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arXiv:2603.18713 · Physical Review A

Comment on "Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements"

Juan José Seoane, Xabier Oianguren-Asua, Albert Solé, Xavier Oriols

quant-phSubmitted Mar 19, 2026• Announced Mar 20, 2026• 3 citations

Abstract

In their paper (arXiv:2402.09879), Aredes and Saldanha analyze several paradoxes related to weak values and present a "general argument" that aims to show that "realistic interpretations ...of weak values lead to inconsistencies". Although we agree with the identified inconsistencies for the specific weak values analyzed there, in this Comment we demonstrate that the origin of these inconsistencies is not their general argument, which is formally incorrect. We use Bohmian mechanics as a counterexample to confirm that their conclusions are not valid for all weak values and quantum theories. In particular, we show that weak values postselected in position can in fact be interpreted within Bohmian mechanics as properties of quantum systems, detached from any measuring devices, in a consistent and meaningful way.

Journal reference: Phys. Rev. A 111 (2025) 066201
DOI: 10.1103/PhysRevA.111.066201
Comments: 5 pages, 0 figures. Comment on arXiv:2402.0987

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Reply to “Comment on ‘Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements' ”

Alice M. Aredes, Pablo L. Saldanha

Seoane et al. [preceding Comment, Phys. Rev. A 111, 066201 (2025)] criticized our work [Phys. Rev. A 109, 022238 (2024)], saying that our argument that realistic interpretations of weak values lead to inconsistencies is not valid for all weak values and quantum theories. This is true. We never intended that the arguments we presented would be valid for all weak values. We believe it is clearly stated in our work that we were dealing only with the weak values related to the quantum paradoxes cited in our paper. Seoane et al. also said in their Comment that the ``general argument'' we present in our paper is formally incorrect. However, this criticism is related to the interpretation they give to the expression ``equivalent,'' which is different from the one we use. In this sense, the presented criticisms are a matter of semantics, not of physics.

Physical Review A•Jun 2, 2025•1 citation

Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements

Alice M. Aredes, Pablo L. Saldanha

Many quantum paradoxes based on a realistic view of weak values were discussed in the last decades. They lead to astonishing conclusions such as the measurement of a spin component of a spin-1/2 particle resulting in $100\ensuremath{\hbar}$, the separation of a photon from its polarization, and the possibility of having three particles in two boxes without any two particles being in the same box, among others. Here, we show that the realistic view of the weak values present in these (and other) works is equivalent to a realistic (and highly controversial) view of quantum measurements, where a measurement reveals the underlying reality of the measured quantity. We discuss that all quantum paradoxes based on weak values simply disappear if we deny these realistic views of quantum measurements and weak values. Our work thus aims to demonstrate the strong assumptions and the corresponding problems present in the interpretation of these quantum paradoxes.

arXiv:2402.09879•Physical Review A•Feb 26, 2024•8 citations

Reply to "Comment on ‘Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements’"

Anonymous

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Comment on "Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements"

Xabier Oianguren-Asua

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Comment on “Association between quantum paradoxes based on weak values and a realistic interpretation of quantum measurements”

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Logical inconsistencies in quantum mechanics

B. E. Y. Svensson

I show that the application of the quantum-mechanical (QM) which-way weak measurement scheme of Vaidman may lead to logical inconsistencies. To this end, I study weak values of projection operators. Weak values are (normalized) amplitudes, operationally defined by a weak measurement followed by postselection. Projector weak values have a direct physical significance. This allows formulating an inconsistency in classical terms, viz., the contradiction in the readings of several measuring devices. To arrive at the contradiction, I also invoke the property of weak measurements not to collapse the wave function but to leave the state of the system unchanged (to lowest order in the weak measurement strength). My arguments rely entirely on basic QM rules plus commonly accepted weak QM measurement approximations. Therefore, the inconsistency challenges QM as such.

arXiv:1803.06162•Mar 16, 2018•0 citations

In their paper (arXiv:2402.09879), Aredes and Saldanha analyze several paradoxes related to weak values and present a "general argument" that aims to show that "realistic interpretations ...of weak values lead to inconsistencies". Although we agree with the identified inconsistencies for the specific weak values analyzed there, in this Comment we demonstrate that the origin of these inconsistencies is not their general argument, which is formally incorrect. We use Bohmian mechanics as a counterexample to confirm that their conclusions are not valid for all weak values and quantum theories. In particular, we show that weak values postselected in position can in fact be interpreted within Bohmian mechanics as properties of quantum systems, detached from any measuring devices, in a consistent and meaningful way.

Seoane et al. [preceding Comment, Phys. Rev. A 111, 066201 (2025)] criticized our work [Phys. Rev. A 109, 022238 (2024)], saying that our argument that realistic interpretations of weak values lead to inconsistencies is not valid for all weak values and quantum theories. This is true. We never intended that the arguments we presented would be valid for all weak values. We believe it is clearly stated in our work that we were dealing only with the weak values related to the quantum paradoxes cited in our paper. Seoane et al. also said in their Comment that the ``general argument'' we present in our paper is formally incorrect. However, this criticism is related to the interpretation they give to the expression ``equivalent,'' which is different from the one we use. In this sense, the presented criticisms are a matter of semantics, not of physics.

Many quantum paradoxes based on a realistic view of weak values were discussed in the last decades. They lead to astonishing conclusions such as the measurement of a spin component of a spin-1/2 particle resulting in $100\ensuremath{\hbar}$, the separation of a photon from its polarization, and the possibility of having three particles in two boxes without any two particles being in the same box, among others. Here, we show that the realistic view of the weak values present in these (and other) works is equivalent to a realistic (and highly controversial) view of quantum measurements, where a measurement reveals the underlying reality of the measured quantity. We discuss that all quantum paradoxes based on weak values simply disappear if we deny these realistic views of quantum measurements and weak values. Our work thus aims to demonstrate the strong assumptions and the corresponding problems present in the interpretation of these quantum paradoxes.

I show that the application of the quantum-mechanical (QM) which-way weak measurement scheme of Vaidman may lead to logical inconsistencies. To this end, I study weak values of projection operators. Weak values are (normalized) amplitudes, operationally defined by a weak measurement followed by postselection. Projector weak values have a direct physical significance. This allows formulating an inconsistency in classical terms, viz., the contradiction in the readings of several measuring devices. To arrive at the contradiction, I also invoke the property of weak measurements not to collapse the wave function but to leave the state of the system unchanged (to lowest order in the weak measurement strength). My arguments rely entirely on basic QM rules plus commonly accepted weak QM measurement approximations. Therefore, the inconsistency challenges QM as such.