Rosenblum et al. showed recently that a three-level atom in a cavity can function as a perfect “photon turnstile.” Here we explore how this device reshapes the incident pulses, generalize it to the case of an input coherent state, and consider its use in reverse as a “photon adder.” We find that for initially unentangled pulses, adding one photon to an $|n\rangle$ number state is possible with a success probability equal to $1/(n+1)$.

• Received 3 May 2013

DOI:https://doi.org/10.1103/PhysRevA.88.033832