Entangling Distant Qubits via Flying Photons Under Thermal Noise Protected by Multi-Time-Bin Encoding

Abstract

Entangling distant stationary qubits—such as superconducting qubits, color centers, trapped ions, and phononic modes—commonly relies on flying photons transmitted through noisy channels. The fidelity of remote entanglement is severely degraded by channel noise. While entanglement purification can theoretically mitigate this effect, its practical implementation in quantum networks is limited by the overhead of local operations and classical communication. We propose a multi-time-bin encoding scheme that improves the fidelity of remote entangled stationary qubits without relying on entanglement purification. Our results show that, compared to single-rail (vacuum–one-photon) encoding, the fidelity in thermal-loss Gaussian channels is improved from 0.66 to 0.89. Taking superconducting qubits connected through microwave-to-optical transduction as a representative implementation, the fidelity is increased from 0.75 to 0.98. Finally, we discuss the prospects for extending the protocol to other stationary-qubit platforms.