Barros discusses that [1] Nagata derives inconsistencies from quantum mechanics [2] . Barros considers that the inconsistencies do not come from quantum mechanics, but from extra assumptions about the reality of observables. More clearly, since quantum mechanics forbids the simultaneous measurements of non-commuting observables, as they do not commute, it does not allow us to simultaneously assign values to them. The contradiction does not come from quantum mechanics, but from the assumption that we can assign values to measurements that were not performed.

Here we discuss the fact that there is a contradiction within the quantum theory. We discuss the fact that only one expected value of a spin-1/2 pure state rules out the reality of the observable. We do not accept extra assumptions about the reality of observables. We use the actually measured results of quantum measurements (raw data). We use a single Pauli observable. We stress that we can use the quantum theory even if we give up the axiomatic system for the quantum theory.

On the other hand, the double-slit experiment [3] is an illustration of wave-particle duality. In it, a beam of particles (such as photons) travels through a barrier with two slits removed. If one puts a detector screen on the other side, the pattern of detected particles shows interference fringes characteristic of waves; however, the detector screen responds to particles. The system exhibits the behavior of both waves (interference patterns) and particles (dots on the screen).

If we modify this experiment so that one slit is closed, no interference pattern is observed. Thus, the state of both slits affects the final results. We can also arrange to have a minimally invasive detector at one of the slits to detect which slit the particle went through. When we do that, the interference pattern disappears [4] . An analysis of a two-atom double-slit experiment based on environment-induced measurements is reported [5] .

We assume implementation of the double-slit experiment. There is a detector just after each slit. Thus interference figure does not appear, and we do not consider such a pattern. The possible values of the result of measurements are (in unit). If a particle passes one side slit, then the value of the result of measurement is +1. If a particle passes through another slit, then the value of the result of measurement is −1. This model is an easy detector model for Pauli observable.

Projective measurement theory does not meet Deutsch’s algorithm [6] . In this reference, the expected values of the two spin observables and cannot be measured by using projective measurement theory. And new measurement theory covers the problem. Let us follow the argumentations. Assume a pure spin-1/2

state lying in the plane. We have from the wave functional analysis of quantum mechanics. On the other hand, we have if projective measurement theory is true. This fact cannot coexist with quantum formula. Hence the expected values of two spin ob-

servables and cannot be measured by using projective measurement theory. But, we have

when the new quantum measurement theory is true. The values of the result of quantum

measurements are. We consider whether an expected value of one spin observable can be measured by using projective measurement theory. So, we investigate the relation between an easy detector model for Pauli observable and projective measurement theory.

We consider whether projective measurement theory meets an easy detector model for Pauli observable. We try to implement double-slit experiment. There is a detector just after each slit. Thus interference figure does not appear, and we do not consider such a pattern. We assume that a source of spin-carrying particles emits them in a state, which can be described as an eigenvector of Pauli observable. We consider a single expected value of Pauli observable in the double-slit experiment. A wave function analysis says that the quantum expected value of it is zero. However, the quantum predictions within projective measurement theory cannot coexist with the value of the expected value of. Hence, such projective measurement theory does not meet the easy detector model.

At this stage we are in the following situation.

・ We cannot measure an expected value of a single spin observable in a state by using projective measurement theory.

First we discuss a contradiction within the quantum theory as follows [7] .

Matrix theory is not compatible with probability theory. Matrix theory has axioms. Probability theory has axioms. These have axioms without a contradiction. Can we construct axioms for matrix theory and probability theory without a contradiction?

Let us consider joint probability. is an observable. is an observable. a, b are actually measured results of quantum measurements in a quantum state, respectively. and are not commutative. Thus,

We consider as follows: First we measure observable and get as the actually measured result. And next we measure observable and get as the actually measured result. This joint event is different if we exchange to, in general. Hence

On the other hand, the joint probability is depictured in terms of conditional probabilities:

From axioms of probability theory, we have

We cannot assign truth value “1” for the proposition (2) and for the proposition (4), simultaneously. We are in a contradiction. We cannot construct axioms for matrix theory and probability theory without the contradiction. There is a contradiction within the quantum theory.

The first point is actually that, conventional Quantum Mechanics discussions typically do not employ conditional probabilities correctly if at all. This is the central issue with Bell’s analysis leading to the idea that Quantum Mechanics requires non-locality or irreality and wave packet collapse and what not!

The two expected values of a spin-1/2 pure state and rule out the existence of probability space of von Neumann’s projective measurement [2] [6] .

In this section, we discuss the fact that only one expected value of a spin-1/2 pure state rules out the existence of probability space of von Neumann’s projective measurement.

We assume implementation of the double-slit experiment [3] . There is a detector just after each slit. Interference figure does not appear, and we do not consider such a pattern. Let be the Pauli vector. We assume that a source of spin-carrying particles emits them in a state, which can be described as an eigenvector of Pauli observable.

We consider a quantum expected value as

We introduce a hidden-variables theory for the quantum expected value of the Pauli observable. Then, the quantum expected value given in (5) can be

where is some hidden variable, is a probabilistic distribution, and is the predetermined “hidden” result of the measurement of the dichotomic observable. The possible values of are (in unit). If a particle passes one side slit, then the value of the result of measurement is +1. If a particle passes through another slit, then the value of the result of measurement is −1. It is von Neumann’s projective measurement for.

In what follows, we discuss the fact that we cannot assign the truth value “1” for the proposition (6). Assume the proposition (6) is true. We have the same proposition

An important note here is that the value of the right-hand-side of (6) is equal to the value of the right-hand- side of (7) because we only change a label.

We derive a necessary condition for the quantum expected value given in (6). We derive the possible value of the product of the quantum expected value and a delta sign. The quantum expected value is given in (6). We have

Here we use the fact

since the possible values of are. Hence we derive the following proposition if we assign the truth value “1” for a hidden-variables theory for the Pauli observable

We derive a necessary condition for the quantum expected value for the system in a pure spin-1/2 state given in (5). We derive the possible value of the product

is a delta sign. is the quantum expected value given in (5). We have the following proposition since

We do not assign the truth value “1” for two propositions (10) and (12), simultaneously. We are in a contradiction. We have to give up a hidden-variables theory for the expected value of the Pauli observable. The measured observable in the state does not have a counterpart in physical reality.

Next we discuss the fact that there is a contradiction within the quantum theory by using a single Pauli observable [8] . In this case, there is no need to argue that observables under consideration are commuting or non-com- muting. Especially, we systematically describe our assertion based on more mathematical analysis using raw data (the actually measured results of quantum measurements). In this case, there is no need to argue the reality of observables. There exists raw data because we have seen it.

We consider the relation between double-slit experiment and projective measurement. We try to implement double-slit experiment. There is a detector just after each slit. Thus interference figure does not appear, and we do not consider such a pattern. The actually measured results of quantum measurements are (in unit). If a particle passes one side slit, then the value of the actually measured result of measurement is +1. If a particle passes through another slit, then the value of the actually measured result of measurement is −1.

In conclusions, Barros has discussed that Nagata has derived inconsistencies from quantum mechanics. Barros has considered that the inconsistencies do not come from quantum mechanics, but from extra assumptions about the reality of observables. Here we have discussed the fact that there is a contradiction within the quantum theory. We have discussed the fact that only one expected value of a spin-1/2 pure state rules out the reality of the observable. We do not have accepted extra assumptions about the reality of observables. We have used the actually measured results of quantum measurements (raw data). We have used a single Pauli observable. We have stressed that we can use the quantum theory even if we give up the axiomatic system for the quantum theory.

The author thanks Professor Tadao Nakamura.