



01545nas a2200145   4500008004100000245006100041210006100102260001500163300001400178490000700192520113000199100001701329700001601346856003701362       2017                        eng d00aRandomness in nonlocal games between mistrustful players0 aRandomness in nonlocal games between mistrustful players  c2017/06/15  a0595-06100 v173 a<p><span style="font-family: &quot;Lucida Grande&quot;, helvetica, arial, verdana, sans-serif; font-size: 14.4px;">If two quantum players at a nonlocal game G achieve a superclassical score, then their measurement outcomes must be at least partially random from the perspective of any third player. This is the basis for device-independent quantum cryptography. In this paper we address a related question: does a superclassical score at G guarantee that one player has created randomness from the perspective of the other player? We show that for complete-support games, the answer is yes: even if the second player is given the first player&#39;s input at the conclusion of the game, he cannot perfectly recover her output. Thus some amount of local randomness (i.e., randomness possessed by only one player) is always obtained when randomness is certified from nonlocal games with quantum strategies. This is in contrast to non-signaling game strategies, which may produce global randomness without any local randomness. We discuss potential implications for cryptographic protocols between mistrustful parties.</span></p>1 aMiller, Carl1 aShi, Yaoyun  uhttps://arxiv.org/abs/1706.04984