2010/08/31 by Tobias Fritz, TOBIAS FRITZ · 142 citations
Computer Science · Mathematics · Physics and Astronomy · #Advanced Operator Algebra Research #Bipartite graph #Commutative property #Conjecture #Hilbert space #Observable #Quantum Information and Cryptography #Quantum Mechanics and Applications #Simple (philosophy) #State (computer science) #Tensor (intrinsic definition) #Tensor product #math-ph #math.MP #math.OA #msc:46L06 #msc:81Q65 #msc:81R15 #quant-ph
paper · pdf · doi:10.1142/s0129055x12500122
published in Reviews in Mathematical Physics 24(05), 1250012 (World Scientific) · 57 pages, to appear in Rev. Math. Phys
arxiv created 2012/05/04 · openalex publication_date 2012/05/24 · arxiv updated 2012/06/04 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
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.