Quantum State Transfer Between Matter And Light

Abstract

Disclosed are apparatus and methods that provide for a coherent quantum state transfer of information from a two-level atomic system (matter) to a single photon (light). Entanglement between a single photon (signal) and a two-component atomic ensemble of cold Rubidium atoms is used to project a quantum memory element (the atomic ensemble) onto any desired state by measuring the signal in a suitable basis. The atomic qubit is read out by stimulating directional emission of a single photon (idler) from the (entangled) collective state of the ensemble. Faithful atomic memory preparation and readout are verified by observed correlations between the signal and idler photons. These results are an important component of distributed quantum networking.