A research team led by Yeom Dong-il, a professor in the departments of physics and energy systems at Ajou University, announced Tuesday that it had successfully developed a fiber-optic quantum entanglement light source in the telecom band based on two-dimensional van der Waals materials, in collaboration with researchers from the Korea Research Institute of Standards and Science (KRISS).
The newly developed fiber-optic quantum light source can connect directly to existing optical communication networks and is expected to serve as a key foundation for next-generation quantum communication, quantum sensing and quantum computing technologies.
Quantum communication and quantum computing use photons as the basic unit for transmitting information. Quantum entanglement — in which two photons share a single quantum state — is particularly critical, as it enables quantum cryptographic communication that is fundamentally immune to hacking, as well as distributed quantum computing capable of managing heat dissipation and error correction.
Conventional quantum entanglement light sources have significant drawbacks: they are bulky, require highly sensitive optical alignment, and suffer large coupling losses when integrated with fiber-optic communication networks. Fiber-based quantum entanglement sources have also been proposed, but they require long fiber lengths and face practical limitations in securing high-quality, noise-free quantum states.
To overcome these challenges, the research team proposed an optical device that directly integrates a van der Waals novel material — SnP₂S₆ — known for its exceptionally strong second-order nonlinear optical properties, onto an optical fiber. The SnP₂S₆ material generates near-infrared nonlinear optical signals even at thicknesses of just a few micrometers (one-thousandth of a millimeter), enabling the team to report for the first time the generation of entangled photon pairs at the standard commercial telecom wavelength of 1,550 nanometers from a fiber-integrated device. The achievement has drawn attention for demonstrating the potential of a next-generation fiber-optic quantum device that connects readily to existing optical networks and operates stably without complex optical alignment.
![A conceptual diagram showing the generation of entangled photon pairs from a 2D material-fiber integrated device. [Provided by Ajou University]](https://wimg.heraldcorp.com/news/cms/2026/08/18/news-p.v1.20260818.ca180e26d27e4254b9fec28432c8a814_P1.png)
The device also demonstrated outstanding results in performance measurements. Its coincidence-to-accidental ratio (CAR) — a metric indicating the purity and quality of generated photons — was 100 times higher than that of existing two-dimensional material-based light sources. Quantum state tomography further verified the formation of high-quality polarization-entangled states, with the generated photons recording a fidelity and purity of up to 0.97, where a value of 1 represents perfect entanglement.
"Research is ongoing to improve device performance so it can be applied to a wide range of real-world systems," Yeom said. "We expect it to find applications across various quantum technology fields, including quantum cryptographic communication, quantum sensing and distributed quantum computing."
Yeom served as corresponding author and Choi Jung-seok of Ajou University as first author on the study. Lee Sang-min, Park Hee-su and Ha Seong-ju of KRISS participated as co-corresponding authors and co-first authors. The research was published online in July in Advanced Science, an international journal covering materials science.
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