Chinese team demonstrates 20-km quantum-assisted optical interferometer for future long-baseline telescopes
A team led by Chinese quantum physicist Pan Jianwei has demonstrated a memory-assisted nonlocal optical interferometer with an equivalent baseline of 20 km, marking a major step toward next-generation long-baseline optical telescopes.
The research, titled “Memory-Assisted Nonlocal Interferometer toward Long-Baseline Telescopes” was published on June 17 in the journal Physical Review Letters as an Editors’ Suggestion, highlighting its significance in the field.
The study, conducted by researchers from Hefei National Laboratory and the University of Science and Technology of China, applies cold-atom quantum memories and quantum repeater technologies to large-scale optical interferometry. The experiment demonstrated a nonlocal interferometer with a 20-km equivalent baseline while verifying that quantum memories can compensate for geometric delays that arise during astronomical observations.
The achievement offers a new approach to long-baseline optical interferometric imaging, a technology expected to play an important role in future astronomy.
Astronomers have long relied on interferometry to improve the angular resolution of telescopes by combining light collected at multiple observing sites (Figure 1). While radio telescopes have already formed Earth-sized interferometric arrays, such as the Event Horizon Telescope Collaboration, optical interferometers operating at visible and near-infrared wavelengths have remained limited to baselines of only a few hundred meters because of severe photon transmission losses and the difficulty of compensating rapidly changing geometric delays.
Quantum repeater and quantum networking technologies offer a possible solution. Instead of transmitting fragile starlight directly over long distances, distant telescopes can share entanglement between quantum memories. The starlight collected at each telescope is then interfered locally with photons retrieved from the quantum memories, eliminating transmission losses while allowing the memories to precisely compensate for geometric delays. The approach could make ultra-long-baseline optical interferometry feasible.
Pan’s team has spent years developing the underlying technologies, including long-lifetime, high-efficiency quantum memories and deterministic entanglement based on Rydberg atoms. In 2024, the group built the world’s first metropolitan three-node quantum memory network, followed earlier this year by a demonstration of 100-km device-independent quantum key distribution.
