Optical Quantum Memory In Atomic Barium With 880 GHz Bandwidth and 95% Storage Efficiency

We demonstrate quantum memory of single-photon-level coherent pulses of 880 GHz bandwidth with 95.6(3)% storage efficiency in collisionally broadened barium vapor. We measure 26(1)% total efficiency, limited by control field power; 0.49(1) ns memory lifetime, limited by motional dephasing; and a signal-to-noise ratio of ${O}(10^{3})$, limited by two-photon control field scattering. To the best of the authors’ knowledge, this represents the best efficiency, lifetime, and noise performance of atomic quantum memories in the ultrabroadband regime $(\gt100$ GHz bandwidth) to date.