733 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
Fast and User-friendly Quantum Key Distribution
Some guidelines for the comparison of different quantum key distribution
experiments are proposed. An improved 'plug & play' interferometric system
allowing fast key exchange is then introduced. Self-alignment and compensation
of birefringence remain. Original electronics implementing the BB84 protocol
and allowing user-friendly operation is presented. Key creation with 0.1 photon
per pulse at a rate of 486 Hz with a 5.4% QBER - corresponding to a net rate of
210Hz - over a 23 Km installed cable was performed.Comment: 21 pages, 6 figures, added referenc
Twin-photon techniques for fiber measurements
The potential of twin photons generated by parametric down-conversion for
metrological applications are discussed. We present several experimental
results like the measurement of chromatic dispersion and polarization mode
dispersion in optical fibers.Comment: 6 pages, 5 figures, Invited paper for the Symposium on Optical Fiber
Measurements, sponsored by NIST, Boulder, Co, September 15-17, 199
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
Narrowband Photon Pair Source for Quantum Networks
We demonstrate a compact photon pair source based on a periodically poled
lithium niobate nonlinear crystal in a cavity. The cavity parameters are chosen
such that the emitted photon pair modes can be matched in the region of telecom
ultra dense wavelength division multiplexing (U-DWDM) channel spacings. This
approach provides efficient, low-loss, mode selection that is compatible with
standard telecommunication networks. Photons with a coherence time of 8.6 ns
(116 MHz) are produced and their purity is demonstrated. A source brightness of
134 pairs(s.mW.MHz) is reported. The high level of purity and
compatibility with standard telecom networks is of great importance for complex
quantum communication networks
A Fabry-Perot like two-photon interferometer for high-dimensional time-bin entanglement
We generate high-dimensional time-bin entanglement using a mode-locked laser
and analyze it with a 2-photon Fabry-Perot interferometer. The dimension of the
entangled state is limited only by the phase coherence between subsequent
pulses and is practically infinite. In our experiment a pico-second mode-locked
laser at 532 nm pumps a non-linear potassium niobate crystal to produce photon
pairs by spontaneous parametric down-conversion at 810 and 1550 nm.Comment: 9 pages, 9 figure
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