Theory of two-photon interference in an electromagnetically induced transparency system

We examine the possibility of storing and retrieving a single photon using electromagnetically induced transparency. We consider the theory of a proof-of-principle two-photon interference experiment, in which an atomic vapor cell is placed in one arm of a two-photon interferometer. Since the two-photon state is entangled, we can examine the degree to which entanglement survives. We show that while the experiment might be difficult, it should be possible to perform. We also show that the two-photon interference pattern has oscillatory behavior.