Free-space dissemination of time and frequency with 10 instability over 113 km.

Networks of optical clocks find applications in precise navigation, in efforts to redefine the fundamental unit of the 'second' and in gravitational tests. As the frequency instability for state-of-the-art optical clocks has reached the 10 level, the vision of a global-scale optical network that achieves comparable performances requires the dissemination of time and frequency over a long-distance free-space link with a similar instability of 10. However, previous attempts at free-space dissemination of time and frequency at high precision did not extend beyond dozens of kilometres.

Non-Line-of-Sight Imaging with Picosecond Temporal Resolution.

Non-line-of-sight (NLOS) imaging enables monitoring around corners and is promising for diverse applications. The resolution of transient NLOS imaging is limited to a centimeter scale, mainly by the temporal resolution of the detectors. Here, we construct an up-conversion single-photon detector with a high temporal resolution of ∼1.