Hybrid quantum repeater with imperfect memories

We discuss the efficiency of quantum error correction (QEC) codes for quantum repeaters based on atomic qubit-entanglement distribution through optical coherent-state communication (hybrid quantum repeater). In particular, we consider nonlocal distributions of two-qubit entangled memory pairs based on unambiguous discrimination measurements of coherent states. The conditionally prepared, entangled states will be subject to local memory dephasing, which is to be suppressed by means of QEC codes. For this realistic case of imperfect memories, we explore the regimes in which the encoding pays off and where it does not. Our model gives the minimum requirements on the local memories, unencoded or encoded,in order to outperform direct transmissions or quantum relay approaches.