[论文解读] Quantum LiDAR with Frequency Modulated Continuous Wave

Ming‐Da Huang, Zhan-Feng Jiang+6 more|arXiv (Cornell University)|Jul 21, 2023

Advanced Optical Sensing TechnologiesPhysics and Astronomy被引用 3

一句话总结

本文提出了一种利用马赫-曾德尔干涉仪中纠缠频率调制光子的量子增强频率调制连续波（FMCW）激光雷达系统。通过利用量子纠缠，该系统在不依赖量子脉冲压缩或超出纠缠光子生成的额外非线性过程的前提下，实现了相比经典FMCW激光雷达的$√{n}$量级距离精度提升和$n$倍速度测量分辨率增强。

ABSTRACT

The range and speed of a moving object can be ascertained using the sensing technique known as light detection and ranging (LiDAR). It has recently been suggested that quantum LiDAR, which uses entangled states of light, can enhance the capabilities of LiDAR. Entangled pulsed light is used in prior quantum LiDAR approaches to assess both range and velocity at the same time using the pulses' time of flight and Doppler shift. The entangled pulsed light generation and detection, which are crucial for pulsed quantum LiDAR, are often inefficient. Here, we study a quantum LiDAR that operates on a frequency-modulated continuous wave (FMCW), as opposed to pulses. We first outline the design of the quantum FMCW LiDAR using entangled frequency-modulated photons in a Mach-Zehnder interferometer, and we demonstrate how it can increase accuracy and resolution for range and velocity measurements by $\sqrt{n}$ and $n$, respectively, with $n$ entangled photons. We also demonstrate that quantum FMCW LiDAR may perform simultaneous measurements of the range and velocity without the need for quantum pulsed compression, which is necessary in pulsed quantum LiDAR. Since the generation of entangled photons is the only inefficient nonlinear optical process needed, the quantum FMCW LiDAR is better suited for practical implementations. Additionally, most measurements in the quantum FMCW LiDAR can be carried out electronically by down-converting optical signal to microwave region.

研究动机与目标

• 开发一种实用的量子激光雷达系统，以克服现有脉冲量子激光雷达架构效率低下的问题。
• 通过连续波频率调制与量子纠缠的结合，实现同时、高分辨率的距离与速度测量。
• 减少对纠缠光子生成之外的低效非线性光学过程的依赖，提升系统在芯片集成中的可行性。
• 证明微波下变频处理拍频信号可实现精确的电子测量，从而增强信号处理的鲁棒性。

提出的方法

• 系统采用马赫-曾德尔干涉仪，利用纠缠频率调制光子相干混合参考信号与回波信号。
• 采用三角调频方式生成拍频信号，其频谱分量编码目标的距离与速度信息。
• 推导量子费舍尔信息与Cramér-Rao界，以量化系统的理论精度极限。
• 距离与速度的分辨率由量子拍频信号的离散傅里叶变换（DFT）决定，对应于最大似然估计器。
• 该方案利用时间与路径自由度中的纠缠，以增强灵敏度与分辨率。
• 通过下变频在微波域进行信号处理，实现对多普勒频移的高精度电子测量。

实验结果

研究问题

• RQ1 量子FMCW激光雷达是否能在不使用量子脉冲压缩的情况下实现同时、高分辨率的距离与速度估计？
• RQ2 频率调制光子中的纠缠相较于经典方案，如何提升FMCW激光雷达的精度与分辨率？
• RQ3 系统性能在多大程度上随纠缠光子数$n$而提升？
• RQ4 该系统是否可利用集成光子平台实现，且非线性光学损耗极低？

主要发现

• 与经典FMCW激光雷达相比，该量子FMCW激光雷达实现了$√{n}$量级的距离精度提升和$n$倍的速度分辨率增强。
• 当$n=2$时，与单光子态相比，距离与速度的分辨率均提升了两倍。
• 系统无需量子脉冲压缩即可实现距离与速度的同时测量，解决了脉冲量子激光雷达中的关键瓶颈。
• 唯一低效的非线性过程仅为纠缠光子的生成，与脉冲量子激光雷达相比，显著降低了系统复杂度与损耗。
• 拍频信号的微波下变频处理使得高精度电子测量成为可能，增强了系统稳定性与集成潜力。
• 该架构非常适合在如薄膜铌酸锂等平台实现芯片集成，可实现紧凑、低功耗的量子激光雷达系统。