Pusan National University Builds Hybrid Quantum Network with Identical Photons

Researchers at Pusan National University report demonstrating two-photon interference between a warm cesium atomic ensemble and quantum dots, a critical step toward building scalable quantum networks. The team achieved high spectral overlap, reaching 0.88 between the two sources, and a visibility of 0.65 in their two-photon interference experiments, all without spectral or temporal modifications.

“For the first time, we experimentally demonstrated direct two-photon interference between single photons from two completely independent, physically dissimilar quantum light sources,” explains Professor Han Seb Moon of Pusan National University, detailing how quantum dots functioned as bright photon sources while atomic systems managed storage and synchronization.

Indistinguishable Photon Generation from Cesium and Quantum Dots

A team at Pusan National University has demonstrated a critical advance in hybrid quantum networking by achieving indistinguishable photon generation using both warm cesium atoms and semiconductor quantum dots. This pairing addresses a fundamental challenge in building large-scale quantum communication systems, which demand both reliable quantum memories and efficient single-photon sources. While both technologies have matured independently, integrating them presents significant hurdles, particularly in ensuring the photons emitted from each source behave identically.

The researchers positioned quantum dots to function as bright, high-rate photon sources, while leveraging atomic systems for photon storage and synchronization within this hybrid architecture. This division is central to their approach, as quantum dots are not ideally suited for long-term photon storage, a capability readily provided by atomic ensembles.

A key obstacle to this integration lies in the differing characteristics of light emitted from these sources, requiring precise alignment and synchronization to minimize signal loss. The team overcame this by achieving high spectral overlap, reaching 0.88 nanometers by cooling the system to 12.5 Kelvin, matching the wavelength of the atomic photons at 917 nanometers. This successful demonstration of the Hong-Ou-Mandel effect, a hallmark of indistinguishable photons, is published in Light: Science & Applications on July 15, 2026.

Professor Moon adds, “Our hybrid quantum network bridges the gap between photon generation and storage and provides a global frequency standard for remote quantum emitters.” He envisions this work as a foundation for distributed quantum networks, scalable quantum computers, and ultimately, a functioning quantum internet. This innovative architecture represents a significant step toward realizing practical, large-scale quantum communication infrastructure.