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  • The Fickle Finger of Fate | JILA-PFC
    Baxley and Ryan Wilson JILA Chris Ticknor LANL Putting the brakes on a superfluid dipolar Bose Einstein condensate BEC just got a whole lot more interesting Last year the Bohn theory group explored what would occur in a dipolar BEC when a laser probe think of it like a finger tickled a BEC just hard enough to excite a roton see JILA Light Matter Summer 2010 The roton is a strange type of quasi particleformed when a number of strongly magnetic atoms or dipolar molecules come together and act like a different kind of particle It is like a sound wave with regions of high and low density However the relationship between its wavelength and frequency is decidedly strange When a roton s wavelength gets small enough its frequency stops growing in fact it gets smaller The onset of this oddball phenomenon determines the appearance of ripples that are associated with the drag on a laser probe or finger as it traverses a dipolar BEC But that s not all that can happen according to a new study by former JILA graduate student Chris Ticknor now at Los Alamos National Laboratory graduate student Ryan Wilson and Fellow John Bohn A sufficiently wide laser can also create vortices in the BEC which are a lot easier to see in an experiment than a roton There are other interesting experimental implications in the new study This work considers superfluid dipolar chromium atoms in a pancake shaped trap created by two pairs of intersecting laser beams This trap forces the dipolar atoms to line up side by side and now they repel one another The atoms can however be tilted slightly in one direction and this makes all the difference Under these circumstances the rotons can be fickle when they re tickled A

    Original URL path: http://jila-pfc.colorado.edu/highlights/fickle-finger-fate (2016-04-29)
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  • Strontium Clock Performance Skyrockets | JILA-PFC
    the atoms no longer being identical And once they were distinguishable formerly unneighborly atoms were able to run into each other compromising clock performance See JILA Light Matter Spring 2009 Ever since this discovery the Ye group has been looking for strategies to reduce the number of atom atom collisions and the resulting frequency shifts Now thanks to help from theorist Ana Maria Rey the group has solved the problem of colliding fermions In solving the problem a team led by research associate Matt Swallows reduced the inaccuracy of the optical atomic clock arising from atomic collisions by 50 fold reaching the level of 1 x 10 17 This result has eliminated the need for compromise between precision and accuracy in the on going development of the group s Sr lattice clock which uses many quantum particles In addition to Swallows Rey and Ye the clock team included graduate students Michael Martin Michael Bishof and Sebastian Blatt as well as a visiting scientist Yige Lin The team was presented with a JILA Scientific Award in August of 2010 for their accomplishment Their breakthrough research was published online in Science Express on February 3 To stop the fermions from colliding the team used a new two dimensional trap design that ensures strong interactions among the atoms Paradoxically strong interactions actually suppress collisions among the Sr atoms Here s how When Sr atoms are first loaded into the clock s optical traps they are identical and cannot collide However when the Sr atoms interact with the clock laser some of them enter slightly different states and become distinguishable Once they re distinguishable they can collide In the old pancake trap the atoms interacted weakly and had no trouble jumping back and forth between identical and distinguishable states However when atomic interactions get

    Original URL path: http://jila-pfc.colorado.edu/highlights/strontium-clock-performance-skyrockets (2016-04-29)
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  • The Quantum Modeling Agency | JILA-PFC
    Ye explains You can assemble precisely controlled atoms or molecules to mimic complex materials add in well defined interactions between particles and then watch the system dynamics unravel themselves For example the state of the matter might jump from one configuration to another simply because of quantum fluctuations Ye will soon get a chance to try his hand at building a quantum simulator thanks to Fellow Ana Maria Rey and her theorist colleagues from the University of Colorado Harvard the Joint Quantum Institute the Harvard Smithsonian Center for Astrophysics and the University of Innsbruck Rey and her colleagues have come up with a perfect simulator of condensed matter systems made from ultracold alkaline earth atoms One such atom strontium 87 Sr is already famous for its roles in the Ye group s creation of a high accuracy optical atomic clock Alkaline earth atoms may also one day play a role in quantum information processing See JILA Light Matter Spring 2009 When alkaline earth atoms are loaded in optical lattices egg carton shaped energy wells formed by interacting laser beams they can be used as quantum simulators of many body phenomena according to Rey and her colleagues They have shown that one of the features of alkaline earth atoms is particularly important for creating quantum simulators the nuclear spins of alkaline earth atoms are almost completely decoupled from the two valence electrons under carefully selected conditions This decoupling means that the atoms can be used to create relatively large systems with an unprecedented degree of symmetry This symmetry prevents spin changing collisions between the atoms something that is very attractive for a laboratory quantum simulator The proposed quantum simulator would allow researchers to study 87 Sr atoms simultaneously in the ground state and in a stable optically excited state The atoms would be placed in different optical lattices according to their electronic states the lattice filled with ground state atoms could be moved relative to the stationary lattice containing the optically excited atoms Each lattice could have atoms with different nuclear spins however The nuclear spins would control how the atoms interact with each other The two optical lattices could be prepared either deeper or shallower as compared to one another This controllability would make it possible to create atomic analogs of condensed matter systems exhibiting nontrivial interplay between spin electronic orbitals and charge The ground and excited states in the atomic system will play the role of the electronic orbitals and the nuclear spin will play the role of the electronic spin The mass of the atoms will be the analog of the electron charge because when atoms move they create a mass current Like electrical current mass transport can be measured The new quantum simulator promises to open the door to understanding the physics of some very exotic materials including 1 heavy fermion materials in which spin interactions between a cloud of conduction electrons and a band of localized spins causes the conduction electrons to behave as if they

    Original URL path: http://jila-pfc.colorado.edu/highlights/quantum-modeling-agency (2016-04-29)
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  • Sharing the Adventure of Science | JILA-PFC
    classes to elementary and middle school students in the St Vrain School District The volunteers expect to stimulate the children to learn to think critically enjoy science activities and become confident in their own abilities to master difficult concepts What they may not anticipate at first is that they will learn some important skills themselves including the ability to communicate scientific concepts in everyday language and with that new ability gain a better understanding of education The program that brings young scientists from JILA together with the St Vrain students is called Partnerships for Informal Science Education in the Community PISEC The after school science program is part of the JILA NSF Physics Frontier Center PFC It s the brainchild of the PFC s Outreach PISEC Program Director Dr Laurel Mayhew who is collaborating with CU s Physics Education Research group on developing the program In 2009 Mayhew and Noah Finkelstein a CU physics professor used the Communication in Everyday Language Assessment to evaluate improvement in the ability of PISEC instructors to communicate science concepts in everyday language The assessment included two videotaped sessions of each of nine instructors the first before the instructors had any teaching experience with children and the second after a semester of regular science lessons In both the pre and post videotaped presentations the participants were told to imagine they were teaching a lesson to a group of children 11 14 years old In the first set of videotapes most study participants stood in one place used few gestures failed to connect the concepts they were explaining to children s lives and used complex scientific terms to describe the concepts of motion speed and velocity However the ability of most participants to explain motion related concepts improved significantly by the end of the semester The

    Original URL path: http://jila-pfc.colorado.edu/highlights/sharing-adventure-science (2016-04-29)
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  • Rainbows of Soft X-Rays | JILA-PFC
    thanks to Tenio Popmintchev Ming Chang Chen and their colleagues in the Kapteyn Murnane group By focusing a femtosecond laser into a gas Popmintchev and Chen generated many colors of x rays at once in a band that stretched from the extreme ultraviolet into the soft x ray region of the electromagnetic spectrum spanning wavelengths of ranging from about 6 to 2 5 nm This broad x ray band has so many different colors that all the waves can be added together to form the shortest strobe light in existence This light may be as short as 10 attoseconds or 10 quintillionths of a second 10 17 s Proof of the laserlike nature of the soft x ray beams was featured on the cover of the October 22 2010 issue of Physical Review Letters The new rainbow of x rays spans the water window region of the spectrum where biological molecules rich in carbon hydrogen and nitrogen can be clearly imaged without being obscured by absorption due to water Researchers can use this new technology to probe the internal structures of cells or nanostructures with x rays produced by a tabletop setup The new x ray laser is in essence a coherent version of the Roentgen x ray tube Remarkably the Kapteyn Murnane group accomplished more than just opening up the water window region to tabletop laser x rays Popmintchev has already predicted that by using longer driving laser wavelengths high harmonic generation HHG can reach the hard x ray region of the spectrum HHG was described Exotic Probes in the Spring 2008 issue of JILA Light Matter http jila colorado edu content exotic probes And incredibly the even broader x ray rainbows that will be generated there have the potential to produce zeptosecond 10 21 s laser pulses The

    Original URL path: http://jila-pfc.colorado.edu/highlights/rainbows-soft-x-rays (2016-04-29)
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  • Sayonara Demolition Man | JILA-PFC
    mechanical phase of each atom before they are probed If all this sounds hard that s because it is However Fellow James Thompson and graduate students Zilong Chen Justin Bohnet Shannon Shankar and Jiayan Dai recently succeeded in making a precision coherence preserving quantum nondemolition measurement of a million cold rubidium 87 Rb atoms inside an optical cavity If we were trying to investigate Schrödinger s cat which exists inside a box in a superposition between being alive and being dead Thompson says We d be trying not to open the box while we were figuring out what s in there What we do with our atom ensembles is like putting lots of cats in one box and counting the yowls We can tell how many cats are still alive but not which cats The Thompson s group s yowls are all the signals from the energy levels of the 87 Rb atoms Its box is an optical cavity that uses an optical lattice to keep the 87 Rb atoms well localized between two mirrors There the atoms interact or talk to the cavity resonances This quantum conversation causes the cavity resonance to split into two a phenomenon physicists call a vacuum Rabi splitting The size of the frequency difference between the two resonances depends directly on the number of atoms in a spin up state With their setup the researchers can accurately and precisely count the total number of atoms in spin up and spin down states by scanning a laser across the two resonances But they aren t counting individual atoms and they have no way of telling which atoms are in a particular spin state Coherence is preserved only to the extent that the atoms talk to the universe via the cavity mode Atoms love to talk

    Original URL path: http://jila-pfc.colorado.edu/highlights/sayonara-demolition-man (2016-04-29)
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  • Deciphering Nature's Fingerprints | JILA-PFC
    technique can now identify traces of a wider variety of molecules found in mixtures of gases It offers many advantages for chemical analysis of the atmosphere climate science studies and the detection of suspicious substances In addition planning is already underway for clinical trials of a noninvasive medical breath analyzer that incorporates technique See JILA Light Matter Spring 2008 The new trace gas detection system was developed by former research associate Florian Adler who worked with research associates Piotr Maslowski and Aleksandra Foltynowicz graduate students Kevin Cossell and Travis Briles Fellow Jun Ye and a colleague from IMRA American Inc With the new mid IR frequency comb as a source of light the range of the molecular fingerprinting technique has been extended into spectral regions that cover frequencies associated with fundamental vibrations of many organic molecules containing carbon and hydrogen atoms As a result the technique can now identify more molecules and at lower concentrations The comb is generated by an ultrafast laser that emits tens of thousands of different colors of light of specific frequencies that can be precisely measured When comb light passes through a mixture of gases different chemicals absorb different colors of the light By analyzing which colors are absorbed and in what amounts the researchers can determine the identity and concentration of the different molecules in a mixture In a test of the new system Adler and his colleagues measured the spectra of a dozen organic molecules including the greenhouse gases methane carbon dioxide and nitrous oxide air pollutants isoprene and formaldehyde and two molecules probed in human breath analysis ethane a sign of asthma and methanol an indicator of kidney failure The new laser uses an optical parametric oscillator or OPO to shift the light from a near IR frequency comb to the mid

    Original URL path: http://jila-pfc.colorado.edu/highlights/deciphering-natures-fingerprints (2016-04-29)
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  • The Guiding Light | JILA-PFC
    possible to align the microscope tip and sample with a precision of 40 nm before the AFM tip even touches the sample The researchers say that the new sample detection scheme solves the needle in a haystack problem of nanoscale microscopy Until now scientists employing AFM to study nanostructures had to use a kind of brute force method to locate a single sample on a microscope substrate more than a million times bigger than a target biomolecule The brute force method involves rapidly scanning back and forth across the stage until the tip encounters something interesting There are several problems with this method 1 Since an AFM tip is only a few atoms wide it is delicate and easy to break 2 It s easy to contaminate an AFM tip with unwanted atoms or molecules encountered during the scan and AFM tips can form chemical bonds with both contaminants and biomolecules Such chemical bonds could be a big advantage in studies of individual membrane proteins for example but only if the risk of tip contamination is low 3 Biological samples such as proteins or membranes can be damaged by uncontrolled collisions with an AFM tip A squished sample defeats the purpose of investigating intact biological nanostructures The new laser detection system protects both the AFM tip from physical damage and contamination as well as the sample from harm Plus it s much more efficient From a practical perspective instead of Alison starting to do real science at 4 p m after she s spent most of a day looking for a good sample she can start doing science at 10 a m Perkins says From here on Perkins expects the use of AFM to be less frustrating and more likely to lead to interesting scientific results For example Churnside recently

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