243 research outputs found
Multiphoton discrimination at telecom wavelength with charge integration photon detector
We present a charge integration photon detector (CIPD) that enables the
efficient measurement of photon number states at the telecom-fiber wavelengths
with a quantum efficiency of 80% and a resolution less than 0.5 electrons at 1
Hz sampling. The CIPD consists of an InGaAs PIN photodiode and a GaAs JFET in a
charge integration amplifier, which is cooled to 4.2 K to reduce thermal noise
and leakage current. The charge integration amplifier exhibits a low noise
level of 470 nV/Hz1/2. The dark count is as low as 500 electrons/hour.Comment: 4 pages, 4 figures, accepted for Applied Physics letter
Theory of Salt-Water Movement in Iwaki River Mouth
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv
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
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