Single-photon imaging over 200 km

Long-range active imaging has widespread applications in remote sensing and target recognition. Single-photon light detection ranging (lidar) been shown to have high sensitivity temporal resolution. On the application front, however, operating range of practical single-photon lidar systems is limited about tens kilometers over Earth’s atmosphere, mainly due weak echo signal mixed with background noise. Here, we present a compact coaxial system capable realizing 3D at up 201.5 km. It achieved by using high-efficiency optical devices for collection detection, what believe new noise-suppression technique that efficient long-range applications. We show photon-efficient computational algorithms enable accurate hundreds as few 0.44 photons per pixel. The results represent significant step toward practical, low-power extra-long ranges.