Polarization-Independent Photon Quantum Memorywith Variable Time Delay

A variable time delay photon quantum memory has many applications in quantum computation and communication. For instance, it provides precise synchronization of qubits, highly desirable in a quantum repeater architecture. Here, we are in the process of demonstrating a high-efficiency ``digital'' photon storage system using multiple optical cavities to create variable storage times. These cavities have delay times of 12.5 ns, 125 ns, and 1.25 $\mu $s, with capabilities for multiple photon storage in various degrees of freedom [i.e., polarization, timing, spatial modes, etc.]. The free-space storage cavity system benefits from the availability of low-loss dielectric coatings, in order to attain higher transmission and larger optical bandwidth than current photon quantum memories based on fiber optic loops, atomic vapors, or solid-state media.