RESUMEN
An arbitrary unknown quantum state cannot be measured precisely or replicated perfectly. However, quantum teleportation enables unknown quantum states to be transferred reliably from one object to another over long distances, without physical travelling of the object itself. Long-distance teleportation is a fundamental element of protocols such as large-scale quantum networks and distributed quantum computation. But the distances over which transmission was achieved in previous teleportation experiments, which used optical fibres and terrestrial free-space channels, were limited to about 100 kilometres, owing to the photon loss of these channels. To realize a global-scale 'quantum internet' the range of quantum teleportation needs to be greatly extended. A promising way of doing so involves using satellite platforms and space-based links, which can connect two remote points on Earth with greatly reduced channel loss because most of the propagation path of the photons is in empty space. Here we report quantum teleportation of independent single-photon qubits from a ground observatory to a low-Earth-orbit satellite, through an uplink channel, over distances of up to 1,400 kilometres. To optimize the efficiency of the link and to counter the atmospheric turbulence in the uplink, we use a compact ultra-bright source of entangled photons, a narrow beam divergence and high-bandwidth and high-accuracy acquiring, pointing and tracking. We demonstrate successful quantum teleportation of six input states in mutually unbiased bases with an average fidelity of 0.80 ± 0.01, well above the optimal state-estimation fidelity on a single copy of a qubit (the classical limit). Our demonstration of a ground-to-satellite uplink for reliable and ultra-long-distance quantum teleportation is an essential step towards a global-scale quantum internet.
RESUMEN
Lidar technology is playing an important role in the application of autonomous navigation and hazard avoidance for the landing and cruising exploration on planetary bodies, such as landing on the moon, Mars, and asteroids. We report a Doppler lidar developed for Chang'E-5 mission in this paper. To meet high reliability and resource constraints, time-sharing measuring and in-phase and quadrature processing in this Doppler lidar system was provided and tested. Compared with the traditional linear frequency modulated systems, this lidar system provides excellent detection probabilities of false alarms, especially for the determination of velocity directions. Flight and vibration tests and plume experiments were carried out to further demonstrate the performance and feasibility during the landing mission in late 2020.