Parallel Multi‐Target Detection for Quantum LiDAR

ABSTRACT Quantum LiDAR can offer strong noise resilience in low‐light environments, but most prior demonstrations have relied on raster‐scanned telescope pointing, which interrogates target directions sequentially. Here, we present a wavelength‐randomness–driven beam‐steering scheme that enables parallel multi‐target detection. Using photon pairs generated via spontaneous four‐wave mixing, the probe photon is diffracted by a grating into a wavelength‐dependent angle, which varies from event to event due to intrinsic wavelength randomness. The arrival time of the heralding photon—delayed by propagation through a dispersive medium—encodes the probe wavelength and therefore identifies the corresponding diffraction direction. This time‐to‐angle mapping enables simultaneous interrogation of multiple targets, while the quantum‐correlated measurement yields up to a 1000‐fold signal‐to‐background noise improvement over classical LiDAR under comparable conditions. The corresponding signal‐to‐noise ratio (SNR) enhancement increases with background noise, consistent with theoretical predictions, although it does not exceed unity in the present experiment owing to the limited effective heralding efficiency. Our results establish a laboratory proof‐of‐principle architecture for parallel quantum‐enhanced low‐light sensing based on event‐wise angular encoding and coincidence‐based readout, with potential relevance to quantum metrology and correlated‐photon sensing applications.