Quantum backflow for many-particle systems

Quantum backflow is the classically-forbidden effect pertaining to the fact that a particle with a positive momentum may exhibit a negative probability current at some space-time point. We investigate how this peculiar phenomenon extends to many-particle systems. We give a general formulation of quantum backflow for systems formed of Nfree nonrelativistic structureless particles, either identical or distinguishable. Restricting our attention...