An arbitrary unknown quantum state cannot be precisely measured or perfectly
replicated. However, quantum teleportation allows faithful transfer of unknown
quantum states from one object to another over long distance, without physical
travelling of the object itself. Long-distance teleportation has been
recognized as a fundamental element in protocols such as large-scale quantum
networks and distributed quantum computation. However, the previous
teleportation experiments between distant locations were limited to a distance
on the order of 100 kilometers, due to photon loss in optical fibres or
terrestrial free-space channels. An outstanding open challenge for a
global-scale "quantum internet" is to significantly extend the range for
teleportation. A promising solution to this problem is exploiting satellite
platform and space-based link, which can conveniently connect two remote points
on the Earth with greatly reduced channel loss because most of the photons'
propagation path is in empty space. Here, we report the first quantum
teleportation of independent single-photon qubits from a ground observatory to
a low Earth orbit satellite - through an up-link channel - with a distance up
to 1400 km. To optimize the link efficiency and overcome the atmospheric
turbulence in the up-link, a series of techniques are developed, including a
compact ultra-bright source of multi-photon entanglement, narrow beam
divergence, high-bandwidth and high-accuracy acquiring, pointing, and tracking
(APT). We demonstrate successful quantum teleportation for six input states in
mutually unbiased bases with an average fidelity of 0.80+/-0.01, well above the
classical limit. This work establishes the first ground-to-satellite up-link
for faithful and ultra-long-distance quantum teleportation, an essential step
toward global-scale quantum internet.Comment: 16 pages, 3 figure
We report the surface exploration by the lunar rover Yutu that landed on the young lava flow in the northeastern part of the Mare Imbrium, which is the largest basin on the nearside of the Moon and is filled with several basalt units estimated to date from 3.5 to 2.0 Ga. The onboard lunar penetrating radar conducted a 114-m-long profile, which measured a thickness of ∼5 m of the lunar regolith layer and detected three underlying basalt units at depths of 195, 215, and 345 m. The radar measurements suggest underestimation of the global lunar regolith thickness by other methods and reveal a vast volume of the last volcano eruption. The in situ spectral reflectance and elemental analysis of the lunar soil at the landing site suggest that the young basalt could be derived from an ilmenite-rich mantle reservoir and then assimilated by 10-20% of the last residual melt of the lunar magma ocean.volcanic history | Imbrium basin | lunar rover Yutu | lunar penetrating radar | Chang'e-3 mission
During the transition period, the extent of corruption in China is higher than before. Meanwhile the forms and characters of Chinese corruption are also different in many important aspects from those of its past and of other countries. This paper explores the causes, consequences of corruption and anti-corruption campaigns of the Chinese government. The major conclusion of this paper is that further political reform toward democracy should be the direction of future anti-corruption efforts.
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