Long-distance entanglement distribution using individual atoms in optical cavities

TL;DR

This paper analyzes cavity-based quantum repeater schemes for long-distance entanglement distribution, demonstrating that a heralded CZ-gate scheme achieves high rates and fidelity over 1000 km, outperforming other methods.

Contribution

The study introduces a heralded CZ-gate scheme that enhances long-distance entanglement distribution by mitigating dissipation effects, outperforming previous cavity-based schemes.

Findings

Heralded CZ-gate improves entanglement swapping success probability.

High-fidelity entanglement achieved over 1000 km with realistic parameters.

Scheme outperforms others by up to two orders of magnitude in rate.

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).