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2Physics: Transmission of E 2Physics: Transmission of Entangled Photons <br/>over a High-Loss Fr... http://www.2physics.com/2009/05/transmission-of-entangled-photons-... BLOG DURCHSUCHEN.comment-link BLOG MELDEN {margin-left:.6em;}Nächstes Blog» Blog erstellen | Anmelden 2Physics 2Physics Quote: "Without resolving the cosmological singularity a cosmological model will always be incomplete. Standard Big Bang cosmology had to be replaced by a new early universe cosmology because of this problem. The current paradigm, scalar field-driven inflationary cosmology still suffers from this problem and is therefore incomplete." -- Robert Brandenberger (Read his full article: "Cosmology: 5 Needed Breakthroughs" ) 2Physics.com Saturday, May 30, 2009 Reporting ... Transmission of Entangled Photons Key developments in Physics over a High-Loss Free-Space Channel (Email: [email protected] ) Editor: Biplab Bhawal Rupert Ursin << Home Categories [This is an invited article 5 Breakthroughs based on a recently Atomic Physics published work of the authors and their Black Hole collaborators -- Bose-Einstein Condensate 2Physics.com] Condensed Matter Complex System Conferences Cosmology Dark Energy Dark Matter Authors: Alessandro Fedrizzi1, Rupert Ursin1 and Anton Zeilinger1,2, Einstein Affiliation: Elementary Particles 1 Institute for Quantum Optics and Quantum Information (IQOQI), Austria, Gravitation 2 Faculty of Physics, University of Vienna, Austria Gravitational Waves Invisibility Cloak Entanglement is an essential phenomenon of quantum mechanics. Two entangled particles, photons for example, will individually yield random results upon being Laser, Optics measured, but these results will always be perfectly correlated, no matter how far the two Nanotechnology particles are separated from each other. Entanglement has been proven to be at the heart Nobel Prize of a wide range of fundamental quantum effects and it drives exciting practical applications, such as quantum cryptography, quantum teleportation and quantum Physicist computing [1], which would be impossible in a world limited to classical physics. A team Precision Measurement of researchers from the Institute for Quantum Optics and Quantum Information (IQOQI) Quantum Computation in Vienna and the University of Vienna, led by Anton Zeilinger, has now reported the & Communication successful transmission of entangled photon pairs between two Canary Islands, bridging a distance of 144 km and a two-photon attenuation of almost ten million to one. The Squeezed State result, published in Nature Physics [2], is so far the most convincing demonstration to Superstring perform experiments with entangled photons in space. More information on this endeavor can be found at http://www.quantum.at . Read 2Physics.com Past 2Physics articles by members of this collaboration: in your language: "The Frontier of Quantum Communication is the Space" -- Paolo Villoresi, "Entanglement and One-Way Quantum Computing" -- Robert Prevedel and Anton Zeilinger Übersetzung Image 2: Canary islands Gadgets - powered by Google (Google Map). Entangled photons were sent from La Palma to Tenerife (distance 144 km) In their experiment, the researchers exploited a new design of a high-intensity source of entangled photons, which 1 von 3 10.06.2009 13:42 2Physics: Transmission of Entangled Photons <br/>over a High-Loss Fr... http://www.2physics.com/2009/05/transmission-of-entangled-photons-... allowed photon-pair production rates of about one million per second [3]. To Authors This photon source was 2Physics.com publishes located at the Island of La semipopular level articles and Palma, one of the Canary reports on key developments in Islands (see image 2). various fields of Physics. Until From there, both photons the end of 2008, we published of entangled pairs were transmitted through a invited articles only -- but our home-built twin telescope policy has changed. (image 3) and sent to the 144 km distant island of Tenerife, where they were collected by the Optical Ground Station (OGS, image 4), a research observatory operated by the Authors may now submit European Space Agency. This unique location was chosen because of the excellent semipopular articles based on experimental conditions for free-space experiments; clean air, an unobstructed view over their own research paper(s) a very long distance and the availability of a high-tech, large aperture telescope, which published in refereed journals. could be used as a receiver. Alternatively, they may consider Once the primary mirror of the OGS collected the photon pairs, the photons were guided sending a proposal (one short to an experimental chamber by a series of mirrors then split and individually analyzed and paragraph) and a list of related detected. The trickiest part in free-space experiments with single photons is certainly to publications before writing or find the individual photons in the background light. Fortunately, entangled photons are submitting the full article. Our produced at exactly the same time. If therefore two detectors click at exactly the same decision would be conveyed time (in practice within a time window of 1 nanosecond, one billionth of a second), one within a few days after we can be quite sure that the clicks were really produced by two photons of an entangled pair. A series of polarization correlation measurements made it possible to show that the receive the proposal. received photon pairs were still just as highly entangled as when they were produced by the source, with the entanglement quality limited only by background noise. This is astounding as the photons were experiencing a rough ride during their flight time of ½ of a millisecond through the turbulent atmosphere, the longest recorded lifetime for Physics entangled photons so far. Image 3: Thomas Herbst, aligning the homebuilt transmitter telescope at La Palma. Previous proof-of-principle experiments for quantum information in space by the same group and their international collaborators* include the transmission of only one photon of an entangled pair over the same free-space link [4], quantum key distribution with weak coherent pulses [5] and an experiment in which single photons were bounced off a retro-reflecting mirror mounted on a satellite orbiting at an altitude of about 6000 km [6]. The conditions in the new experiment were very close to those expected for a downlink from a satellite to two separate receiver stations on the ground. In particular, the high attenuation (107:1 for photon pairs) the photons were exposed to was similar to that expected in a space scenario. The atmospheric turbulence along the 144 km flight path was in fact much larger, because the atmosphere thins out rapidly at higher altitude and the optical density of the atmosphere along a vertical trajectory into space is equivalent to a merely 7 km long horizontal path through the atmosphere. Moreover, the researchers have shown that observatories like the OGS, which was originally built for classical laser communication and is perfectly suited to track a fast-moving object in orbit, can be adapted for quantum optics experiments. Image 4: Receiver telescope in the optical ground station, Tenerife. Incoming photons are collected by this 1-meter mirror telescope and then guided to the analysis and detection apparatus. Moving entanglement from ground-based laboratories into space will eventually enable experiments on a much larger distance scale than currently possible on ground. A low flying space vessel such as the International Space Station ISS, would be able to transmit photons to ground observers separated by more than 2 von 3 10.06.2009 13:42 2Physics: Transmission of Entangled Photons <br/>over a High-Loss Fr... http://www.2physics.com/2009/05/transmission-of-entangled-photons-... 1000 km. This would benefit tests of the foundations of quantum mechanics as well as practical applications of entangled photons in space, such as long distance quantum cryptography, the secure distribution of keys, which can be used to encrypt messages [7]. Once this initial step into space has been mastered, experiments between two or more moving satellites will allow relativistic tests of quantum mechanics as well as experimental tests on entanglement in gravitational fields [8]. To eventually make this vision a reality, the group in Vienna and their international partners, which include universities, space industry and the European Space Agency, has already started working on a first demonstration prototype of an entangled-photon source that could be integrated into a space-borne terminal. The schedule is compatible with a launch into space within the next decade. This work was supported by the Austrian Research Promotion Agency (FFG) and the European Space Agency (ESA). * In collaboration with LM U Munich and M PQ Garching, Germany, the Univ ersity of Bristol, UK, the University of Padova, Italy and the European Space Agency. References: [1] “The Physics of Quantum Information: Quantum Cryptography, Quantum Teleportation, Quantum Computation”, D. Bouwmeester, A. Ekert and A. Zeilinger (Springer, Berlin, 2001). [2] “High-fidelity transmission of entangled photon pairs over a high-loss free-space channel”, A. Fedrizzi, R. Ursin, T. Herbst, M. Nespoli, R. Prevedel, T. Scheidl, F. Tiefenbacher, T. Jennewein and A. Zeilinger, Nature Physics, doi:10.10138/NPHYS1255 (2009). Abstract. [3] “A wav elength-tunable fibre-coupled source of narrowband entangled photons”, A. Fedrizzi, T. Herbst, A. Poppe, T. Jennewein, T. and A. Zeilinger, Optics Express, 15,
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