Bell nonlocality with directly generated telecom-band spin-photon entanglement

• URL: http://arxiv.org/abs/2608.08109v1
• Date: Sat, 08 Aug 2026 12:44:50 GMT
• Title: Bell nonlocality with directly generated telecom-band spin-photon entanglement
• Abstract summary: Long-distance distribution of entanglement requires the information carrier to operate in the minimum-loss telecom band of optical fiber.<n>We verify Bell nonlocality by observing a Bell inequality violation of 2.455(77) > 2 using this high-quality entangled pair.<n>This work provides a promising building block for a large-scale atom-based quantum network.
• Score: 2.9677423031379893
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Quantum nonlocality, typically revealed through entanglement distribution across quantum networks, is a cornerstone of quantum information science. Long-distance distribution of entanglement requires the information carrier, i.e. flying photons, to operate in the minimum-loss telecom band of optical fiber. While extensive efforts have been devoted to the direct generation of entanglement between C-band telecom photons and various stationary spins, the verification of quantum nonlocality remains an outstanding challenge. Here, utilizing a dipole transition in rubidium atoms with a wavelength of 1530 nm and a cavity-assisted protocol, we achieve resonant excitation and direct emission of C-band telecom photons from a single atom, generating spin-photon entanglement with a measured Bell state fidelity exceeding 91.4%. We then verify Bell nonlocality by observing a Bell inequality violation of 2.455(77) > 2 using this high-quality entangled pair. These results extend the wavelength of a single-atom quantum emitter to the telecom C-band, achieving sufficiently high-fidelity spin-photon entanglement to finally verify Bell nonlocality. This work thereby provides a promising building block for a large-scale atom-based quantum network capable of distributed quantum metrology and long-distance quantum communication.

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