QKD from a microsatellite: the SOTA experience

The transmission and reception of polarized quantum-limited signals from space is of capital interest for a variety of fundamental-physics experiments and quantum-communication protocols. Specifically, Quantum Key Distribution (QKD) deals with the problem of distributing unconditionally-secure cryptographic keys between two parties. Enabling this technology from space is a critical step for developing a truly-secure global communication network. The National Institute of Information and Communications Technology (NICT, Japan) performed the first successful measurement on the ground of a quantum-limited signal from a satellite in experiments carried out on early August in 2016. The SOTA (Small Optical TrAnsponder) lasercom terminal onboard the LEO satellite SOCRATES (Space Optical Communications Research Advanced Technology Satellite) was utilized for this purpose. Two non-orthogonally polarized signals in the ~800-nm band and modulated at 10 MHz were transmitted by SOTA and received in the single-photon regime by using a 1-m Cassegrain telescope on a ground station located in an urban area of Tokyo (Japan). In these experiments, after compensating the Doppler effect induced by the fast motion of the satellite, a QKD-enabling QBER (Quantum Bit Error Rate) below 5% was measured with estimated key rates in the order of several Kbit/s, proving the feasibility of quantum communications in a real scenario from space for the first time.Comment: 10 pages, 14 figure

A Pilot Study : Which Pairs of Localities Behave Most or Least Alike in England? : a computer\u27s possible contribution to geographical dialectology

The present paper has two purposes. The first is to find which pairs of localities within each selected county in England behave most or least alike with regard to acceptance of the Received Pronunciation (RP) of present British English. The second is to offer a topic for study of regional dialects which cannot be dealt with without the use of a computer. The materials on which we base the present research are those collected according to the procedure described in H. SASAKI (1993). Any pair of localities whith similar speech distribution patterns suggest the possibility that the two localities are more liable to share psychological and physical environments. In contrast to that, any pair of localities with different speech distribution patterns suggest the possibility that the two localities tend to be independent of each other in psychological and physical environments. Thus a computer is expected to provide us with substantial clues for discovering those environments behind distribution patterns of dialect. Hence a computer works as discovery procedure in geographical dialectology