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  • User login | JILA-PFC
    Systems Using Light matter Coupling Molecular Coherence and Transformation Exploring high impact synergistic research directions Research Highlights Publications Publications by Year Publications by Title Investigators Education Outreach Partnerships in Informal Science Education in the Community PISEC Education Research Community Outreach News Research Highlights Center News JILA PFC Search form Search Advanced Other JILA Sites JILA Home User login Log in active tab Request new password Username Enter your JILA PFC

    Original URL path: http://jila-pfc.colorado.edu/user (2016-04-29)
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  • A Thousand Splendid Pairs | JILA-PFC
    spaced energy wells created by intersecting laser beams When placed inside the energy wells in the lattice individual ultracold molecules can talk loudly to nearby molecules above and below them as well as to their left and right There s also some weaker communication with molecules farther away The team s recent achievement is to fill enough of these energy wells with cold molecules to establish a working communications network in which every molecule in the lattice must participate With JILA s potassium rubidium KRb molecules enough turns out to be approximately one KRb molecule for every three or four lattice sites At this density the molecules are able to get well connected with each other making it feasible to study their complex interacting network Graduate student Steven Moses and his team from the Jin and Ye collaboration were recently able to create KRb molecules in large enough fraction of the lattice sites to get the molecules well connected Their work was published online in Science on November 6 2015 To make the molecules inside the lattice the researchers had to first place atoms inside the lattice in such a way that many sites contained a single potassium atom and a single rubidium atom Then with a small change in the magnetic field they turned pairs of atoms into KRb molecules However the first step of getting a pair of different atoms into many sites turned out to be the biggest challenge But the cold molecule collaboration met the challenge of getting the potassium and rubidium atoms to like each other well enough to sit side by side on the same site To make them sit peacefully together the researchers had to deal with many issues First potassium and rubidium are very different animals and as different species they like

    Original URL path: http://jila-pfc.colorado.edu/highlights/thousand-splendid-pairs (2016-04-29)
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  • Natural Born Entanglers | JILA-PFC
    technology for the job To prove this the group prepared two ultracold neutral atoms of rubidium then moved them until they were on top of one another This positioning caused the spins of the atoms to become entangled after a bit of time The group then separated the atoms while preserving their entanglement The researchers were able to prove the enduring entanglement via measurements of the spin states of the separated atoms When one of the atoms was spin up the other was always spin down However the direction each spin fluctuated from one experiment to the next This exciting work was reported online in Nature on November 2 2015 The researchers responsible for it included recently minted Ph D Adam Kaufman graduate student Brian Lester research associate Michael Wall Fellows Ana Maria Rey and Cindy Regal and former JILAn Michael Foss Feig of the Joint Quantum Institute One of the most interesting parts of this work was that just moving two almost identical atoms in different spin states on top of one another was sufficient to cause them to become entangled When atoms which exist as waves in the quantum world get this close together their waves overlap As the atom waves talk to each other they discover neither one of them is staying in one of their natural spin states which they are normally happy to remain in indefinitely Both atoms start flipping back and forth between spin up and spin down It s impossible to know which atom is spin up and which one is spin down at any give moment Thus the probability of measuring a particular configuration oscillates in time This process leads to entanglement at certain times All you have to do is place the atoms on top of one another and they evolve

    Original URL path: http://jila-pfc.colorado.edu/highlights/natural-born-entanglers (2016-04-29)
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  • Born of Frustration | JILA-PFC
    to point up or down When mobile electrons collide with impurities their flow that generates a current is distorted similarly to how obstacles distort waves in the sea This process is how ordinary metals acquire resistance However when the impurities are magnetic and have a permanent magnetic moment or spin there is an additional contribution to resistance due to electron collisions accompanied by spin flips This behavior can occur because electrons have their own spin Interactions between two electrons with spin up spin down respectively can cause each one s spin orientation to change or flip to the opposite direction i e to spin down spin up This purely quantum effect profoundly modifies the properties of a metal For instance to an outside observer mobile electrons appear a thousand times heavier than they really are because they tend to spend more time talking to the local spins and hence move slower Naturally the spin flipping collisions of electrons depend on how easily the electrons can modify the state of magnetic impurities If the local spins are rigid and cannot be flipped the system behaves as an ordinary metal An especially interesting situation occurs when this rigidity arises because of competing spin spin interactions with other nearby impurities Whenever these interactions occur the magnet is said to be frustrated because a magnetic impurity does not know if it should allow the mobile electron to flip its spin or if instead it should remain rigid obeying its surrounding localized partners As a result of this confusion the individual spins experience wild quantum fluctuations Clearly magnetic frustration should prevent electrons from efficiently communicating to the local spins hence making them lighter But figuring out which tendency wins remains a puzzle for scientists Interestingly observing ultracold alkaline earth atoms in an optical lattice can

    Original URL path: http://jila-pfc.colorado.edu/highlights/born-frustration (2016-04-29)
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  • The Land of Enhancement: AFM Spectroscopy | JILA-PFC
    are caused by prions The Perkins Group has been continually improving AFM as a powerful tool to understand the structure and function of proteins through force spectroscopy measuring the tiny changes in forces as proteins fold and unfold These folding processes lead to protein function To get better real time force spectroscopy Devin Edwards made a significant breakthrough in optimizing AFM cantilevers for force spectroscopy The cantilever is the diving board like structures that pull on the proteins The first step for Edwards and his colleagues was to start with very small commercially available cantilevers so they would respond quickly to changes in protein structure The key advancement was to substantially reduce the tendency of these small cantilevers to bounce up and down or ring in response to normal random movements of the surrounding liquid molecules known as Brownian motion To do so the team used a focused ion beam microfabrication tool to modify these specialized cantilevers that are simultaneously very small 9 µm long but do not ring However modified cantilevers were initially too curved for use The team then developed an innovative and efficient way to straighten out these diving board like structures and thereby dramatically enhancing the yield of the fabrication process The new AFM system is optimized for single molecule force spectroscopy a technique used to mechanically measure the folding and unfolding of proteins The system is capable of detecting changes in a protein s configuration during the folding or unfolding process because it has an amazing resolution in time of less than 1 µs The researchers responsible for this feat of nanoengineering included research associates Devin Edwards and Robert Walder undergraduate students Jaevyn Faulk and Matthew Bull now a graduate student at Stanford Aric Sanders of NIST Marc Andre LeBlanc and Prof Marcelo Sousa of

    Original URL path: http://jila-pfc.colorado.edu/highlights/land-enhancement-afm-spectroscopy (2016-04-29)
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  • From BEC to Breathing Forever | JILA-PFC
    Einstein The innovative Top Trap was the key to Wieman and Cornell s great achievement Afterwards Cornell Wieman and their colleagues conducted a host of Top Trap experiments publishing 20 significant papers on the physics of ultracold atoms over the next two decades By the end of that 20 year period of discovery however the now much older and more complicated Top Trap was wearing out It was time to think about one last experiment Only one of Cornell s graduate students Dan Lobser knew how to operate the complicated apparatus So Cornell and Lobser enlisted additional help from student assistant Andrew Barentine and Fellow Heather Lewandowski who had previously worked with Lobser Cornell and Lewandowski decided upon a fitting final experiment for the Top Trap a test of a special case of Boltzmann s transport equation that had never been proved This part of Boltzmann s theory predicted that once set in motion a cloud of atoms in a perfectly spherical trap would breathe or oscillate forever It was a perfect experiment for the Top Trap despite being somewhat of an historical oddity Although physicists today revere Boltzmann as a giant in the field of physics he was vehemently attacked when he published the transport equation in 1876 For starters Boltzmann assumed that matter was made of atoms an idea that was vigorously disputed at the time by many scientists who claimed energy was at the root of the physical world With respect to the special case showing that it was possible for a physical process to continue forever without damping or stopping completely everyone knew that was crazy If something starts moving it slows down or cools down Eggs break for heaven s sake and they don t reform into eggs That s just the way the world

    Original URL path: http://jila-pfc.colorado.edu/highlights/bec-breathing-forever (2016-04-29)
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  • The Guiding Light | JILA-PFC
    femtosecond 10 15 s and attosecond 10 18 s x ray bursts to a whole new level The secret to the discovery Research associate Dan Hickstein crossed two visible laser beams that were circularly polarized in opposite directions and sent them through a high harmonic generation HHG process The crossed laser beams entered a gas of argon where the laser field ripped electrons from the noble gas atoms The laser field then changed direction smashing the electrons back into their parent ions and producing an array of harmonics soft x ray beams of different wavelengths The new technique produced different color x ray beams that emerged at distinct angles As a result it was straightforward to isolate and separate beams of different wavelengths and polarizations And with this capability came the power to tailor specific x ray laser beams to individual experiments All the left circularly polarized beams go in one direction and all the right circularly polarized beams go in the other direction said Murnane and Durfee This is quite amazing Nobody thought you could have so much simultaneous control of the direction polarization and spectrum of light in the x ray region The researchers responsible for this breakthrough include Hickstein former senior research associate Franklin Dollar research associates Patrik Grychtol and Ronny Knut former research associate Carlos Hernandez Garcia graduate students Jennifer Ellis Dmitriy Zusin Christian Gentry Tingting Fan and Kevin Dorney Justin Shaw NIST Visiting Fellow Charles Durfee Colorado School of Mines Associate Fellow Agnieszka Jaroń Becker and Fellows Andreas Becker Henry Kapteyn and Margaret Murnane Visible lasers can now be used to precisely control x rays opening the door to investigating materials in ways that were never before possible In fact the technique is so new that no one yet knows its limits The researchers don

    Original URL path: http://jila-pfc.colorado.edu/highlights/guiding-light-0 (2016-04-29)
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  • An Array of Possibilities | JILA-PFC
    an important step toward building larger more complex systems from single atom building blocks His accomplishment opens the door to advances in neutral atom quantum computing investigations of the interplay of spin and motion as well as the synthesis of novel single molecules from different atoms What Lester did was to create a 2 x 2 array of independent optical tweezers traps each containing a single neutral rubidium atom He had to use some interesting physics to get the new system to work because previously anytime two atoms ended up in a single trap during loading they would collide and the energy gained during the collision would knock both atoms out of the trap If enough atoms entered the trap during each loading cycle the loss of pairs would result in a single atom remaining in a trap in about 50 of the loading attempts Then researchers in New Zealand showed that with the right set of experimental conditions the atom atom collisions could be used to preferentially remove just one atom from the trap At JILA Lester and his colleagues adapted these controlled collisions into an efficient and rapid technique to prepare arrays of atoms In the process they discovered precisely how close they could bring the traps together before the multiple traps complicated the process and reduced the efficiency of trap loading Lester s colleagues included Niclas Luick Universität Hamburg newly minted Ph D Adam Kaufman now at Harvard Collin Reynolds Seagate Technologies and Fellow Cindy Regal The change that Lester implemented to his experiment was adding another set of laser beams to the part of the experiment where the atoms are loaded into the traps This set up allowed the researchers to adjust the beams to increase the probability of losing only one atom from each trap

    Original URL path: http://jila-pfc.colorado.edu/highlights/array-possibilities (2016-04-29)
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