Broadband quantum memories for photonic quantum states*

Quantum memories that enable storage and retrieval of photonic quantum states are key components of quantum networks and local quantum information processing schemes. As with any processing task, high bandwidth is favored for scalability, but quantum memories that store GHz-THz bandwidth photonic quantum states have suffered from low efficiency. Experimentally and theoretically determining the optimal system and parameters for broadband quantum storage and retrieval is an ongoing area of research.

One of the most common implementations of photonic quantum memories in ensemble systems such as atomic vapors involves a Lambda-type energy level scheme. The photonic quantum state to be stored is mapped to a long-lived excitation via a two-photon Raman transition mediated by a strong control field. In this context we present our experimentally-motivated theoretical work on optimization of quantum memory efficiency, the sensitivity of the memory efficiency to fluctuations of experimental parameters, and our experimental implementation of a THz-bandwidth quantum memory in hot atomic barium vapor.