A Cavity-Enhanced Room-Temperature Broadband Quantum Memory

Broadband quantum memories hold great promise as multiplexing elements in future photonic quantum information protocols. Alkali vapour Raman memories combine high-bandwidth storage, on-demand read-out, and operation at room temperature without collisional fluorescence noise. However, previous implementations have required large control pulse energies and suffered from four-wave mixing noise. Here we present a Raman memory where the storage interaction is enhanced by a low-finesse birefringent cavity tuned into simultaneous resonance with the signal and control fields, dramatically reducing the energy required to drive the memory. By engineering anti-resonance for the anti-Stokes field, we suppress four-wave mixing and report the lowest unconditional noise floor yet achieved in a Raman-type warm vapour memory.

DOI:http://dx.doi.org/10.1103/PhysRevLett.116.090501