528 research outputs found
Tunable Up-Conversion Photon Detector
We introduce a simple approach for a tunable up-conversion detector. This
scheme is relevant for both single photon detection or anywhere where low light
levels at telecom wavelengths need to be detected with a high degree of
temporal resolution or where high count rates are desired. A system combining a
periodically poled Lithium niobate waveguide for the nonlinear wavelength
conversion and a low jitter Silicon avalanche photodiode are used in
conjunction with a tunable pump source. We report more than a ten-fold increase
in the detectable bandwidth using this tuning scheme.Comment: 3 pages, 3 figures, Accepted for publication in AP
Long-distance Bell-type tests using energy-time entangled photons
Long-distance Bell-type experiments are presented. The different experimental
challenges and their solutions in order to maintain the strong quantum
correlations between energy-time entangled photons over more than 10 km are
reported and the results analyzed from the point of view of tests of
fundamental physics as well as from the more applied side of quantum
communication, specially quantum key distribution. Tests using more than one
analyzer on each side are also presented.Comment: 22 pages including 7 figures and 5 table
SiPM used as fast Photon-Counting Module and for Multiphoton Detection
We demonstrate fast counting and multiphoton detection abilities of a Silicon
Photo Multiplier (SiPM). In fast counting mode we are able to detect two
consecutive photons separated by only 2.3 ns corresponding to 430 MHz. The
counting efficiency for small optical intensities at a wavelength of 532 nm was
found to be around 8.3% with a dark count rate of 50 kHz at T=-7 degrees
Celsius. Using the SiPM in multiphoton detection mode, we find a good signal
discrimination for different numbers of simultaneous detected photons.Comment: 11 pages, 13 figure
Quantum Key Distribution over 67 km with a plug & play system
We present a fibre-optical quantum key distribution system. It works at
1550nm and is based on the plug & play setup. We tested the stability under
field conditions using aerial and terrestrial cables and performed a key
exchange over 67 km between Geneva and Lausanne.Comment: 8 pages, 3 figures, 2 tables. Submitted to the New Journal of Physic
Energy-time entangled qutrits: Bell tests and quantum communication
We have developed a scheme to generate, control, transmit and measure
entangled photonic qutrits (two photons each of dimension d = 3). A Bell test
of this source has previously been reported elsewhere [1], therefore, here we
focus on how the control of the system is realized. Motivated by these results,
we outline how the scheme can be used for two specific quantum protocols,
namely key distribution and coin tossing and discuss some of their advantages
and disadvantages.Comment: For the conference proceedings of QCMC 200
Heralded photon amplification for quantum communication
Heralded noiseless amplification based on single-photon sources and linear
optics is ideally suited for long-distance quantum communication tasks based on
discrete variables. We experimentally demonstrate such an amplifier, operating
at telecommunication wavelengths. Coherent amplification is performed with a
gain of G=1.98+/-0.2, for a state with a maximum expected gain G=2. We also
demonstrate that there is no need for a stable phase reference between the
initial signal state and the local auxiliary photons used by the amplifier.
These results highlight the potential of heralded quantum amplifiers for
long-distance quantum communication, and bring device-independent quantum key
distribution one step closer.Comment: 5 pages, 4 figure
High efficiency coupling of photon pairs in practice
Multi-photon and quantum communication experiments such as loophole-free Bell
tests and device independent quantum key distribution require entangled photon
sources which display high coupling efficiency. In this paper we put forward a
simple quantum theoretical model which allows the experimenter to design a
source with high pair coupling efficiency. In particular we apply this approach
to a situation where high coupling has not been previously obtained: we
demonstrate a symmetric coupling efficiency of more than 80% in a highly
frequency non-degenerate configuration. Furthermore, we demonstrate this
technique in a broad range of configurations, i.e. in continuous wave and
pulsed pump regimes, and for different nonlinear crystals
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