Quantum cloning at the light-atoms interface: copying a coherent light state into two atomic quantum memories

摘要

A scheme for the optimal Gaussian cloning of coherent light states at thelight-atoms interface is proposed. The distinct feature of this proposal isthat the clones are stored in an atomic quantum memory, which is important forapplications in quantum communication. The atomic quantum cloning machinerequires only a single passage of the light pulse through the atomic ensemblesfollowed by the measurement of a light quadrature and an appropriate feedback,which renders the protocol experimentally feasible. An alternative protocol,where one of the clones is carried by the outgoing light pulse, is discussed inconnection with quantum key distribution.