1,274 research outputs found
Quantum memory for non-stationary light fields based on controlled reversible inhomogeneous broadening
We propose a new method for efficient storage and recall of non-stationary
light fields, e.g. single photon time-bin qubits, in optically dense atomic
ensembles. Our approach to quantum memory is based on controlled, reversible,
inhomogeneous broadening. We briefly discuss experimental realizations of our
proposal.Comment: 4 page
Non-local two-photon correlations using interferometers physically separated by 35 meters
An experimental demonstration of quantum correlations is presented. Energy
and time entangled photons at wavelengths of 704 and 1310 nm are produced by
parametric downconversion in KNbO3 and are sent through optical fibers into a
bulk-optical (704 nm) and an all-fiber Michelson-interferometer (1310 nm),
respectively. The two interferometers are located 35 meters aside from one
another. Using Faraday-mirrors in the fiber-interferometer, all birefringence
effects in the fibers are automatically compensated. We obtained two-photon
fringe visibilities of up to 95 % from which one can project a violation of
Bell's inequality by 8 standard deviations. The good performance and the
auto-aligning feature of Faraday-mirror interferometers show their potential
for a future test of Bell's inequalities in order to examine
quantum-correlations over long distances.Comment: 9 pages including 3 postscript figures, to be published in Europhys.
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Femtosecond Time-Bin Entangled Qubits for Quantum Communication
We create pairs of non-degenerate time-bin entangled photons at telecom
wavelengths with ultra-short pump pulses. Entanglement is shown by performing
Bell kind tests of the Franson type with visibilities of up to 91%. As
time-bin entanglement can easily be protected from decoherence as encountered
in optical fibers, this experiment opens the road for complex quantum
communication protocols over long distances. We also investigate the creation
of more than one photon pair in a laser pulse and present a simple tool to
quantify the probability of such events to happen.Comment: 6 pages, 7 figure
Quantum Cryptography using entangled photons in energy-time Bell states
We present a setup for quantum cryptography based on photon pairs in
energy-time Bell states and show its feasability in a laboratory experiment.
Our scheme combines the advantages of using photon pairs instead of faint laser
pulses and the possibility to preserve energy-time entanglement over long
distances. Moreover, using 4-dimensional energy-time states, no fast random
change of bases is required in our setup : Nature itself decides whether to
measure in the energy or in the time base.Comment: 4 pages including 2 figure
Використання змішаної форми дистанційного навчання на спеціальності "Фізична культура і спорт"
Стаття присвячена актуальній темі, де розглядається використання змішаної форми навчання з застосуванням дистанційного курсу на спеціальності "Фізична культура і спорт"
Lifting Bell inequalities
A Bell inequality defined for a specific experimental configuration can always be extended to a situation involving more observers, measurement settings, or measurement outcomes. In this article, such "liftings" of Bell inequalities are studied. It is shown that if the original inequality defines a facet of the polytope of local joint outcome probabilities then the lifted one also defines a facet of the more complex polytope
Experimental Quantum Teleportation with a 3-Bell-state Analyzer
We present a Bell-state analyzer for time-bin qubits allowing the detection
of three out of four Bell-states with linear optics, two detectors and no
auxiliary photons. The theoretical success rate of this scheme is 50%. A
teleportation experiment was performed to demonstrate its functionality. We
also present a teleportation experiment with a Fidelity larger than the cloning
limit of F=5/6.Comment: 11 pages, 14 figure
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