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  • Lattice Light and the Chips | JILA-PFC
    A new robust on chip lattice system which measures 2 3 cm on a side is now commercially available The chip comes with a miniature vacuum system lasers and mounting platform Graduate student Cameron Straatsma and his colleagues recently completed a successful proof of principle experiment with the on chip optical lattice system Their goal was to ensure that the miniature lattice system performs as well as typical laboratory sized systems The researchers included Megan Ivory Janet Duggan former undergraduate student in the Anderson group Jaime Ramirez Serrano and JILA Ph D Evan Salim of ColdQuanta as well as Fellow Dana Anderson In the experiment at JILA the Anderson group created a one dimensional 1D lattice with a laser beam reflected off the chip The lattice was created by pin head sized mirrors directly bonded to atoms on the chip at ColdQuanta As soon as the on chip 1D lattice was ready the investigators placed a tiny Bose Einstein condensate BEC of rubidium atoms in the 1D lattice The BEC was produced right on the chip The researchers soon observed atoms escaping from the on chip 1D lattice via quantum tunneling which is a signal that the miniature lattice was

    Original URL path: http://jila-pfc.colorado.edu/highlights/lattice-light-and-chips (2016-04-29)
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  • Metamorphosis | JILA-PFC
    investigated what happens to potassium atoms that are fermions when they become attracted to each other in an ultracold gas The group included former research associate Yoav Sagi Technion Israel Institute of Technology newly minted Ph D Tara Drake graduate students Rabin Paudel and Roman Chapurin as well as Fellow Deborah Jin In the experiment the researchers found that as they increased the attractions between the potassium atoms fermions atom pairs appeared that acted like bosons The researchers also discovered an intriguing crossover with fermions on one side and bosons on the other side But in the crossover the atoms behaved both like fermions and bosons Since atoms and molecules can either be fermions or bosons the Jin group s goal was to learn more about what happens in the crossover that changes fermions into bosons The bosons and fermions in this experiment were quantum particles with quite different behaviors at ultracold temperatures Independent minded fermions like the potassium atoms in this experiment never occupy the same quantum state because the laws of quantum mechanics don t allow it At zero temperature fermions occupy energy levels in a ladder like fashion with one fermion per energy state In contrast copycat bosons like the pairs of potassium atoms in this experiment can fall into the same low energy state at zero temperature forming a superatom or Bose Einstein condensate The trick to making the Jin group s experiment work was getting the potassium atoms to be strongly attracted to each other which is something potassium atoms don t normally feel Sagi and his colleagues encouraged them by making small changes in the magnetic field around a Feshbach resonance A Feshbach resonance is a special magnetic field strength where small changes have dramatic effects on the interactions of atoms in an ultracold

    Original URL path: http://jila-pfc.colorado.edu/highlights/metamorphosis (2016-04-29)
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  • About Time | JILA-PFC
    deeper understanding the quantum world and providing a novel pathway for investigating unknown phenomena such as dark matter On the flip side the Ye group may have rendered impractical for now the concept of measuring and coordinating absolute time with such a super accurate clock The Ye group s accomplishments mean the global timekeepers will have to pioneer new ways to distribute such precise time and synchronize clocks across the world We are walking through a portal where time itself is changing in response to changes in the shape of the Earth and we used to think of time as a constant explains Travis Nicholson the lead graduate student on the project We were used to thinking the height of a mountain was a constant too All these things turn out to be a little bit fluid if your measurements are sensitive enough The Ye group s new optical atomic clock has this exquisite sensitivity because of a new state of the art stable laser improved measurement techniques and better environmental controls including more precise measurement and control of the temperature of the clock The researchers responsible for the new clock include Nicholson graduate students Sara Campbell and Ross Hutson research associates Edward Marti and Wei Zhang recent JILA Ph D Ben Bloom CU undergraduate student Rees McNally and colleagues from the University of Delaware the National University of Singapore the Joint Quantum Institute and NIST Gaithersburg The new strontium lattice optical atomic clock is so sensitive that it would be affected by gravitational changes due to height differences of as little as 2 cm if researchers moved it up and down in the lab With a clock this sensitive to small changes in gravity the most stable clocks would need to be operated in space far away from variations

    Original URL path: http://jila-pfc.colorado.edu/highlights/about-time (2016-04-29)
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  • A Bug’s Life | JILA-PFC
    some kind of bug they d need to fix But like many unexpected observations in science the bug turned out to be a sign the group had discovered something new and unexpected Benko research associates Linqiang Hua and François Labaye former research associate Tom Allison now Assistant Professor of Physics and Chemistry at Stony Brook University and Fellow Jun Ye decided to figure out exactly what was happening in their experiment They considered whether the bug might have something to do with their new XUV frequency comb laser Frequency comb lasers do not usually have sufficiently powerful pulse peaks to control the behavior of molecules However in this experiment the researchers used an optical cavity to bounce the laser light back and forth multiple times increasing the laser s power With this powerful new precise ruler of light they were not only able to observe the mystery of the moving spectrum but also investigate it The researchers used the powerful laser to send two trains of pulses inside the cavity They observed that the laser field of the first pulse kicked the N 2 O molecules which made the stick shaped molecules line up parallel to each other In other words they became aligned with respect to the laser field As the first laser pulse passed the molecules started to tumble in unison then periodically realigned as time went on The frequency comb laser in the cavity made it possible to align the molecules more than 100 million times per second as compared to 1000 times per second in previous experiments As the molecules were tumbling the researchers aimed a second much more intense pulse at the molecules sometimes when they were aligned and sometimes when they were not Either way the more intense pulse initiated high harmonic generation High

    Original URL path: http://jila-pfc.colorado.edu/highlights/bug%E2%80%99s-life-0 (2016-04-29)
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  • An Ultrafast Photoelectric Adventure | JILA-PFC
    much time it might take for an electron to leave a material such as a helium atom The exciting news at JILA is that the Ultrafast AMO Theory Group has come up with a clever way that may help to answer this question by observing a photoelectron on its way out of but still inside an atom The theorists show how a combination of attosecond 10 18 s and femtosecond 10 15 s laser pulses could be used in the laboratory to follow the electrons inside a helium atom on an ultrafast time scale Such an experiment would open the door to observations of the behavior of electrons inside different atoms and molecules during the photoelectric effect This seminal work appeared in an article published online December 24 2014 in Physical Review Letters The researchers responsible for proposing the use of ultrafast laser pulses to really see something happening inside an atom include recently minted JILA Ph D s Jing Su and Hongcheng Ni as well as Fellows Agnieszka Jaroń Becker and Andreas Becker Their secret was to use a streaking camera in which the variation of the photoelectron s energy with time is measured by the combination of two different laser pulses First one or two photons from the attosecond laser pulse kick the electron out of its ground state inside the atom Then the photoelectron interacts and oscillates in the electric field of the second longer femtosecond laser pulse The femtosecond laser field changes the energy of the electron depending on the time for the photoelectric effect to happen This allows the researchers to probe the electron s behavior inside the atom or molecule during the photoelectric effect For example if an attosecond photon kicks the electron first into resonance with one of the higher energy states in

    Original URL path: http://jila-pfc.colorado.edu/highlights/ultrafast-photoelectric-adventure (2016-04-29)
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  • Terms of Entanglement | JILA-PFC
    Steve Burrows JILA When the Rey theory group first modeled a quantum system at JILA it investigated the interactions of strontium atoms in the Ye group s strontium lattice clock The quantum behavior of these collective interactions was relatively simple to model However the group has now successfully tackled some more complicated systems including the ultracold polar KRb molecule experiment run by the Jin and Ye groups In the process the group has developed a new theory that will open the door to probing quantum spin behavior in real materials atomic molecular and optical gases and other complex systems The new theory promises important insights in different areas of physics quantum information science and biology The new theory comes compliments of research associates Johannes Schachenmayer and Alexander Pikovski as well as Fellow Ana Maria Rey It uses some clever classical techniques to model quantum spin dynamics This capability is important because there is no computer powerful enough to handle a purely quantum description of the spins of particles in complicated systems that are not in equilibrium Remarkably the theory is also able to capture the long range interactions where particles communicate information about the quantum state of their spins even to particles farther away than their nearest neighbors The new approach starts with a mixture of many particles in classical spin up or spin down states This statistical mixture aims to represent intrinsic correlations induced by the long range interactions in a quantum state consisting of superpositions of particles in both possible spin states Superpositions involving many particles are part of what is too complicated about quantum spin dynamics to analyze with today s supercomputers The researchers used a semi classical probability based Monte Carlo method to create a mixture of spin up and spin down particles Over time they

    Original URL path: http://jila-pfc.colorado.edu/highlights/terms-entanglement (2016-04-29)
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  • Mutant Chronicles | JILA-PFC
    JILA Because red fluorescent proteins are important tools for cellular imaging the Jimenez group is working to improve them to further biophysics research The group s quest for a better red fluorescent protein began with a computer simulation of a protein called mCherry that fluoresces red light after laser illumination The simulation identified a floppy i e less stable portion of the protein barrel enclosing the red light emitting compound or chromophore The thought was that when the barrel flopped open it would allow oxygen in to degrade the chromophore thus destroying its ability to fluoresce The group decided that its next step s would be to tweak the natural protein to make it more stable Tweaking proteins is a huge challenge because most combinations of mutations result in a complete loss of the necessary structure to maintain fluorescence Even so the group succeeded in developing a new approach to real world protein improvement that employs a laboratory strategy for directed evolution Directing evolution is challenging The first step requires creating a library of hundreds of thousands of cells containing different mutations of a single protein This step is now relatively easy thanks to the tools of molecular biology The second step requires screening the fluorescence properties of each cell to select only those few that contain top performing mutant proteins To accomplish the selection process the group uses microfluidics combined with several laser beams Its microfluidics system contains micron sized three dimensional transparent channels that carry small streams of liquid and allow cells to flow through them one at a time As the mutant cells pass through the microfluidics channel lasers measure the fluorescent properties of each mutant cell to assess how well the cells maintain their fluorescence when repeatedly excited by the series of laser beams Another laser

    Original URL path: http://jila-pfc.colorado.edu/highlights/mutant-chronicles (2016-04-29)
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  • The Polarized eXpress | JILA-PFC
    to conduct this kind of research in a small university laboratory The JILA team with their collaborators from Oren Cohen s group at Technion in Israel developed a method for creating coherent laser like polarized extreme ultraviolet EUV and soft x rays that are bright enough to investigate how magnetic materials work on the fastest time and smallest length scales This new method is an extension of high harmonic generation HHG In ordinary HHG a strong laser field rips an electron from an atom such as argon or some other noble gas The electrons then smash back into their parent ions twice during the laser optical cycle producing coherent x rays in the process The new approach uses two laser beams with different colors each circularly polarized but in opposite directions With these two beams the electrons are ripped away from the atoms and recombine three times in a cloverleaf pattern More importantly billions of atoms do this all at the same time creating a bright beam of circularly polarized EUV light that can be used for studying the magnetic properties of many important materials On the polarized express as with other HHG research it s like the laser field is the conductor of an orchestra and billions of noble gas atoms are the musicians In the lab the goal is to get as many atomic musicians atoms as there are people on Earth all singing in tune and under the conductor s laser baton If the atoms all play at the same time you get the loudest music brightest beam of EUV light Grychtol and his colleagues figured out how to perform this amazing feat This important work was reported online in Nature Photonics on December 8 2014 The experimentalists responsible for this breakthrough include research associate Patrik Grychtol

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