Causal games of work extraction with indefinite causal order

Abstract

An indefinite causal order, where the causes of events are not necessarily in past events, is predicted by the process matrix framework. A fundamental question is how these non-separable causal structures can be related to the thermodynamic phenomena. Here, we approach this problem by considering the existence of two cooperating local Maxwell's demons which try to exploit the presence of global correlations and indefinite causal order to optimize the extraction of work. Thus, we prove that it is possible to have a larger probability to lower the local energy to zero if causal inequalities are violated, and that can be extracted more average work with respect to a definite causal order. However, for non-interacting parties, for the system considered the work extractable cannot be larger than the definite causal order bound.