Entangled fields in multiple cavities as a testing ground for quantum mechanics

Entangled states provide the necessary tools for conceptual tests of quantum mechanics and other alternative theories. These tests include local hidden variables theories, pre- and post-selective quantum mechanics, QND measurements, complementarity, and tests of mechanics itself against, e.g. the so-called causal communication constraint. We show how to produce nonlocal entangled states of multiple cavity fields. We first discuss two-cavity entanglement, namely the generation of the Bell basis states for this system, when there is at most one photon in either of the cavities. We then discuss a straightforward generalization to similar N-cavity states. These states can be produced by sending appropriately prepared atoms through the cavities. As applications we briefly review a proposal to test quantum mechanics against the causal communication constraint using the two-cavity state and a test of pre- and post-selective quantum mechanics using a three-cavity state and the close connection of the latter to the consistent histories interpretation. Finally we point out the relation between these schemes and the schemes suggested for quantum computing, teleportation and quantum copying.