Heralded atomic-ensemble quantum memory for photon polarization states

Abstract

We describe the mapping of quantum states between single photons and an atomic ensemble.In particular, we demonstrate a heralded quantum memory based on the mapping of a photon polarization state onto a single collective-spin excitation (magnon) shared between two atomic ensembles. The polarization fidelity above 90(2)% for any input polarization far exceeds the classical limit of 2 3 . The process also constitutes a quantum non-destructive probe that detects and regenerates a photon without measuring its polarization.

Cross Modulation of Two Laser Beams at the Individual-Photon Level

“…Our analysis is in good agreement with the experimental results. This method may enable the continuous deterministic entanglement of two light beams for measurements below the standard quantum limit [27,28], the nondestructive detection of individual photons by measuring cavity reflection instead of transmission [22], the imprinting of large photon-photon phase shifts [1,29] by conducting the same experiment away from atomic resonance, and the production of polarization entangled states by extension to another internal state [30,31]. The experimental system [14] is shown in Fig.…”