Steady state entanglement of two coupled qubits

TL;DR

This paper reports on achieving high steady-state entanglement between two coupled qubits using asymmetric incoherent excitation, with potential experimental verification through photon antibunching.

Contribution

It demonstrates that asymmetric excitation configurations optimize steady-state entanglement, surpassing thermal source performance, and explains the underlying purification mechanism.

Findings

Entanglement values three times larger than thermal sources.

Asymmetric excitation configurations are optimal.

Photon antibunching indicates high entanglement.

Abstract

The maximum entanglement between two coupled qubits in the steady state under two independent incoherent sources of excitation is reported. Asymmetric configurations where one qubit is excited while the other one dissipates the excitation are optimal for entanglement, reaching values three times larger than with thermal sources. The reason is the purification of the steady state mixture (that includes a Bell state) thanks to the saturation of the pumped qubit. Photon antibunching between the cross emission of the qubits can be used to experimentally evidence the large degrees of entanglement.