46. Advanced Quantum Sensing for Astronomy, Quantum Communications, and Other Applications

The aim of this project is to advance research in the field of ultrafast single-photon imaging and its application to quantum-enhanced two-photon interferometry, where photon indistinguishability plays a crucial role. To achieve optimal performance, single photons must be detected with both excellent temporal and spectral resolution—on the order of 10 ps and 10 pm, respectively—with their product approaching the limit set by the Heisenberg Uncertainty Principle [1]. Our research focuses on developing state-of-the-art fast spectrometers capable of enabling this level of performance.
For astronomical applications, the technique relies on interferometric sensing of photon phases from light emitted by two independent astronomical sources observed at two telescope stations separated by a long baseline [2]. It has recently been proposed that these stations would not require a phase-stable optical link if instead they were supplied with quantum-mechanically entangled photon pairs [3]. This approach, in principle, enables arbitrary baselines, achieving angular resolutions on the order of 10 microarcseconds—thus transferring the performance levels seen in radio telescope arrays into the optical domain [4]. Upon successful demonstration, this technology holds great potential to revolutionize astronomical observations.
Beyond astronomy, the fast spectrometers under development have the potential to significantly advance quantum communication networks, particularly because practical entangled-photon sources typically emit across broad spectral bandwidths. A key application is Hong–Ou–Mandel (HOM) interference, which serves as the fundamental mechanism for the entanglement-swapping protocol—an essential process for linking distant quantum nodes, connecting quantum computers, and enabling deviceindependent
quantum key distribution (QKD) [5]. We are exploring how entanglement swapping can be optimized for broadband sources by utilizing multiple spectral bins, thereby substantially improving the efficiency, scalability, and robustness of quantum communication systems. Achieving excellent temporal and spectral resolution is critical for maintaining photon coherence within each temporal and spectral bin, thus enabling high-visibility two-photon interference measurements essential for reliable entanglement swapping protocols.
Additionally, fast imaging sensors with 10 ps-scale resolution will open new possibilities in real-time imaging of chemical and biological reactions and in the detection of photons for a wide range of quantum imaging applications [6–9].