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A parallel repetition theorem for entangled projection games

Dinur, Irit and Steurer, David and Vidick, Thomas (2015) A parallel repetition theorem for entangled projection games. Computational Complexity, 24 (2). pp. 201-254. ISSN 1016-3328. doi:10.1007/s00037-015-0098-3.

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We study the behavior of the entangled value of two-player one-round projection games under parallel repetition. We show that for any projection game G of entangled value 1−ϵ<1, the value of the k-fold repetition of G goes to zero as O((1−ϵ^c)^k), for some universal constant c≥1 furthermore the constraint graph of G is expanding, we obtain the optimal c = 1. Previously exponential decay of the entangled value under parallel repetition was only known for the case of XOR and unique games. To prove the theorem, we extend an analytical framework introduced by Dinur and Steurer for the study of the classical value of projection games under parallel repetition. Our proof, as theirs, relies on the introduction of a simple relaxation of the entangled value that is perfectly multiplicative. The main technical component of the proof consists in showing that the relaxed value remains tightly connected to the entangled value, thereby establishing the parallel repetition theorem. More generally, we obtain results on the behavior of the entangled value under products of arbitrary (not necessarily identical) projection games. Relating our relaxed value to the entangled value is done by giving an algorithm for converting a relaxed variant of quantum strategies that we call “vector quantum strategy” to a quantum strategy. The algorithm is considerably simpler in case the bipartite distribution of questions in the game has good expansion properties. When this is not the case, the algorithm relies on a quantum analogue of Holenstein’s correlated sampling lemma which may be of independent interest. Our “quantum correlated sampling lemma” generalizes results of van Dam and Hayden on universal embezzlement to the following approximate scenario: two non-communicating parties, given classical descriptions of bipartite states |ψ⟩,|φ⟩, respectively, such that |ψ⟩≈|φ⟩, are able to locally generate a joint entangled state |Ψ⟩≈|ψ⟩≈|φ⟩ using an initial entangled state that is independent of their inputs.

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Vidick, Thomas0000-0002-6405-365X
Additional Information:© 2015 Springer Basel. Manuscript received 17 June 2014, published online May 19, 2015. We thank Attila Pereszlényi for comments on an earlier version of this manuscript, and the anonymous CCC and Computational Complexity reviewers for useful comments. Irit Dinur’s research was supported by ERC grant No. 239985. Part of the work was done while the author was visiting MIT supported by NSF Contract CCF-1018064, and by Simons Investigator Award of Shafi Goldwasser. Part of David Steurer’s work was done at Microsoft Research New England. Thomas Vidick was partially supported by the Ministry of Education, Singapore, under the Tier 3 grant MOE2012-T3-1-009 and the National Science Foundation under Grant No. 0844626.
Funding AgencyGrant Number
European Research Council (ERC)239985
Simons FoundationUNSPECIFIED
Ministry of Education (Singapore)MOE2012-T3-1-009
Subject Keywords:Parallel repetition; entangled games; projection games; correlated sampling; embezzlement
Issue or Number:2
Record Number:CaltechAUTHORS:20150615-140934465
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58258
Deposited By: Tony Diaz
Deposited On:15 Jun 2015 21:21
Last Modified:10 Nov 2021 22:02

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