News from the University of Science and Technology of China (USTC), recently, the LIDAR team led by Prof. Xianghui Xue has made significant progress in the research of quantum LIDAR systems. The team for the first time put forward the theory of wind measurement lidar based on upconversion quantum interference principle, and based on this theoretical innovation successfully developed a prototype. Compared with the traditional coherent wind measurement radar, the new system realizes a dynamic detection range of 0-13km/s speed and a 7-fold improvement in detection sensitivity. This result was published on August 15, 2024 in ACS Photonics.
"Seeing far, seeing fine, measuring fast and measuring accurately" is the goal pursued by LIDAR. Single-photon LIDAR achieves single-photon sensitivity detection compared to conventional LIDAR, which has greatly improved the performance. However, the theory of quantum radar utilizing more quantum precision measurement principles is still in the development stage. Since the discovery of two-photon (HOM) interference in 1987, HOM interference has become a key cornerstone in distinguishing quantum phenomena from classical physics, marking the dawn of a new era of quantum exploration.HOM interference not only plays a fundamental role in precise time measurements and quantum state analysis, but is also central to various applications in quantum information processing. The innovation of quantum precision measurement theory and application based on HOM interference has become a current research hotspot.
Xianghui Xue's group utilizes HOM interference and higher-order quantum erasure to make independent photons from different light sources exhibit quantum interference phenomena, and develops a two-photon interferometric atmospheric lidar system based on upconversion detectors based on this theory. This approach offers single-photon sensitivity, high quantum efficiency, large detection bandwidth, and multi-wavelength applicability. Using quantum erasure combined with an optical compressive sampling method, this quantum radar system is able to record optical signals with a sampling rate of MHz over a bandwidth of 17 GHz (corresponding to 13 km/s), which solves the problem of high sampling rate and large data storage capacity of weak signals in the continuous detection of ultrahigh-speed targets, and paves the way to realize the detection of ultrahigh-speed continuous velocities up to tens of kilometers/second.
More than 17GHz detection bandwidth, frequency detection error ≤ 60MHz (wavelength meter error 60MHz)
In the outfield experiment, the quantum interference radar system uses 70μJ energy to realize wind field detection at a horizontal distance of 16km, which achieves a 7-fold improvement in detection sensitivity with a wind field detection consistency of R2=0.997 compared to the existing LiDAR system.
Wind field detection at 16km distance using 70μJ energy
The core of this technology is to utilize the two-photon interference phenomenon and improve the signal-to-noise ratio by suppressing noise through quantum erasure. Two-photon interference is a quantum optical phenomenon in which two photons interfere with each other and correlations are observed even when they are not present at the same time. Quantum erasure, on the other hand, is a quantum-mechanical process that can be used to eliminate or restore the state of quantum entanglement between two photons by manipulating additional photons.
Telemetry has demonstrated that the technique has great potential for weak signal measurements. Optical frequencies can be detected without the use of a frequency discrimination device, a novel detection method that combines the advantages of direct and coherent detection. The radar system has been fiber-optically integrated and compacted, with potential future applications for continuous remote sensing measurements of ultra-high-speed moving hard and soft targets.
