Long-distance entanglement distribution using individual atoms in optical cavities

Abstract: Individual atoms in optical cavities can provide an efficient interface between stationary qubits and flying qubits (photons), which is an essentiel building block for quantum communication. Furthermore, cavity assisted controlled-not (CNOT) gates can be used for swapping entanglement to long distances in a quantum repeater setup. Nonetheless, dissipation introduced by the cavity during the CNOT may increase the experimental difficulty in obtaining long-distance entanglement distribution using these systems. We analyse and compare a number of cavity-based repeater schemes combining various entanglement generation schemes and cavity assisted CNOT gates. We find that a scheme, where high-fidelity entanglement is first generated in a two-photon detection scheme and then swapped to long distances using a recently proposed heralded CZ-gate exhibits superior performance compared to the other schemes. The heralded gate moves the effect of dissipation from the fidelity to the success probability of the gate thereby enabling high-fidelity entanglement swapping. As a result, high-rate entanglement distribution can be achieved over long distances even for low cooperativities of the atom-cavity systems. This high-fidelity repeater is shown to outperform the other cavity-based schemes by up to two orders of magnitude in the rate for realistic parameters and large distances (1000 km).