8f19-778b80f7ec4d.png"/></disp-formula><p>the time evolution becomes oscillatory and the beating of competing oscillations over the two time scales gene- rates fractional revivals in the mean signal photon number as demonstrated in <xref ref-type="fig" rid="fig1">Figure 1</xref>.</p><p>On the other hand, Equation (20b) shows that the mean idler photon number <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\876b6037-1e3e-484f-94a6-5659a4ce0e1b.png" xlink:type="simple"/></inline-formula> evolves over a single time scale specified only by <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6ead0b09-9140-42a1-ad65-cfcaed182311.png" xlink:type="simple"/></inline-formula> so that for values <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c2824fd6-c078-4cb2-96a9-534b7f4b6d24.png" xlink:type="simple"/></inline-formula> (implies<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\68adb3ca-cc8c-4e62-b8a9-cfa64671d4d9.png" xlink:type="simple"/></inline-formula>), the time evolution of the mean idler photon number is composed of simple oscillations as demonstrated in <xref ref-type="fig" rid="fig2">Figure 2</xref>.</p><p>These results show that signal and idler photon numbers have different modes of behavior, which may also account for the difference in number fluctuations in Equations (18b) and (18c).</p><p>The second very important feature arising as a consequence of the different time evolution patterns in Equa- tions (20a)-(20b) is the unexpected time evolution of the mean signal-idler photon number difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e7f27bb7-614b-4808-a46b-76e3de0d0105.png" xlink:type="simple"/></inline-formula> in the form</p><disp-formula id="scirp.46476-formula1566"><label>(20e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3c96ec5d-eb41-4ac2-a58d-166b29cc55bb.png"/></disp-formula><p>This result contradicts the expected conservation of the mean signal-idler photon number difference,</p><p><inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ff3df8a0-4ccc-4137-8eb9-b4dca336b426.png" xlink:type="simple"/></inline-formula>, generally obtained in the parametric/semi-classical approximation and inferred through the com- mutation of the corresponding number difference operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c5244113-cba4-4506-9326-0768fe6db65e.png" xlink:type="simple"/></inline-formula> with the bilinear or trilinear Hamiltonian (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e2be0760-52c6-4ed3-a885-d4a35519ba93.png" xlink:type="simple"/></inline-formula>) of the parametric amplification process [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref2">2</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref13">13</xref>] -[<xref ref-type="bibr" rid="scirp.46476-ref16">16</xref>] . The time variation of <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8a81d4d7-e086-40d6-916d-710489adca37.png" xlink:type="simple"/></inline-formula></p><fig id="fig1"><label>Figure 1</label><caption><p> Signal number <img src="htmlimages\16-7501380x\9743805b-c81d-4d7e-b073-e244b591923a.png" width="51.25" height="41.25" /> in (20a) over scaled time τ = gt, n = 3, k = 5, <img src="htmlimages\16-7501380x\3957fdb4-0556-4514-8c52-a36b35296e4d.png" width="60" height="33.75" />,<img src="htmlimages\16-7501380x\8b95514c-f034-40bc-a219-22a8e3c22b70.png" width="61.25" height="33.75" /></p></caption><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\631d42c3-8ba8-4ddc-a171-5b00c708125a.png"/></fig><fig id="fig2"><label>Figure 2</label><caption><p> Idler number <img src="htmlimages\16-7501380x\d5911236-9b80-4c4b-a487-1377897012e0.png" width="55" height="38.75" /> in (20b) over scaled time τ = gt, n = 3, k = 5, <img src="htmlimages\16-7501380x\bee4a4a7-8eb2-4f06-bb03-c65b7b8757af.png" width="60" height="33.75" />,<img src="htmlimages\16-7501380x\86455096-0415-4c23-a0e4-fb198cd7883f.png" width="62.5" height="33.75" /></p></caption><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fe6605f7-df4e-4f70-8873-65663b467a5f.png"/></fig><p>emerges here as a new feature of the dynamics of a fully quantized parametric amplification process. The imme- diate physical implication is that the time varying <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\82bf7598-d929-48b5-8892-f1df249f8cee.png" xlink:type="simple"/></inline-formula> does not account for the experimentally or nu- merically observed simultaneous production of signal and idler photon pairs in a parametric amplification process. This observation may also be supported by the fact that the differing photon number fluctuations in Equations (18b)-(18c) mean that the measurements of signal and idler photon numbers involve different quan- tum noise levels, which can cause delays in the counts of either signal or idler photons. The important pheno- menon of simultaneous production of signal and idler photons is addressed through photon polarization state dynamics in the next section.</p><p>The third important feature follows from the results in Equations (19a)-(19b), which show that the signal-idler photon number cross-correlation functions are generally complex, with <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3a7f44a7-d53b-4510-ac14-b186604c6554.png" xlink:type="simple"/></inline-formula> being the complex conjugate of<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9b2a105a-9566-491a-b429-2882c8b206c4.png" xlink:type="simple"/></inline-formula>. According to the definitions of the c-number variables<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5f00584a-b918-4388-9c2a-6727db13e8e7.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\02651a8a-7e28-4df1-8fc5-5ff196a942de.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6ca28ede-c3cd-44f9-8308-d3842df04654.png" xlink:type="simple"/></inline-formula>in Equations (15a), (15c) and (17d), the complex form of the number cross-correlation functions is an off-resonance feature associated with non-zero values of the frequency detuning parameter k, i.e., <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\07ca4293-6ff9-4bac-a6bd-73e6304edea9.png" xlink:type="simple"/></inline-formula>is complex for<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3cf1f9c4-b486-4f71-884c-50e4b088e866.png" xlink:type="simple"/></inline-formula>, otherwise, the signal-idler photon number cross-correlation functions are real under the resonance condition,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d6e82bb0-b3a7-44e7-a073-f05478b2cff4.png" xlink:type="simple"/></inline-formula>. Calculations performed under the resonance condition do not reveal the complex form of the signal-idler photon number cross-correlation functions.</p><p>The average signal-idler photon cross-correlation function denoted here by <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\03d262b7-c496-42af-b318-beb9eabc4544.png" xlink:type="simple"/></inline-formula> is obtained as</p><disp-formula id="scirp.46476-formula1567"><label>(21a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\68c576c8-549d-45aa-9cf3-8ce6beff61a0.png"/></disp-formula><p>which on substituting Equation (19a) and its complex conjugate in accordance with Equation (19b) becomes</p><disp-formula id="scirp.46476-formula1568"><label>(21b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1a584275-67c0-4f3d-a0fc-8ed6f5c65c8c.png"/></disp-formula><p>It is interesting to introduce the polar forms</p><disp-formula id="scirp.46476-formula1569"><label>(22a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a7d7ee36-f2ae-4cbb-adbc-86dbd4d48265.png"/></disp-formula><p>to express Equation (21b) in the convenient form</p><disp-formula id="scirp.46476-formula1570"><label>(22b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f215bcab-cea7-47d4-9f82-8de3d77b33b9.png"/></disp-formula><p>after introducing interaction parameter dependent phase differences <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e3883df7-1ea1-4500-beb6-1eccc9ebe524.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\809b4181-d31b-4faa-a424-c373c7e235e9.png" xlink:type="simple"/></inline-formula> defined by</p><disp-formula id="scirp.46476-formula1571"><label>(22c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0016f993-1c3e-4be1-bf6f-8823f3f23b7f.png"/></disp-formula><p>The amplitudes and phase angles (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\65dbd79e-99de-4ba7-9e76-f87e445e9f3f.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e9bfbd72-f91f-48ed-9bca-79cb58cc1b1a.png" xlink:type="simple"/></inline-formula>), (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8cf2148f-0157-4743-9998-51d4ab870724.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a0a76025-b852-4cc2-913c-05d935516385.png" xlink:type="simple"/></inline-formula>) and (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b1e9bd26-4cee-4b12-b7ff-fb31ed7ee901.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\da0f7967-e556-447e-8058-d91dcded7fc1.png" xlink:type="simple"/></inline-formula>) are obtained using Equations (15a), (15c) and (17d), respectively, in the form</p><disp-formula id="scirp.46476-formula1572"><label>(22d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e011af3f-62d7-4bd8-8756-f989c09907a8.png"/></disp-formula><disp-formula id="scirp.46476-formula1573"><label>(22e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\159ab353-baac-4946-9a88-18d30dd652cd.png"/></disp-formula><disp-formula id="scirp.46476-formula1574"><label>(22f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a2f8182e-6d00-4b3c-b0cf-95a3604a34c1.png"/></disp-formula><p>It is clear that the phase angles vanish under the resonance condition k = 0 and the number cross-correlation function as presented in Equations (22b)-(22c) becomes real. But, for off-resonance dynamics with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\689395d8-49da-4dbb-bc83-7522b8519b84.png" xlink:type="simple"/></inline-formula>, Equ- ation (22b) shows that the signal-idler photon number cross-correlation function is characterized by an interfe- rence phenomenon controlled by interaction parameters. It is an interesting interference phenomenon characte- rized by two generally unequal phase differences <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\708dd2ee-db4a-4bfb-9de7-bffe424ce35d.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d3e557da-5746-4af0-8836-6a6b784021d5.png" xlink:type="simple"/></inline-formula>. The interference phenomenon in the off-reson- ance signal-idler photon number dynamics may also have some constructive or destructive effect on the ex- pected simultaneous production of signal and idler photons.</p></sec><sec id="s4_2"><title>4.2. Recalling the Parametric/Semi-Classical Approximation</title><p>An important observation is that the time variation of the mean signal-idler photon number difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\11542f71-e95e-420a-9379-722bad3fa20f.png" xlink:type="simple"/></inline-formula> and the complex form yielding the interference phenomenon in the signal-idler photon number cross-correlation function <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8b29980a-82a3-463c-8778-4960a18085d1.png" xlink:type="simple"/></inline-formula> are both quantum effects characterizing the dynamics of a fully quantized parametric amplification process. These effects do not appear in the parametric/semi-classical approximation.</p><p>In the parametric approximation or semi-classical model where the pump photon is considered to be generated by a high intensity laser field, the mean pump photon number n is obtained from a c-number field amplitude α of very large magnitude according to</p><disp-formula id="scirp.46476-formula1575"><label>(22g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\42789361-1902-4be2-966e-cfab9e0ab221.png"/></disp-formula><p>from which follows</p><disp-formula id="scirp.46476-formula1576"><label>(22h)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\baf3ba35-8c87-4f5d-9162-dc3e1156e1fa.png"/></disp-formula><p>Using Equation (22h) in Equations (18a) and (19a) gives the mean photon numbers, number difference and cross-correlation function in the parametric approximation/semi-classical model in the familiar forms [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.46476-ref16">16</xref>]</p><disp-formula id="scirp.46476-formula1577"><label>(22i)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3c123e36-eb59-4123-b9a6-c92d00de8855.png"/></disp-formula><disp-formula id="scirp.46476-formula1578"><label>(22j)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\66d44268-d712-4d50-8d31-5eb704cd44d5.png"/></disp-formula><disp-formula id="scirp.46476-formula1579"><label>(22k)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5406f84b-ccd4-4543-86a8-7189b70799ad.png"/></disp-formula><p>Using Equation (22h) in Equations (18b)-(18c) and comparing the results with Equation (22k) gives the num- ber fluctuations in the parametric/semiclassical approximation in the form</p><disp-formula id="scirp.46476-formula1580"><label>(22l)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\aea89fc5-3761-4ff4-9661-e8d65e6863f0.png"/></disp-formula><p>These results show that, in the parametric approximation or the semi-classical model, the mean signal-idler photon number difference is conserved according to Equations (22i), (22j) and the number cross-correlation function is real according to Equation (22k). The simultaneous production of signal and idler photons predicted within the parametric/semi-classical approximation is based on Equations (22j) and (22l) [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] .</p><p>The above results confirm that the complex forms and the time variation obtained in Equations (19a) and (20e), respectively, emerge entirely as quantum effects in the fully quantized parametric amplification process.</p><p>The main conclusion drawn from the investigation in this section is that the signal and idler photon number operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0de6830d-5d1f-4c5b-b4d3-3f3c49d41e49.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d36223e3-7b29-4618-a0d8-0bf3004614b0.png" xlink:type="simple"/></inline-formula> are not well-behaved and are therefore not suitable dynamical operators for study- ing photon statistics in a fully quantized parametric amplification process. The non-conservation of the mean number difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\cab7698b-b456-4712-8978-433ac12d6ba1.png" xlink:type="simple"/></inline-formula> is inconsistent with the commutation relation<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\91c526a9-ebf5-4e06-ba2d-329047116ca2.png" xlink:type="simple"/></inline-formula>, which shows that the number operator difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8eb42cdd-4885-45bd-9a3a-11922b60d2c4.png" xlink:type="simple"/></inline-formula> is a constant of the motion, while the number cross-correlation function <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0fb5e329-480f-4314-86c3-46b783c97534.png" xlink:type="simple"/></inline-formula> is generally complex and experiences an interference phenomenon. In addition, comparing the re- sults obtained within the full quantum treatment in Equations (19a), (20e) with the results obtained within the parametric/semi-classical approximation in Equations (22j), (22k) as appropriate reveals contradictions between number-based photon statistics determined in the fully quantized and in the parametric/semi-classical approxi- mation models of the parametric amplification process. Polarized signal-idler photon intensity operators are identified to be the well-behaved dynamical operators for studying photon statistics in parametric amplification/ down-conversion processes in the next section.</p></sec></sec><sec id="s5"><title>5. The Polarization Operators and Symmetry Group of the Parametric Amplification Process</title><p>This section establishes that the appropriate dynamical operators which characterize the dynamics and specify the dynamical symmetry group of the parametric amplification process are the polarization operators  <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\7fbba546-433a-4608-aa61-83326671ffdc.png" xlink:type="simple"/></inline-formula> derivable from the polarization operator vector <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5f937025-0694-45e6-9eea-b58d1fc66a57.png" xlink:type="simple"/></inline-formula> and its Hermitian conjugate <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1dfb2258-aa42-4f22-bad2-e82a37beaeb9.png" xlink:type="simple"/></inline-formula> ac- cording to</p><disp-formula id="scirp.46476-formula1581"><label>(23a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\09b32197-ce45-4d3c-bee9-464a2347954a.png"/></disp-formula><p>where</p><disp-formula id="scirp.46476-formula1582"><label>(23b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\72c04080-8d61-4b44-af8b-b27ff61161c6.png"/></disp-formula><p>and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\a545c5d2-d418-4e90-8b52-d0fe66ab2ab4.png" xlink:type="simple"/></inline-formula> are the usual Pauli spin operators defined according to</p><disp-formula id="scirp.46476-formula1583"><label>(23c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\885eaf3f-18a1-4e36-ab03-8302a810d90c.png"/></disp-formula><disp-formula id="scirp.46476-formula1584"><label>(23d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8559d5c3-c630-4a5e-aff0-19d1e7971d4a.png"/></disp-formula><p>Using Equations (23c), (23d) in Equation (23a) provides the desired polarization operators in the form</p><disp-formula id="scirp.46476-formula1585"><label>(24a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\360cd0f5-1f93-47b1-987c-13d482a53f77.png"/></disp-formula><disp-formula id="scirp.46476-formula1586"><label>(24b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\33f723fd-728c-4946-9517-a09f61233752.png"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bd5ffd8c-155f-4435-b912-06971155d6b8.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\67dc3d58-578a-4aaa-b6c5-b947660d2a61.png" xlink:type="simple"/></inline-formula> are the positive and negative helicity intensity operators defined earlier in Equation (7g).</p><p>Application of the usual commutation relations between the annihilation and creation operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f82718a5-9fe0-4da4-b7e1-287877e131a1.png" xlink:type="simple"/></inline-formula> provides the algebraic relations</p><disp-formula id="scirp.46476-formula1587"><label>(24c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\9efb0e84-dc34-4d1e-a12e-4fb56bc2a98f.png"/></disp-formula><disp-formula id="scirp.46476-formula1588"><label>(24d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\07fe9697-ad88-48a6-9dfc-b99ca18b97a6.png"/></disp-formula><p>which constitute the Lie algebra of the <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c57f4bc2-f9ca-46b3-a0c7-5491f34a6879.png" xlink:type="simple"/></inline-formula> symmetry group. By Equation (24d), <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4519a827-8ee7-4298-92c9-222490fedcad.png" xlink:type="simple"/></inline-formula>commutes with all the other operators and may be identified with the identity operator in <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\70f0f68f-b040-4296-b883-d3e0717c1aff.png" xlink:type="simple"/></inline-formula> algebra. The set of polarization operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1a722ec6-987e-4cc4-8afb-e0d2516d069f.png" xlink:type="simple"/></inline-formula> defined in Equations (24a), (24b) therefore constitute the continuous variable genera- tors of the <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0806310f-fc1d-4e89-9d81-e7e6abea8bcc.png" xlink:type="simple"/></inline-formula> symmetry group covering the dynamics of the non-degenerate parametric amplification process. The polarization operators thus specify the Lie group <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\09f6e141-35b1-4411-a44d-97a9534d75d5.png" xlink:type="simple"/></inline-formula> as the dynamical symmetry group of the parametric amplification/down-conversion process. The polarization states of the coupled signal-idler photon pairs are therefore appropriately specified by points on the two-sheet hyperboloid of the <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\47028770-e278-42cc-b596-a5bd44143597.png" xlink:type="simple"/></inline-formula> manifold.</p><p>Using Equations (24a), (24b) in Equation (1) puts the Hamiltonian H in the form</p><disp-formula id="scirp.46476-formula1589"><label>(24e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3ce78ce3-77f9-419e-807b-1c3fce500706.png"/></disp-formula><p>where the angular frequency difference <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\37fbc9ba-1add-4d48-aa01-eea3c4763aa3.png" xlink:type="simple"/></inline-formula> and sum <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\338cc9af-35ce-4897-9585-480f6bdfedfc.png" xlink:type="simple"/></inline-formula> are as defined earlier in Equation (6b). An inconse- quential constant term <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\90ee0ea6-30fa-4773-8819-b5f7ad6d2863.png" xlink:type="simple"/></inline-formula> in <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\104c0a33-fc04-4694-ae08-eb166d82fcd5.png" xlink:type="simple"/></inline-formula> has been ignored. Application of Equation (24d) gives the important result</p><disp-formula id="scirp.46476-formula1590"><label>(24f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\52ef6eb5-3782-40dc-9254-afb8c734ac9a.png"/></disp-formula><p>which leads to the conclusion that the polarization operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\956332c2-e77d-4bac-831c-9e0ec83b971d.png" xlink:type="simple"/></inline-formula> is a constant of the motion specifying a con- servation law governing the dynamics of the coupled signal-idler photon pairs in the fully quantized parametric amplification process. The polarization operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\63301d95-8641-4227-bfa3-3acc6fc7d1b9.png" xlink:type="simple"/></inline-formula> will be treated as a well-behaved dynamical operator if its mean value is conserved to maintain consistency with the result in Equation (24f). This is established below.</p><sec id="s5_1"><title>5.1. Intensity Fluctuation State Vectors</title><p>It is necessary to study the behavior of the intensity operators which constitute the polarization operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8b932cd7-34c4-4119-8efd-b8327a5fcb04.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\00ecfd04-0c9e-46fe-9a3f-181db33c7d6b.png" xlink:type="simple"/></inline-formula> according to Equation (24a). The definitions of the time evolving positive and negative helicity inten- sity operators <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\698c7fcc-6e34-43bb-b327-3b114d42ed3a.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0662afae-cacb-4234-abab-5137f87ec8bb.png" xlink:type="simple"/></inline-formula> for the coupled polarized signal-idler photon pairs follow from Equation (7g) in the form</p><disp-formula id="scirp.46476-formula1591"><label>(25a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bdbf90fb-139e-43d6-9baa-1348ee0a693d.png"/></disp-formula><p>The time evolving positive and negative helicity intensity fluctuation state vectors <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1e05a9ea-d7b3-492d-85ff-8589bc81ca98.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\aa20df16-dde4-461e-9800-0ca5e71a850e.png" xlink:type="simple"/></inline-formula>, re- spectively are easily obtained using Equations (14b), (14c), (25a) and the general definition in Equation (16b) with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1a03f28b-789b-4d46-9b88-106f14202b0c.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\811351e7-a5c9-42b7-90ed-ed78a1fd197a.png" xlink:type="simple"/></inline-formula>in the final form (noting<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\dcf8cb67-be20-4665-9606-cef1a662e26a.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\25486702-b4b5-4d11-a553-d81127cf6dfe.png" xlink:type="simple"/></inline-formula>)</p><disp-formula id="scirp.46476-formula1592"><label>(25b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\415704e3-5c32-45e7-a97f-7223eaeee792.png"/></disp-formula><disp-formula id="scirp.46476-formula1593"><label>(25c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\73152d07-a9a1-4166-b5db-44c4bc66e834.png"/></disp-formula><p>Using the intensity fluctuation state vectors from Equations (25b), (25c) according to the general definitions in Equations (16c) and (16e) with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d2e41bda-4ad7-47be-b3b8-cf30f1001ada.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\aae62d8a-8a00-45e9-a481-927f6cf07c5c.png" xlink:type="simple"/></inline-formula>, the mean values and corresponding fluctuations of the positive and negative helicity intensities<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6ac74213-3c68-40c2-ae71-0f98e0043759.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bc062b9c-cf66-47d8-9457-d9487946be34.png" xlink:type="simple"/></inline-formula>in the Fock state are obtained in the final forms</p><disp-formula id="scirp.46476-formula1594"><label>(26a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4d521fdd-c94c-42b8-a45c-273ac081104b.png"/></disp-formula><disp-formula id="scirp.46476-formula1595"><label>(26b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6b9c3a92-bbf8-477a-80ed-a3af3ae9b9c2.png"/></disp-formula><p>The positive and negative helicity intensity cross-correlation functions and cross-correlation fluctuations are obtained using Equations (25b)-(25c) and the general definitions in Equations (16f) and (16h) with<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f6b690f5-3132-4a6e-ba34-e593a87c3683.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e8100c15-7416-4949-bafd-0a686bfa923c.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ec6b195b-7280-4e56-8c36-a8155a8ceff5.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\0b9c214d-b49f-4ebf-a1f3-5efb1bd78289.png" xlink:type="simple"/></inline-formula>in the final form</p><disp-formula id="scirp.46476-formula1596"><label>(26c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6e252487-e8e3-48cb-8910-b79b416276de.png"/></disp-formula><disp-formula id="scirp.46476-formula1597"><label>(26d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\be98ecf8-735c-47c8-9767-85fd3778762c.png"/></disp-formula><p>Comparing Equations (26b) and (26d) gives the important result</p><disp-formula id="scirp.46476-formula1598"><label>(26e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e78794e4-5acc-41cb-ad26-13d9978a4009.png"/></disp-formula><p>Two important features characterizing the coupled signal-idler photon polarization state dynamics follow from the results in Equations (26a) and (26e). The results in Equation (26a) give the mean positive and negative helic- ity intensity difference as</p><disp-formula id="scirp.46476-formula1599"><label>(27a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1b96e64f-95a0-49ba-9151-da458c135943.png"/></disp-formula><p>which on using <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b42b1db1-11ca-49c8-8f9d-31261b64d990.png" xlink:type="simple"/></inline-formula> from Equations (15a)-(15d) to obtain</p><disp-formula id="scirp.46476-formula1600"><label>(27b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\097c33d4-753b-4a3a-9c18-95d29b8404de.png"/></disp-formula><p>provides the conservation law</p><disp-formula id="scirp.46476-formula1601"><label>(27c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\554fd28d-4fa1-4123-97c4-39e59d42b536.png"/></disp-formula><p>where<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\182f5a97-607d-4008-ba1f-cda8fbb5196a.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e99d92c9-44de-4be7-9baa-54e206616b80.png" xlink:type="simple"/></inline-formula>are the respective initial mean positive and negative helicity intensities. The result in Equation (26e) gives the cross-correlation coefficient</p><disp-formula id="scirp.46476-formula1602"><label>(27d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ea150aba-cb8b-48e3-ac6d-d7cba96e0588.png"/></disp-formula><p>The two results in Equations (27c) and (27d) show that in the fully quantized parametric amplification process, polarized signal and idler photons in the positive and negative helicity states are produced simultaneously.</p></sec><sec id="s5_2"><title>5.2. Polarization Fluctuation State Vectors</title><p>Using the results and general definitions obtained above as appropriate give the polarization fluctuation state vectors<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b8631790-7be4-477a-a29c-851fdb8f063d.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\45355a5b-b71e-453f-9a48-eacbdfe4734c.png" xlink:type="simple"/></inline-formula>in the form</p><disp-formula id="scirp.46476-formula1603"><label>(28a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fb3a2915-24b5-4f5a-a586-059611fda98f.png"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\438a510e-e396-413e-8b67-2e2e9c25601c.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8c41ca97-9f43-470b-adca-064d8eb00de5.png" xlink:type="simple"/></inline-formula> are already obtained in Equations (25b) and (25c), respectively, while the fluctua- tion state vectors <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b93d03bf-cf96-424b-92c6-978eb28a6084.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\498af37a-7cec-4187-b341-74b58f53b864.png" xlink:type="simple"/></inline-formula> defined by</p><disp-formula id="scirp.46476-formula1604"><label>(28b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ae6ddf2d-9d09-4b0f-956a-a3c1b86c5ac0.png"/></disp-formula><p>take the final form (noting<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\67a970aa-867c-48b0-8205-16f6e0a30703.png" xlink:type="simple"/></inline-formula>,<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\8aae2d1c-ad93-4120-9a37-f738e5b790f1.png" xlink:type="simple"/></inline-formula>)</p><disp-formula id="scirp.46476-formula1605"><label>(28c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\2294d5f5-1460-4aa8-a5ae-250526a12b15.png"/></disp-formula><disp-formula id="scirp.46476-formula1606"><label>(28d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d72e8c74-45f2-4c3d-988e-5c43b065de63.png"/></disp-formula><p>The mean values of the time evolving polarization operators in the Fock state are easily obtained using the general definitions as</p><disp-formula id="scirp.46476-formula1607"><label>(29a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\62b5d52d-861c-4b51-a65c-c430b9288a97.png"/></disp-formula><disp-formula id="scirp.46476-formula1608"><label>(29b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\adbcca04-96c0-46fa-b08b-861e019989a5.png"/></disp-formula><p>where <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b07e4457-bf2b-4804-8e59-09243e950908.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\ed56cfef-5fdf-403b-ba12-d1f5d2a960c4.png" xlink:type="simple"/></inline-formula> are the mean positive and negative helicity intensities obtained earlier in Equation (26a).</p><p>Using Equations (15a)-(15d) in Equation (26a) and substituting the results into Equation (29a) gives</p><disp-formula id="scirp.46476-formula1609"><label>(29c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f8496b47-57b1-4202-877e-2152a17fac82.png"/></disp-formula><disp-formula id="scirp.46476-formula1610"><label>(29d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fffc85e6-727a-4b75-b9cc-47487a7c081a.png"/></disp-formula><p>It is clear from Equation (29c) that the mean value <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b6c1cc24-4bd2-4c20-a7a6-ce6a486c5a60.png" xlink:type="simple"/></inline-formula> evolves in time over two different time scales specified by <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\dd255fdd-4ad7-47ee-a262-9724a5fd2017.png" xlink:type="simple"/></inline-formula> and<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\fa3759b1-dbff-4f63-818b-4f9296897fba.png" xlink:type="simple"/></inline-formula>, which for <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\6a6bb9b9-a231-4e76-9d18-4a8f05ef181f.png" xlink:type="simple"/></inline-formula> develops into an oscillatory evolution cha- racterized by fractional revivals due to the beating of oscillations over the two time scales. This behavior takes exactly the form demonstrated in <xref ref-type="fig" rid="fig1">Figure 1</xref>.</p><p>The result in Equation (29d) shows that<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\910f45ad-0fb5-4547-9617-8cc3b37f1383.png" xlink:type="simple"/></inline-formula>, which according to the definition in Equation (23a) for<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d8b46043-3135-4c26-86fa-26e613434742.png" xlink:type="simple"/></inline-formula>, also defines the mean intensity inversion between the positive and negative helicity states, is conserved in time. This is in complete agreement with the earlier result obtained in Equation (24f) establishing that the pola- rization operator <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\21edd686-1ae3-408f-9353-0d3a5a656137.png" xlink:type="simple"/></inline-formula> is a constant of the motion specifying a conservation law governing the dynamics of a fully quantized parametric amplification process. This consistency leads to identification of the polarization op- erator (or <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bd878639-434f-448b-8adc-eb6b69386417.png" xlink:type="simple"/></inline-formula> generator) <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\eb1774bc-6716-4fa4-9518-8706100b202c.png" xlink:type="simple"/></inline-formula>as defined in Equation (24a) as the appropriate well-behaved dynamical operator for specifying the conservation law governing the dynamics of a fully quantized parametric amplifica- tion process.</p><sec id="s5_2_1"><title>Fluctuations of the Polarization Operators</title><p>The fluctuations in <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\17985dff-f963-4b18-a768-183a771b350f.png" xlink:type="simple"/></inline-formula> and <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\513f0499-5f5a-4e30-bcad-7d0d8c7818df.png" xlink:type="simple"/></inline-formula> are easily obtained in the form</p><disp-formula id="scirp.46476-formula1611"><label>(30a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\74da8559-16ee-4acd-9abc-ba7ae06e218e.png"/></disp-formula><disp-formula id="scirp.46476-formula1612"><label>(30b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1ddbadb0-3c8a-4c74-af04-974cdf8d8da9.png"/></disp-formula><p>after applying the definitions of fluctuations in the intensities and cross-correlation functions obtained earlier. Application of Equation (26e) in Equations (30a), (30b) gives the final results</p><disp-formula id="scirp.46476-formula1613"><label>(30c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d5b7c3ca-87b2-4e07-86e1-bc47374a949a.png"/></disp-formula><disp-formula id="scirp.46476-formula1614"><label>(30d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\1bbaa5e8-2b9f-41c6-9482-7d796cf489d9.png"/></disp-formula><p>Noting that</p><disp-formula id="scirp.46476-formula1615"><label>(31a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\554fb613-b690-4a42-9b87-0d9ee6e11ff8.png"/></disp-formula><p>the second moments<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f1b4b193-d7db-4712-a149-26c9c36489dc.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\716bd6bc-0eab-4e12-a837-6fb3edddfc0b.png" xlink:type="simple"/></inline-formula>and cross-correlation functions<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\d6a59f5f-d382-43f6-8933-d6a9e5502a49.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b8039142-f4df-4ccd-a0bf-2cde07c82cc3.png" xlink:type="simple"/></inline-formula>are defined by</p><disp-formula id="scirp.46476-formula1616"><label>(31b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5204ab89-da20-4847-a200-958034e84504.png"/></disp-formula><disp-formula id="scirp.46476-formula1617"><label>(31c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\bd34664a-d752-40ed-92d6-76b186d6538f.png"/></disp-formula><disp-formula id="scirp.46476-formula1618"><label>(31d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\21543fea-c94c-4c2b-be59-b6bcd4ded2ca.png"/></disp-formula><p>where Equations (31c), (31d) are noted to define some commonly calculated cross-correlation functions ex- pressed in normal or anti-normal order [<xref ref-type="bibr" rid="scirp.46476-ref1">1</xref>] . Using Equations (28c), (28d) gives</p><disp-formula id="scirp.46476-formula1619"><label>(31e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\f26cf157-4637-44df-8318-91e1a8122813.png"/></disp-formula><disp-formula id="scirp.46476-formula1620"><label>(31f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b9c068a3-61cf-4e5b-9fa1-88834afdad14.png"/></disp-formula><disp-formula id="scirp.46476-formula1621"><label>(31g)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e4037cc4-152c-43bd-9032-039dc27d105f.png"/></disp-formula><p>The fluctuations follow easily in the form</p><disp-formula id="scirp.46476-formula1622"><label>(32a)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\dc8889c3-f1f5-42ff-b7a4-7a413d3b0a95.png"/></disp-formula><disp-formula id="scirp.46476-formula1623"><label>(32b)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\4a023a45-29b8-4742-9736-2797289f5039.png"/></disp-formula><p>Finally, the definitions of<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\028337a4-6861-4762-94f8-4f922892933f.png" xlink:type="simple"/></inline-formula>, <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b75b9bdb-4154-47c5-86a5-c3feb621608e.png" xlink:type="simple"/></inline-formula>in Equation (24b) easily gives the corresponding fluctuation state vectors, mean values and fluctuations in the respective forms (recalling Equation (31a)).</p><disp-formula id="scirp.46476-formula1624"><label>(32c)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\addac065-fe50-478b-ab2d-4146bb46a455.png"/></disp-formula><disp-formula id="scirp.46476-formula1625"><label>(32d)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\3015e60d-5aea-405d-8fcd-472c5cd72680.png"/></disp-formula><disp-formula id="scirp.46476-formula1626"><label>(32e)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\c836af2f-47b9-4409-9da8-24f43163a289.png"/></disp-formula><disp-formula id="scirp.46476-formula1627"><label>(32f)</label><inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\b7ef44c9-a56b-4a2c-a957-013ed70842fe.png"/></disp-formula><p>The time evolution of the fluctuations <inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\77048607-746f-4280-bbb6-ea194b2164f0.png" xlink:type="simple"/></inline-formula> obtained using Equations (31f), (31g) in Eq- uation (32f) is characterized by fractional revivals as demonstrated in <xref ref-type="fig" rid="fig3">Figure 3</xref>.</p></sec></sec></sec><sec id="s6"><title>6. Conclusions</title><p>This paper reveals that the internal dynamics of a fully quantized parametric amplification process is characte- rized by an (anti)-Jaynes-Cummings mode of interaction governing the time evolution of the polarization state vectors of the coupled signal-idler photon pair. The exact analytical solutions obtained in the paper have suc- cessfully revealed some uniquely quantum mechanical effects such as the unexpected time variation (non-con- servation) of the signal-idler photon number inversion (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\5a3d8841-13a0-4eee-b516-055f7f35dff5.png" xlink:type="simple"/></inline-formula>) and the complex form as well as the interference phenomenon characterizing the signal-idler number cross-correlation function under off-reson- ance dynamics. The physical implication is that the signal and idler photon number operators are not well-be- haved operators for studying photon statistics in a fully quantized parametric amplification process. In particular, the time variation of the number inversion and the interference phenomenon mean that the observed simultane- ous production of signal and idler photons is not specified by the signal-idler photon number cross-correlations as generally believed. It has been established here that the dynamics is characterized by the polarization states of the coupled signal-idler photon pairs. Polarized signal-idler photon intensity operators and the related polariza- tion operators, which specify the dynamical symmetry group (<inline-formula><inline-graphic xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\e8d106da-a9f0-4bb8-ab03-cfe59b440b4f.png" xlink:type="simple"/></inline-formula>) of the system, have been identified as the well-behaved operators for describing photon statistics in the fully quantized (as well as the semi-classical)</p><fig id="fig3"><label>Figure 3</label><caption><p> Polarization fluctuations <img src="htmlimages\16-7501380x\a96cc92c-70e7-427d-9081-08b669a9a0f3.png" width="213.75" height="50" /> in (32d) over scaled time τ = gt, n = 3, k = 5, <img src="htmlimages\16-7501380x\e48444f5-e0e6-4efc-acf6-b4850dd7f87d.png" width="60" height="33.75" />,<img src="htmlimages\16-7501380x\5815ee7d-7a4c-4a6e-b005-925ca4a9dcd0.png" width="62.5" height="33.75" /></p></caption><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://file.scirp.org/Html/htmlimages\16-7501380x\414c1c93-e9ea-42a6-8bcc-320fbb4a89ca.png"/></fig><p>parametric amplification processes. The conservation of the positive-negative helicity intensity inversion and the purely real cross-correlation function directly specify the simultaneous production of positive and negative he- licity polarized signal and idler photons. The dynamics of the fully quantized parametric amplification process has also been shown to be characterized by the fundamental quantum mechanical phenomenon of fractional re- vivals when the pump, signal and idler photons are in the initial Fock state. General collapses and revivals (not explicitly included in this paper) emerge when the pump photon is taken in an initial coherent state, as elabo- rated in [<xref ref-type="bibr" rid="scirp.46476-ref3">3</xref>] .</p><p>In general, the exact analytical expressions obtained in this paper provide opportunities for in-depth studies of the statistical properties of fully quantized parametric amplification/down-conversion processes. The concept of fluctuation state vectors, which arises from the evaluation of expectation values of time evolving operators within the Heisenberg picture, constitutes an exact quantum state engineering process [<xref ref-type="bibr" rid="scirp.46476-ref17">17</xref>] and the correspond- ing density matrices can be used to study the entanglement properties of the fully quantized parametric amplifi- cation process. The positive and negative helicity intensity operators, together with the polarization operators, are useful in the construction of intelligent state vectors on an SU(1, 1) manifold [<xref ref-type="bibr" rid="scirp.46476-ref18">18</xref>] . In particular, polarization operators are currently employed in characterization and tomography of photon polarization states, mostly under parametric interactions [<xref ref-type="bibr" rid="scirp.46476-ref19">19</xref>] -[<xref ref-type="bibr" rid="scirp.46476-ref22">22</xref>] . These are important for applications in the design and implementation of quantum information processing, quantum computation, quantum tomography and other quantum-based preci- sion technologies.</p></sec><sec id="s7"><title>Acknowledgements</title><p>I thank my colleague Dr. B. O. Ndinya for valuable support in preparation of diagrams. This work was fully supported by Maseno University.</p></sec></body><back><ref-list><title>References</title><ref id="scirp.46476-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">MANDEL, L. (1986) QUANTUM EFFECTS IN SPONTANEOUS PARAMETRIC DOWN CONVERSION OF LIGHT. IN: PIKE, E.R. AND SARKAR, S., EDS., FRONTIERS IN QUANTUM OPTICS, ADAM HILGER, BRISTOL AND BOSTON, 318.</mixed-citation></ref><ref id="scirp.46476-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">NATION, P.D. AND BLENCOWE, M.P. 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