Detecting multipartite spatial entanglement with modular variables

Interference phenomena of quantum systems have been studied in the context of fundamental aspects of quantum physics and are considered a necessary resource for quantum information. Here we investigate the interference of multiparticle wave packets in terms of modular variables, which is a natural and convenient way to describe two or more interfering wave functions. Through the modular-variable description, interesting phenomena appear such as the complementarity between the number of wave packets and the width of the peaks of the momentum distribution. In the multipartite case, this effect produces quantum entanglement. We derive entanglement criteria that test for bipartite entanglement in generic bipartitions of a multipartite quantum state and use these criteria to test for genuine D-partite entanglement.