16 research outputs found
Distributing entanglement and single photons through an intra-city, free-space quantum channel
We have distributed entangled photons directly through the atmosphere to a
receiver station 7.8 km away over the city of Vienna, Austria at night.
Detection of one photon from our entangled pairs constitutes a triggered single
photon source from the sender. With no direct time-stable connection, the two
stations found coincidence counts in the detection events by calculating the
cross-correlation of locally-recorded time stamps shared over a public internet
channel. For this experiment, our quantum channel was maintained for a total of
40 minutes during which time a coincidence lock found approximately 60000
coincident detection events. The polarization correlations in those events
yielded a Bell parameter, S=2.27/pm0.019, which violates the CHSH-Bell
inequality by 14 standard deviations. This result is promising for
entanglement-based free-space quantum communication in high-density urban
areas. It is also encouraging for optical quantum communication between ground
stations and satellites since the length of our free-space link exceeds the
atmospheric equivalent.Comment: 8 pages including 1 figure and 2 tables. The first two authors
contributed equally to this wor
Quantum Statistics of Surface Plasmon Polaritons in Metallic Stripe Waveguides
Single surface plasmon polaritons are excited using photons generated via
spontaneous parametric down-conversion. The mean excitation rates, intensity
correlations and Fock state populations are studied. The observed dependence of
the second order coherence in our experiment is consistent with a linear
uncorrelated Markovian environment in the quantum regime. Our results provide
important information about the effect of loss for assessing the potential of
plasmonic waveguides for future nanophotonic circuitry in the quantum regime.Comment: 21 pages, 6 figures, published in Nano Letters, publication date
(web): March 27 (2012
axl has a prognostic role in metastatic colorectal cancer mcrc and is a predictive biomarker of lack of efficacy of chemotherapy ct cetuximab in ras wild type wt patients pts
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Free-Space distribution of entanglement and single photons over 144 km
Quantum Entanglement is the essence of quantum physics and inspires
fundamental questions about the principles of nature. Moreover it is also the
basis for emerging technologies of quantum information processing such as
quantum cryptography, quantum teleportation and quantum computation. Bell's
discovery, that correlations measured on entangled quantum systems are at
variance with a local realistic picture led to a flurry of experiments
confirming the quantum predictions. However, it is still experimentally
undecided whether quantum entanglement can survive global distances, as
predicted by quantum theory. Here we report the violation of the
Clauser-Horne-Shimony-Holt (CHSH) inequality measured by two observers
separated by 144 km between the Canary Islands of La Palma and Tenerife via an
optical free-space link using the Optical Ground Station (OGS) of the European
Space Agency (ESA). Furthermore we used the entangled pairs to generate a
quantum cryptographic key under experimental conditions and constraints
characteristic for a Space-to-ground experiment. The distance in our experiment
exceeds all previous free-space experiments by more than one order of magnitude
and exploits the limit for ground-based free-space communication; significantly
longer distances can only be reached using air- or space-based platforms. The
range achieved thereby demonstrates the feasibility of quantum communication in
space, involving satellites or the International Space Station (ISS).Comment: 10 pages including 2 figures and 1 table, Corrected typo
Free-space quantum key distribution over 144 km
We report on the experimental implementation of a BB84-type quantum key distribution protocol over a 144 km free-space link using weak coherent laser pulses. The security was assured by employing decoy state analysis, and optimization of the link transmission was achieved with bi-directional active telescope tracking. This enabled us to distribute a secure key at a rate of 11 bits/s at an attenuation of about 35 dB. Utilizing a simple transmitter setup and an optical ground station capable of tracking spacecraft in low earth orbit, this outdoor experiment demonstrates the feasibility of global key distribution via satellites