{"73754":{"#nid":"73754","#data":{"type":"news","title":"Bose-Einstein Coherence Extends to Condensate Atoms","body":[{"value":"\u003Cp\u003ENew research shows that the unique properties of atomic Bose-Einstein condensates extend to the internal spin states of the atoms from which the condensates are formed.  Bose-Einstein condensates are an unusual form of matter in which all atoms exist in the same quantum state. \u003C\/p\u003E\n\u003Cp\u003EBeyond fundamental physics interest, the work could provide a foundation for future research with potential implications for quantum information systems.\n\u003C\/p\u003E\n\u003Cp\u003EBose-Einstein condensates are formed by cooling gas atoms to a fraction of a degree above absolute zero.  At that temperature, the atoms all drop into the same quantum state.  That makes them coherent, all possessing the same quantum wave function, a state comparable to that of photons in laser systems.\n\u003C\/p\u003E\n\u003Cp\u003EIn a paper published in the November issue of the journal \u003Cem\u003ENature Physics\u003C\/em\u003E, researchers at the Georgia Institute of Technology reported experimental evidence that this coherence also extends to the internal spin degrees of freedom in condensate atoms, which in this case had three different spin states, denoted by 1, 0 and -1.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022The question had been whether the coherence of Bose-Einstein condensates extended to what was going on in the internal states of the atoms,\u0022 explained Michael Chapman, a professor in Georgia Tech\u0027s School of Physics.  \u0022The major message of our work is that it does.  We have seen manifestation that this Bose-Einstein coherence extends to the spin degrees of freedom.  This gives us a much richer system to study.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe research was sponsored by the National Science Foundation and NASA.\n\u003C\/p\u003E\n\u003Cp\u003ECoherence in condensate spin states had been predicted theoretically, and research teams - including Chapman\u0027s - had been seeking experimental confirmation.  While the results have no immediate practical applications, they provide a foundation for future experiments that could ultimately have important real-world uses.\n\u003C\/p\u003E\n\u003Cp\u003EChapman plans to use the experimental system to study how relatively small condensates - those containing between 10 and 100 atoms - interact in a quantum way.  Researchers understand the quantum behavior of small numbers of atoms, while semi-classical physics explains how large atomic ensembles work.  Chapman wants to learn about the behavior of atomic groups in between those two size extremes.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022We are really interested in this regime in which quantum yields to classical,\u0022 he explained.  \u0022The interest is similar to that of nanotechnology because we\u0027re asking the same basic questions.  It\u0027s fundamentally interesting because while we can write down the exact quantum solution for one or a few atoms and the semi-classical approximations for a large group of atoms, we can\u0027t specify what will happen for this in-between region.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EChapman also hopes the small-scale condensate systems will be useful to understanding the atomic analogue of quantum optics or quantum atom optics, where physicists are interested in the behavior of just a few atoms.  In condensates containing a million atoms, adding or removing one atom doesn\u0027t make a difference.  But in groups containing only a hundred or so atoms, theory suggests that adding or removing one atom would make a substantial difference to the properties of the condensate.\n\u003C\/p\u003E\n\u003Cp\u003EChapman notes that internal spin degrees of freedom can exhibit quantum entanglement in a phenomenon known as \u0022spin squeezing.\u0022  Understanding that effect in Bose Einstein condensates could be useful to researchers studying quantum information systems and quantum computing.\n\u003C\/p\u003E\n\u003Cp\u003E\u0022Quantum entanglement is the bread-and-butter of quantum information and quantum computing,\u0022 he said.  \u0022From the first time that people realized you could make a condensate that has spin degrees of freedom, people knew that would be interesting because if it really behaves this way, we could use this entanglement to make systems that might have applications to quantum information.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EExperimentally, Chapman\u0027s research team - which included Ming-Shien Chang and Qishu Qin along with theoretical collaborators Wenxian Zhang and Li You - began with hundreds of millions of atoms of rubidium gas in a magneto-optical atomic trap that was overlapped with an optical trap.  From this large number, they loaded a smaller group of atoms into the optical trap.\n\u003C\/p\u003E\n\u003Cp\u003EBy applying magnetic fields to condensates created in the optical trap, they created condensates in different spin states and chose rubidium atoms with a -1 spin state to begin the experiment.  Into that group, they injected microwave energy, which caused some of the atoms to transition from their original state to a spin 0 state.  They then observed as atoms in the condensate collided with one another.\n\u003C\/p\u003E\n\u003Cp\u003ESome - but not all - collisions produced a change in state among the atoms.  For instance, when two spin -1 atoms collide, their spin orientations remain unchanged because angular momentum must be conserved.  However, when two spin 0 atoms collide, the result can be one spin -1 and one spin +1 atom.  Over time, these collisions created quantities of the third spin state (+1) that did not exist in at the start of the experiment.  \n\u003C\/p\u003E\n\u003Cp\u003E\u0022We created a spin state that didn\u0027t exist in the original form,\u0022 Chapman said.  \u0022That spin state was created by the other spin states that were coherently interactive in the condensate.\u0022\n\u003C\/p\u003E\n\u003Cp\u003EThe researchers periodically turned off the atomic trap and applied a magnetic field gradient that pulled apart the different spin states, allowing measurement of the number of atoms at each spin state.  With that information, the researchers charted spin-state population fluctuations through as many as a dozen oscillations.  \n\u003C\/p\u003E\n\u003Cp\u003EThe dynamics the researchers observed are analogous to Josephson oscillations in weakly connected superconductors and represent a type of matter-wave four-wave mixing.  Beyond the evidence of coherent interaction between the atoms, the research demonstrated the ability to control the evolution of the rubidium system by magnetically applying differential phase shifts to the spin states, Chapman noted.\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EResearch News \u0026amp; Publications Office\u003Cbr \/\u003E\nGeorgia Institute of Technology\u003Cbr \/\u003E\n75 Fifth Street, N.W., Suite 100\u003Cbr \/\u003E\nAtlanta, Georgia  30308  USA\u003C\/strong\u003E\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EMedia Relations Contacts\u003C\/strong\u003E: John Toon (404-894-6986); E-mail: (\u003Ca href=\u0022mailto:john.toon@edi.gatech.edu\u0022\u003Ejohn.toon@edi.gatech.edu\u003C\/a\u003E) or Jane Sanders (404-894-2214); E-mail: (\u003Ca href=\u0022mailto:jane.sanders@edi.gatech.edu\u0022\u003Ejane.sanders@edi.gatech.edu\u003C\/a\u003E).\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003ETechnical Contact\u003C\/strong\u003E: Michael Chapman (404-894-5233); E-mail: (\u003Ca href=\u0022mailto:michael.chapman@physics.gatech.edu\u0022\u003Emichael.chapman@physics.gatech.edu\u003C\/a\u003E)\n\u003C\/p\u003E\n\u003Cp\u003E\u003Cstrong\u003EWriter\u003C\/strong\u003E: John Toon\u003C\/p\u003E","summary":null,"format":"limited_html"}],"field_subtitle":[{"value":"Study finds key property of Bose-Einstein condensates includes spin state of atoms"}],"field_summary":[{"value":"New research shows that the unique properties of atomic Bose-Einstein condensates extend to the internal spin states of the atoms from which the condensates are formed.","format":"limited_html"}],"field_summary_sentence":[{"value":"Research shows new properties for Bose-Einstein"}],"uid":"27303","created_gmt":"2005-11-09 01:00:00","changed_gmt":"2016-10-08 03:03:34","author":"John Toon","boilerplate_text":"","field_publication":"","field_article_url":"","dateline":{"date":"2005-11-09T00:00:00-05:00","iso_date":"2005-11-09T00:00:00-05:00","tz":"America\/New_York"},"extras":[],"hg_media":{"73755":{"id":"73755","type":"image","title":"Population distribution of spin","body":null,"created":"1449178012","gmt_created":"2015-12-03 21:26:52","changed":"1475894678","gmt_changed":"2016-10-08 02:44:38"},"73756":{"id":"73756","type":"image","title":"Population distribution of spin","body":null,"created":"1449178012","gmt_created":"2015-12-03 21:26:52","changed":"1475894678","gmt_changed":"2016-10-08 02:44:38"}},"media_ids":["73755","73756"],"related_links":[{"url":"http:\/\/www.physics.gatech.edu\/ultracool\/","title":"Chapman Research Lab"},{"url":"http:\/\/www.physics.gatech.edu\/people\/faculty\/mchapman.html","title":"Michael Chapman"}],"groups":[{"id":"1188","name":"Research Horizons"}],"categories":[],"keywords":[],"core_research_areas":[],"news_room_topics":[],"event_categories":[],"invited_audience":[],"affiliations":[],"classification":[],"areas_of_expertise":[],"news_and_recent_appearances":[],"phone":[],"contact":[{"value":"\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","format":"limited_html"}],"email":["jtoon@gatech.edu"],"slides":[],"orientation":[],"userdata":""}}}