A research team from the University of Science and Technology of China has introduced a new wind-sensing lidar technology based on up-conversion quantum interference, successfully creating a prototype that marks a significant advancement in the field.
Overview of the quantum erasure HOM (QEHOM) for free-space wind detection. Image Credit: Prof. Xue's team
The goal of lidar technology is to achieve greater range, finer detail, faster measurements, and higher accuracy. Single-photon lidar, which allows for the detection of individual photons, has proven to be a significant leap forward compared to traditional lidar systems. This research builds on these advancements by applying principles of quantum measurement to enhance lidar’s precision.
Since its discovery in 1987, Hong-Ou-Mandel (HOM) interference—also known as two-photon interference—has become a vital tool in precise time measurement, quantum state analysis, and quantum information processing. The application of HOM interference to quantum lidar is a growing area of interest.
The research team developed a theory using HOM interference along with high-order quantum erasure to demonstrate quantum interference with independent photons from different light sources. In HOM interference, two photons create an interference pattern, even when they do not overlap in time, revealing correlations. Quantum erasure involves manipulating additional photons to either eliminate or restore quantum entanglement between two photons.
Building on this theory, the team developed a two-photon interference atmospheric lidar system equipped with an up-conversion detector. The system offers single-photon sensitivity, high quantum efficiency, broad detection bandwidth, and the ability to operate across multiple wavelengths.
In their experiments, the system recorded optical signals at a bandwidth exceeding 17 GHz (corresponding to 13 km/second) at an MHz sampling rate, addressing the challenge of high sampling rates and large data storage requirements when detecting weak signals during continuous monitoring of fast-moving targets.
Field tests showed that the quantum interference lidar system successfully detected wind fields at a distance of 16 km, using only 70 µJ of energy. This represented a sevenfold increase in detection sensitivity compared to conventional lidar systems, with a high level of consistency (R2 = 0.997) in wind field detection.
This successful demonstration of long-distance wind sensing highlights the significant potential of quantum interference lidar in measuring weak signals. It also eliminates the need for frequency discrimination devices by measuring optical frequencies directly, combining the advantages of both direct and coherent detection. Furthermore, the quantum lidar system has been integrated into fiber optics and compacted, making it well-suited for future applications in remote sensing of ultrafast moving targets.
The project was led by Professor Xue Xianghui from the University of Science and Technology of China (USTC), under the Chinese Academy of Sciences (CAS).
Journal Reference:
Wang, C. et. al. (2024) Coherent Two-Photon Atmospheric Lidar Based on Up-Conversion Quantum Erasure. ACS Photonics. doi.org/10.1021/acsphotonics.4c00302