Neutral atoms with cavity-assisted interaction for robust long distant quantum communication

We show how to realize long-distance quantum communication using a long-lived quantum memory, which is embedded in a decoherence-free subspace (DFS). Neutral atoms were used in the present scheme, whose interactions are catalyzed by single photons or weak coherent light. The generation, purifcation and swapping of logical entangled states are performed with help of cavity-assisted photon scattering that is robust to random variation in the atom-photon coupling rate, thereby avoiding the requirement for location in the Lamb-Dicke regime. The logical qubits are constructed to be immune to the dominant source of decoherence. Additional errors such as photon losses only cause signalled errors which do not affect the fidelity of the logical entanglement, and are automatically detected in our scheme. With weak coherent light instead of single photons as the input of the cavity, the protocol can also be implemented in the deterministic way because using the homodyne detection instead of single-photon detection, the photon losses only decrease the signal to noise ration but not lead to a failure of operation. It is shown that the idea can be implemented in the context of prominent experimental setups for quantum information processing.