Toward a Scalable Linear-Cavity Enhanced Warm-Vapor Photonic Quantum Memory.

The coherent storage, buffering and retrieval of photons in a quantum memory enables the scalable creation of photonic entangled states via linear optics and repeat-until success, unlocking applications in quantum communications and photonic quantum computing. Quantum memories based on off-resonant cascaded absorption (ORCA) in atomic vapors allow this storage to be broadband, noise free, and high efficiency. Here, we implement a cavity-enhanced ORCA memory with reduced footprint and reduced power requirements compared to conventional single-pass schemes. By combining a strong magnetic field with polarization control, we maintain a Doppler-free interaction and eliminate the need for optical pumping. Our design establishes the feasibility of large arrays of ultracompact, low-power, near-unit efficiency, noiseless quantum memories running at GHz bandwidth, without the need for atom trapping or cryogenics.