The SURQUID project addressed limitations of current remote sensing technologies by pursuing a multi-scale quantum sensing approach for light detection and ranging (Lidar) with enhanced resolution and sensitivity. Conventional Lidar systems are constrained by shot noise and classical resolution limits, restricting the information that can be extracted from remote targets. SURQUID aimed to overcome these constraints by exploiting non-classical states of light, fast optical modulation, and efficient single-photon detection with picosecond timing and photon-number resolution, establishing a pathway toward quantum-enhanced super-resolution and super-sensitivity.
The project objectives focused on three pillars: (i) realization of quantum light sources for Lidar, (ii) development of a high-performance receiver unit for single-photon counting quantum Lidar, and (iii) demonstration of representative Lidar use cases showcasing improved spatial resolution, material discrimination, and functional sensing. A compact and portable quantum light source prototype was realized, enabling the generation of entangled and non-classical states, including N00N states, spectrally pure pulsed two-mode squeezed vacuum, and non-Gaussian states suitable for remote sensing.
In parallel, SURQUID advanced nanophotonic-integrated SNSPD-based receiver units on silicon platforms combined with high-timing resolution electronics. These receivers achieved ultra-high timing accuracy, enabling millimeter and sub-millimeter ranging resolution, photon-number-resolving capabilities, high-speed electro-optic modulation, and sub-picosecond time tagging. Implemented in compact cryogenic packages, the receiver systems were field-compatible and deployed across diverse Lidar demonstrations, including high-resolution 3D imaging, material classification, time-of-flight and FMCW Lidar, Doppler-based audio reconstruction, defense-relevant target identification, and long-distance ranging using photon bunching in thermal light.
In conclusion, SURQUID demonstrated that integrated quantum state generation, modulation, and single-photon detection enable robust and versatile quantum-enhanced Lidar systems operating beyond classical performance limits, providing a strong foundation for future real-world quantum sensing platforms.
