{"61232":{"#nid":"61232","#data":{"type":"news","title":"Quantum Signals Converted to Telecommunications Wavelengths","body":[{"value":"\u003Cp\u003EUsing optically dense, ultra-cold clouds of rubidium atoms, researchers have made advances in three key elements needed for quantum information systems -- including a technique for converting photons carrying quantum data to wavelengths that can be transmitted long distances on optical fiber telecom networks. \u003C\/p\u003E\u003Cp\u003EThe developments move quantum information networks -- which securely encode information by entangling photons and atoms -- closer to a possible prototype system. \u003C\/p\u003E\u003Cp\u003EResearchers at the Georgia Institute of Technology reported the findings Sept. 26 in the journal \u003Cem\u003ENature Physics\u003C\/em\u003E, and in a manuscript submitted for publication in the journal \u003Cem\u003EPhysical Review Letters\u003C\/em\u003E. The research was sponsored by the Air Force Office of Scientific Research, the Office of Naval Research and the National Science Foundation. \u003C\/p\u003E\u003Cp\u003EThe advances include: \u003C\/p\u003E\u003Cp\u003E\u2022 Development of an efficient, low-noise system for converting photons carrying quantum information at infrared wavelengths to longer wavelengths suitable for transmission on conventional telecommunications systems. The researchers have demonstrated that the system, believed to be the first of its kind, maintains the entangled information during conversion to telecom wavelengths -- and back down to the original infrared wavelengths. \u003C\/p\u003E\u003Cp\u003E\u2022 A significant improvement in the length of time that a quantum repeater -- which would be necessary to transmit the information -- can maintain the information in memory. The Georgia Tech team reported memory lasting as long as 0.1 second, 30 times longer than previously reported for systems based on cold neutral atoms and approaching the quantum memory goal of at least one second -- long enough to transmit the information to the next node in the network. \u003C\/p\u003E\u003Cp\u003E\u2022 An efficient, low-noise system able to convert photons of telecom wavelengths back to infrared wavelengths. Such a system would be necessary for detecting entangled photons transmitted by a quantum information system. \u003C\/p\u003E\u003Cp\u003E\u0022This is the first system in which such a long memory time has been integrated with the ability to transmit at telecom wavelengths,\u0022 said Brian Kennedy, a co-author of the \u003Cem\u003ENature Physics \u003C\/em\u003Epaper and a professor in the Georgia Tech School of Physics. \u0022We now have the crucial aspects needed for a quantum repeater.\u0022 \u003C\/p\u003E\u003Cp\u003EThe conversion technique addresses a long-standing issue facing quantum networks: the wavelengths most useful for creating quantum memory aren\u0027t the best for transmitting that information across optical telecommunications networks. Wavelengths of approximately 1.3 microns can be transmitted in optical fiber with the lowest absorption, but the ideal wavelength for storage is 795 nanometers. \u003C\/p\u003E\u003Cp\u003EThe wavelength conversion takes place in a sophisticated system that uses a cloud of rubidium atoms packed closely together in gaseous form to maximize the likelihood of interaction with photons entering the samples. Two separate laser beams excite the rubidium atoms, which are held in a cigar-shaped magneto-optical trap about six millimeters long. The setup creates a four-wave mixing process that changes the wavelength of photons entering it. \u003C\/p\u003E\u003Cp\u003E\u0022One photon of infrared light going in becomes one photon of telecom light going out,\u0022 said Alex Kuzmich, an associate professor in the Georgia Tech School of Physics and another of the \u003Cem\u003ENature Physics\u003C\/em\u003E paper\u0027s co-authors. \u0022To preserve the quantum entanglement, our conversion is done at very high efficiency and with low noise.\u0022 \u003C\/p\u003E\u003Cp\u003EBy changing the shape, size and density of the rubidium cloud, the researchers have been able to boost efficiency as high as 65 percent. \u0022We learned that the efficiency of the system scales up rather quickly with the size of the trap and the number of atoms,\u0022 Kuzmich said. \u0022We spent a lot of time to make a really dense optical sample. That dramatically improved the efficiency and was a big factor in making this work.\u0022 \u003C\/p\u003E\u003Cp\u003EThe four-wave mixing process does not add noise to the signal, which allows the system to maintain the information encoded onto photons by the quantum memory. \u0022There are multiple parameters that affect this process, and we had to work hard to find the optimal set,\u0022 noted Alexander Radnaev, another co-author of the \u003Cem\u003ENature Physics \u003C\/em\u003Epaper. \u003C\/p\u003E\u003Cp\u003EOnce the photons are converted to telecom wavelengths, they move through optical fiber -- and loop back into the magneto-optical trap. They are then converted back to infrared wavelengths for testing to verify that the entanglement has been maintained. That second conversion turns the rubidium cloud into a photon detector that is both efficient and low in noise, Kuzmich said. \u003C\/p\u003E\u003Cp\u003EQuantum memory is created when laser light is directed into a cloud of rubidium atoms confined in an optical lattice. The energy excites the atoms, and the photons scattered from the atoms carry information about that excitation. In the new Georgia Tech system, these photons carrying quantum information are then fed into the wavelength conversion system. \u003C\/p\u003E\u003Cp\u003EThe research team took two different approaches to extending the quantum memory lifetime, both of which sought to mix the two levels of atoms involved in encoding the quantum information. One approach, described in the \u003Cem\u003ENature Physics \u003C\/em\u003Epaper, used an optical lattice and a two-photon process. The second approach, described in the \u003Cem\u003EPhysical Review Letters \u003C\/em\u003Esubmission, used a magnetic field approach pioneered by researchers at the National Institute of Standards and Technology. \u003C\/p\u003E\u003Cp\u003EThe general purpose of quantum networking is to distribute entangled qubits -- two correlated data bits that are either \u00220\u0022 or \u00221\u0022 -- over long distances. The qubits would travel as photons across existing optical networks that are part of the existing global telecommunications system. \u003C\/p\u003E\u003Cp\u003EBecause of loss in the optical fiber that makes up these networks, repeaters must be installed at regular intervals to boost the signals. For carrying qubits, these repeaters will need quantum memory to receive the photonic signal, store it briefly, and then produce another signal that will carry the data to the next node, and on to its final destination. \u003C\/p\u003E\u003Cp\u003E\u0022This is another significant step toward improving quantum information systems based on neutral atoms,\u0022 Kuzmich said. \u0022For quantum repeaters, most of the basic steps have now been made, but achieving the final benchmarks required for an operating system will require intensive optical engineering efforts.\u0022 \u003C\/p\u003E\u003Cp\u003EIn addition to those already mentioned, the research team also included Y.O. Dudin, R. Zhao, H.H. Jen, J.Z. Blumoff and S.D. Jenkins. \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003EGeorgia Institute of Technology\u003Cbr \/\u003E75 Fifth Street, N.W., Suite 314\u003Cbr \/\u003EAtlanta, Georgia 30308 USA\u003C\/strong\u003E \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986)(\u003Ca href=\u0022mailto:jtoon@gatech.edu\u0022\u003Ejtoon@gatech.edu\u003C\/a\u003E) or Abby Vogel Robinson (404-385-3364)(\u003Ca href=\u0022mailto:abby@innovate.gatech.edu\u0022\u003Eabby@innovate.gatech.edu\u003C\/a\u003E). \u003C\/p\u003E\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon \u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":"","field_summary":[{"value":"\u003Cp\u003EUsing ultra-cold clouds of rubidium atoms, researchers have made advances in three key elements needed for quantum information systems -- including a technique for converting photons carrying quantum data to wavelengths that can be transmitted long distances on optical fiber telecom networks.\u003C\/p\u003E","format":"limited_html"}],"field_summary_sentence":[{"value":"Researchers have made key advances in quantum information systems."}],"uid":"27303","created_gmt":"2010-09-26 00:00:00","changed_gmt":"2016-10-08 03:07:27","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2010-09-26T00:00:00-04:00","iso_date":"2010-09-26T00:00:00-04:00","tz":"America\/New_York"},"extras":[],"hg_media":{"61233":{"id":"61233","type":"image","title":"Studying Quantum Information Systems","body":null,"created":"1449176308","gmt_created":"2015-12-03 20:58:28","changed":"1475894533","gmt_changed":"2016-10-08 02:42:13","alt":"Studying Quantum Information Systems","file":{"fid":"191297","name":"tim27740.jpg","image_path":"\/sites\/default\/files\/images\/tim27740_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tim27740_0.jpg","mime":"image\/jpeg","size":1890839,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tim27740_0.jpg?itok=vv41JXP9"}},"61234":{"id":"61234","type":"image","title":"Optical equipment for quantum systems","body":null,"created":"1449176308","gmt_created":"2015-12-03 20:58:28","changed":"1475894533","gmt_changed":"2016-10-08 02:42:13","alt":"Optical equipment for quantum systems","file":{"fid":"191298","name":"toy27740.jpg","image_path":"\/sites\/default\/files\/images\/toy27740_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/toy27740_0.jpg","mime":"image\/jpeg","size":1449159,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/toy27740_0.jpg?itok=Qo7Ylr6h"}},"61235":{"id":"61235","type":"image","title":"Professor Alex Kuzmich in lab","body":null,"created":"1449176322","gmt_created":"2015-12-03 20:58:42","changed":"1475894533","gmt_changed":"2016-10-08 02:42:13","alt":"Professor Alex Kuzmich in lab","file":{"fid":"191299","name":"tdj27740.jpg","image_path":"\/sites\/default\/files\/images\/tdj27740_0.jpg","image_full_path":"http:\/\/tlwarc.hg.gatech.edu\/\/sites\/default\/files\/images\/tdj27740_0.jpg","mime":"image\/jpeg","size":1970194,"path_740":"http:\/\/tlwarc.hg.gatech.edu\/sites\/default\/files\/styles\/740xx_scale\/public\/images\/tdj27740_0.jpg?itok=74kZjLEa"}}},"media_ids":["61233","61234","61235"],"related_links":[{"url":"http:\/\/www.physics.gatech.edu\/","title":"Georgia Tech School of Physics"},{"url":"http:\/\/www.physics.gatech.edu\/people\/faculty\/bkennedy.html","title":"Brian Kennedy"},{"url":"http:\/\/www.physics.gatech.edu\/people\/faculty\/akuzmich.html","title":"Alex Kuzmich"},{"url":"http:\/\/arxiv.org\/abs\/1009.4180","title":"Physical Review Letters paper"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[{"id":"153","name":"Computer Science\/Information Technology and Security"},{"id":"145","name":"Engineering"},{"id":"135","name":"Research"},{"id":"150","name":"Physics and Physical Sciences"}],"keywords":[{"id":"1745","name":"networks"},{"id":"1744","name":"quantum"},{"id":"10747","name":"repeater"},{"id":"2412","name":"telecom"}],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\u003Cp\u003E\u003Cstrong\u003EJohn Toon\u003C\/strong\u003E\u003Cbr \/\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\u003Ca href=\u0022http:\/\/www.gatech.edu\/contact\/index.html?id=jt7\u0022\u003EContact John Toon\u003C\/a\u003E\u003Cbr \/\u003E\u003Cstrong\u003E404-894-6986\u003C\/strong\u003E\u003C\/p\u003E","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}