Chicago Journal of Theoretical Computer Science

Volume 2016

Article 11

Published by the Department of Computer Science, The University of Chicago.


Parallel repetition and concentration for (sub-)no-signalling games via a flexible constrained de Finetti reduction

Cécilia Lancien
Department de Física: Grup d'Informaciò Quántica
Universitat Autònoma de Barcelona
08193 Bellaterra, Barcelona, Spain
and
Institut Camille Jordan
Université Claude Bernard Lyon 1
Boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France
lancien AT math DOT univ-lyon1 DOT fr

Andreas Winter
Department de Física: Grup d'Informaciò Quántica
Universitat Autònoma de Barcelona
08193 Bellaterra, Barcelona, Spain
and
Insitució Catalana de Recerca i Estudis Avançats
Pg. Lluís Companys, 23, 08010 Barcelona, Spain
andreas.winter AT uab DOT cat

August 18, 2016

Abstract

We use a recently discovered constrained de Finetti reduction (aka “Post-Selection Lemma”) to study the parallel repetition of multi-player non-local games under no-signalling strategies. Since the technique allows us to reduce general strategies to independent plays, we obtain parallel repetition (corresponding to winning all rounds) in the same way as exponential concentration of the probability to win a fraction larger than the value of the game. Our proof technique leads us naturally to a relaxation of no-signalling (NS) strategies, which we dub sub-no-signalling (SNOS). While for two players the two concepts coincide, they differ for three or more players. Our results are most complete and satisfying for arbitrary number of sub-no-signalling players, where we get universal parallel repetition and concentration for any game, while the no-signalling case is obtained as a corollary, but only for games with “full support”.

Submitted August 4, 2015, revised July 18, 2016, and in final form August 16, 2016, published August 18, 2016.

DOI: 10.4086/cjtcs.2016.011


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