Signaling between time steps prohibits nonlocality beyond hidden nonlocality [article]

Cornelia Spee
2020 arXiv   pre-print
Hidden nonlocality is the phenomenon that entangled states can be local in the standard Bell scenario but display nonlocality after local filtering. However, there exist entangled states which can be described via a local hidden variable model even after local filtering. In this work we show that if signaling between time steps is allowed then these states remain local even when considering the complete statistics of arbitrary sequences and therefore no advantage can be gained by performing
more » ... er sequences in this scenario. We first determine the extreme points of the polytope defined by the no-signaling conditions within the same time step and the arrow-of-time constraints. Based on these results we introduce a notion of locality and provide a complete representation of the corresponding local polytope in terms of inequalities in the simplest scenario. These results imply that in the scenario considered here there is no nonlocality beyond hidden nonlocality. We further propose a device-dependent Schmidt number witness and we compare our finding to known local models in the sequential scenario.
arXiv:2011.12774v1 fatcat:orwzaq7omzdwjhfckaaih2ouxm