# USTC physicists observe Bell nonlocality with a single rubidium atom emitting 1530 nm photons

- Published: 2026-11-05 21:26 UTC
- Section: Digital & Computing › Quantum technology
- Tags: Bell nonlocality, spin–photon entanglement, single rubidium atom, telecom C-band photons, 1530 nm, Bell inequality violation, cavity-assisted protocol, quantum networks
- URL: https://realtech.media/news/rt-6b642377a59b3ff65c034b51_ustc_physicists_observe/

**A Hefei team obtained spin–photon entanglement from a single rubidium atom directly in the C-band, the minimum-loss band of optical fiber, and observed a Bell inequality violation.**

![USTC physicists observe Bell nonlocality with a single rubidium atom emitting 1530 nm photons](https://sgzwpqqelzmajkcubgkl.supabase.co/storage/v1/object/public/rt-media/2026/11/f86d3299af5c820e.jpg)
*Hius1, Wikimedia Commons, CC BY 4.0*

A team from the Laboratory of Quantum Information at the University of Science and Technology of China in Hefei generated entanglement between a single rubidium atom and a telecom C-band photon, and used it to verify Bell nonlocality. The result was published in Nature Communications on 4 November 2026. The authors report a measured Bell state fidelity exceeding 91.4% and a Bell inequality violation of 2.455(77) > 2 [1].

## Why the telecom C-band matters

Quantum nonlocality is typically revealed through entanglement distribution across quantum networks and is a cornerstone of quantum information science [1]. Long-distance distribution requires the information carrier, the flying photon, to operate in the minimum-loss telecom band of optical fiber [1].

Extensive efforts have gone into the direct generation of entanglement between C-band telecom photons and various stationary spins. Verification of quantum nonlocality in such systems, however, remained an outstanding challenge, the authors write [1].

## Single-atom experiment

The experiment relies on a dipole transition in rubidium atoms with a wavelength of 1530 nm and a cavity-assisted protocol. With this approach the group achieved resonant excitation and direct emission of C-band telecom photons from a single atom [1].

The emitted photon and the atomic spin formed an entangled pair with a measured Bell state fidelity exceeding 91.4% [1]. Using this pair, the researchers observed a Bell inequality violation of 2.455(77), which exceeds the threshold of 2 [1].

According to the authors, the work extends the wavelength of a single-atom quantum emitter to the telecom C-band and reaches spin–photon entanglement of sufficiently high fidelity to verify Bell nonlocality [1]. This is a laboratory demonstration with a single atom.

The paper has eleven authors. Dong-Yu Huang and Jian Wang contributed equally, and correspondence is addressed to Jian Wang and Chuan-Feng Li. The work involved the Anhui Province Key Laboratory of Quantum Network, the CAS Center for Excellence in Quantum Information and Quantum Physics, and Hefei National Laboratory.

## Sources

1. [Nature Communications](https://doi.org/10.1038/s41467-026-79099-z)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-6b642377a59b3ff65c034b51_ustc_physicists_observe/