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Tsirelson's problem and asymptotically commuting unitary matrices

Narutaka Ozawa

Published Mar 1, 2013• 51 citations
OpenAlex

Abstract

In this paper, we consider quantum correlations of bipartite systems having a slight interaction, and reinterpret Tsirelson's problem (and hence Kirchberg's and Connes's conjectures) in terms of finite-dimensional asymptotically commuting positive operator valued measures. We also consider the systems of asymptotically commuting unitary matrices and formulate the Stronger Kirchberg Conjecture.

Related papers

Tsirelson's problem and asymptotically commuting unitary matrices

Narutaka Ozawa

In this paper, we consider quantum correlations of bipartite systems having a slight interaction, and reinterpret Tsirelson's problem (and hence Kirchberg's and Connes's conjectures) in terms of finite-dimensional asymptotically commuting positive operator valued measures. We also consider the systems of asymptotically commuting unitary matrices and formulate the Stronger Kirchberg Conjecture.

arXiv:1211.2712•Journal of Mathematical Physics•Mar 1, 2013•45 citations

Quantum correlation matrices and Tsirelson’s problem: Previous work and three-player considerations

Gerrit Vos

Tsirelson once claimed that the set of quantum correlations, defined by strategies of non-local two-player games, does not depend on which of two possible models is chosen: the tensor product model or the commuting operator model. He later came back from this claim, and the resulting conjecture is now known as Tsirelson’s problem. The problem has since been proven equivalent to notoriously hard problems in operator theory, such as the Connes’ Embedding Problem and the QWEP conjecture. In this master thesis, we look at the finite dimensional case of Tsirelson’s problem, working out all the details of an existing proof and giving a new, shorter proof which also extends to the nuclear case. Moreover, we give an overview of the equivalence of Tsirelson’s problem and two of Kirchberg’s conjectures, including the QWEP conjecture. Finally, we give some results and considerations for the three-player case of Tsirelson’s problem. The appendix contains proofs of many related results used throughout the thesis, and also a beginner’s introduction to quantum mechanics.

•Jan 1, 2019•0 citations

Tsirelson's problem and Kirchberg's conjecture

Tobias Fritz

This document is an extended abstract of [Fri10b]. See [JNP + 10] for closely related results obtained by different methods. Quantum correlations in composite quantum systems. In the study of quantum entanglement and quantum correlations, one usually assumes that the state space of a composite quantum system is a tensor product HA ⊗ HB, so that the correlations take on the form P (a, b | x, y) = 〈ψ, (A a x ⊗ B b y)ψ〉. (1) with POVM observables Ax a and B y b. However, how is this justified from physical principles? Can we really be sure that this tensor product assumption is appropriate? One possible alternative assumption might be to say that a composite system is defined in terms of a joint Hilbert space H together with, for each site, a set of local observables on H, such that each observable located on the first site commutes with each observable located on the second site; in physical terms, this means that the observables located at different sites are compatible, and can in particular be measured jointly. This is the “commutativity assumption”. In the case of finite-dimensional case, this is effectively equivalent to the

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TSIRELSON'S PROBLEM AND KIRCHBERG'S CONJECTURE

TOBIAS FRITZ

Tsirelson's problem asks whether the set of nonlocal quantum correlations with a tensor product structure for the Hilbert space coincides with the one where only commutativity between observables located at different sites is assumed. Here it is shown that Kirchberg's QWEP conjecture on tensor products of C*-algebras would imply a positive answer to this question for all bipartite scenarios. This remains true also if one considers not only spatial correlations, but also spatiotemporal correlations, where each party is allowed to apply their measurements in temporal succession. We provide an example of a state together with observables such that ordinary spatial correlations are local, while the spatiotemporal correlations reveal nonlocality. Moreover, we find an extended version of Tsirelson's problem which, for each nontrivial Bell scenario, is equivalent to the QWEP conjecture. This extended version can be conveniently formulated in terms of steering the system of a third party. Finally, a comprehensive mathematical appendix offers background material on complete positivity, tensor products of C*-algebras, group C*-algebras, and some simple reformulations of the QWEP conjecture.

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Property (T) and residually finite groups

Gilles Pisier

This is a brief excursion into a topic that belongs to quantum information theory. We prove here that the Connes-Kirchberg problem is equivalent to a question raised by Tsirelson in connection with quantum mechanics. The question involves correlation matrices of various kinds that we discuss using operator valued measures in order to highlight the equivalence of the Tsirelson problem with the LLP of certain free product C*-algebras.

Cambridge University Press eBooks•Feb 10, 2020•0 citations

Unitary induced channels and Tsirelson's problem

Michał Banacki, Paweł Horodecki

Motivated by a recent progress concerning quantum commuting and quantum tensor models of composed systems we investigate a notion of (generalized) unitary induced quantum channel. Using properties of Brown algebras we provide an equivalent characterization of discussed families in both tensor and commuting paradigms. In particular, we provide an equivalent formulation of Tsirelson's conjecture (Connes' embedding problem) in terms of considered paradigms based on protocols which do not require measurements performed on infinite-dimensional subsystems. As a result we show that there is a difference between quantum commuting and quantum tensor models for generalized unitary induced channels.

arXiv:2508.21808•Aug 29, 2025•0 citations
In this paper, we consider quantum correlations of bipartite systems having a slight interaction, and reinterpret Tsirelson's problem (and hence Kirchberg's and Connes's conjectures) in terms of finite-dimensional asymptotically commuting positive operator valued measures. We also consider the systems of asymptotically commuting unitary matrices and formulate the Stronger Kirchberg Conjecture.
Tsirelson once claimed that the set of quantum correlations, defined by strategies of non-local two-player games, does not depend on which of two possible models is chosen: the tensor product model or the commuting operator model. He later came back from this claim, and the resulting conjecture is now known as Tsirelson’s problem. The problem has since been proven equivalent to notoriously hard problems in operator theory, such as the Connes’ Embedding Problem and the QWEP conjecture. In this master thesis, we look at the finite dimensional case of Tsirelson’s problem, working out all the details of an existing proof and giving a new, shorter proof which also extends to the nuclear case. Moreover, we give an overview of the equivalence of Tsirelson’s problem and two of Kirchberg’s conjectures, including the QWEP conjecture. Finally, we give some results and considerations for the three-player case of Tsirelson’s problem. The appendix contains proofs of many related results used throughout the thesis, and also a beginner’s introduction to quantum mechanics.
This document is an extended abstract of [Fri10b]. See [JNP + 10] for closely related results obtained by different methods. Quantum correlations in composite quantum systems. In the study of quantum entanglement and quantum correlations, one usually assumes that the state space of a composite quantum system is a tensor product HA ⊗ HB, so that the correlations take on the form P (a, b | x, y) = 〈ψ, (A a x ⊗ B b y)ψ〉. (1) with POVM observables Ax a and B y b. However, how is this justified from physical principles? Can we really be sure that this tensor product assumption is appropriate? One possible alternative assumption might be to say that a composite system is defined in terms of a joint Hilbert space H together with, for each site, a set of local observables on H, such that each observable located on the first site commutes with each observable located on the second site; in physical terms, this means that the observables located at different sites are compatible, and can in particular be measured jointly. This is the “commutativity assumption”. In the case of finite-dimensional case, this is effectively equivalent to the
Tsirelson's problem asks whether the set of nonlocal quantum correlations with a tensor product structure for the Hilbert space coincides with the one where only commutativity between observables located at different sites is assumed. Here it is shown that Kirchberg's QWEP conjecture on tensor products of C*-algebras would imply a positive answer to this question for all bipartite scenarios. This remains true also if one considers not only spatial correlations, but also spatiotemporal correlations, where each party is allowed to apply their measurements in temporal succession. We provide an example of a state together with observables such that ordinary spatial correlations are local, while the spatiotemporal correlations reveal nonlocality. Moreover, we find an extended version of Tsirelson's problem which, for each nontrivial Bell scenario, is equivalent to the QWEP conjecture. This extended version can be conveniently formulated in terms of steering the system of a third party. Finally, a comprehensive mathematical appendix offers background material on complete positivity, tensor products of C*-algebras, group C*-algebras, and some simple reformulations of the QWEP conjecture.
Motivated by a recent progress concerning quantum commuting and quantum tensor models of composed systems we investigate a notion of (generalized) unitary induced quantum channel. Using properties of Brown algebras we provide an equivalent characterization of discussed families in both tensor and commuting paradigms. In particular, we provide an equivalent formulation of Tsirelson's conjecture (Connes' embedding problem) in terms of considered paradigms based on protocols which do not require measurements performed on infinite-dimensional subsystems. As a result we show that there is a difference between quantum commuting and quantum tensor models for generalized unitary induced channels.