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  • Trapper Marmot and the Stone Cold Molecules | JILA-PFC
    relatively unexplored terrain of ultracold chemistry Research associate Matt Hummon graduate students Mark Yeo and Alejandra Collopy newly minted Ph D Ben Stuhl Fellow Jun Ye and a visiting colleague Yong Xia East China Normal University have built a magneto optical trap MOT for yttrium oxide YO molecules Figure 1 The two dimensional MOT uses three lasers and carefully adjusted magnetic fields to partially confine concentrate and cool the YO molecules to transverse temperatures of 2 mK It is the first device of its kind to successfully laser cool and confine ordinary molecules found in nature Magneto optical traps for atoms were invented during the 1980s The atom traps made it relatively straightforward for scientists to make ultracold trapped atoms In the process the new traps led to revolutions in the fields of atomic and quantum physics At JILA they were used in the creation of the world s first Bose Einstein condensate the world s first ultracold Fermi gas novel quantum sensors and in dozens of other experiments with ultracold atoms Not surprisingly researchers have been working for nearly 20 years to replicate the success of magneto optical trapping with molecules However molecules are a lot more internally intricate than atoms which typically have two energy levels that can be exploited simultaneously for cooling and trapping them In contrast laser cooling and trapping molecules at ultracold temperatures requires an apparatus that can address multiple energy levels at the same time To meet this challenge Hummon and his colleagues added two additional lasers to their MOT alternated the polarization of the laser light interacting with the molecules and rapidly reversed the direction of the magnetic field around the molecules This combination allowed them to talk to multiple energy levels of the YO molecules at the same time and create a

    Original URL path: http://jila-pfc.colorado.edu/highlights/trapper-marmot-and-stone-cold-molecules (2016-04-29)
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  • The Transporter | JILA-PFC
    information Research associate Tauno Palomaki graduate student Jennifer Harlow NIST colleagues Jon Teufel and Ray Simmonds and Fellow Konrad Lehnert have encoded a quantum state onto an electric circuit and figured out how to transport the information from the circuit into a tiny mechanical drum where is stored Palomaki and his colleagues can retrieve the information by reconverting it into an electrical signal This transportation scheme should make it possible to uses tiny drums for memory storage in quantum computers It also opens the door to using the drums as intermediaries in systems that convert quantum information from one physical system such as a microwave field into another physical system such as a laser light field One interesting aspect of this new scheme is that voltage oscillations describing the quantum state in an electrical signal can be transformed into mechanical energy vibrations in the drum This information transformation is very handy because the drum can store information for much longer than the electrical signal And the researchers can reconvert the drum vibrations into an electrical signal whenever they want to for as long as the drum keeps vibrating The setup for accomplishing this information shape shifting is shown in the figure A microwave field which runs diagonally across the top passes through the square shaped circuit into the drum at the lower left of center The vibrating metal drum is itself part of the electrical circuit transporting the information that makes the drum pulsate This nifty information transporter was described in a recent article in Nature One possible future use for it may be in quantum information processing The transporter can store quantum information in the mechanical energy of the tiny vibrating drum a hundred times longer than it can be stored in other forms of energy Once this quantum

    Original URL path: http://jila-pfc.colorado.edu/highlights/transporter (2016-04-29)
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  • The Big Chill | JILA-PFC
    may well have been even lower because the group s temperature measurement system stopped working at 5 mK This landmark experiment is the first one ever to succeed in cooling a molecule found in nature to ultracold temperatures It comes after nearly two decades of similar but unsuccessful attempts to do the same thing in other laboratories Earlier attempts to cool molecules to ultracold temperatures failed because the molecules studied had too few elastic collisions the kind of collisions in which molecules bounce off one another Thanks to some insightful theory work by senior research associate Goulven Quéméner and Fellow John Bohn however the Ye group opted to cool the OH molecule which the theorists predicted would have elastic collisions more than 90 of the time This collision rate meant that the molecules have enough time to exchange energy so that there are always some molecules with more energy than average and some with less The experiment had several steps First the researchers used a jolt of electricity through a mixture of water vapor and krypton to form the OH molecules Second they used a linear decelerator equipped with an array of highly charged electrodes to slow the molecules down to a speed of 34 meters per second The molecules were brought to a complete stop in the center of a permanent magnetic trap These two steps which have been under development for a decade cooled the molecules down to 50 mK Finally the researchers initiated evaporative cooling which required a neat trick to work The usual approach of flipping a spin in the OH molecules was not good enough in this case to let the hotter molecules escape from the trap So the researchers applied an electric field which opened up some little gateways in the trap that actually

    Original URL path: http://jila-pfc.colorado.edu/highlights/big-chill (2016-04-29)
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  • The Heart of Darkness | JILA-PFC
    light emitted by the laser would fluctuate up and down The researchers wondered what was causing these fluctuations They were especially concerned that whatever it was could also be a problem in future lasers based on the same principles In the group s superradiant laser a million laser cooled rubidium atoms at the heart of the laser act as the primary repository of information In contrast the light field inside the laser is relatively empty or dark The light field can be so dark that it contains on average one or fewer photons quantum light particles Since the light field is so empty the researchers deduced that if the amount of light leaving the laser was fluctuating it must mean that there is some kind of oscillation occurring in the atoms that store the information causing the fluctuation So they decided to peer inside the laser and see for themselves what was going on In particular the group wanted to discover how the process of superradiant lasing was affected by what was happening to the atoms in the heart of the laser Graduate students Justin Bohnet Zilong Chen Josh Weiner and Kevin Cox worked with Fellow James K Thompson to investigate the superradiant laser s stability in response to specific changes in its surroundings This experiment was somewhat like investigating the stability of a bell by hitting it with a hammer and listening to it ring But instead of hammering the superradiant laser the researchers tickled it and used an innovative quantum measurement technique they had previously developed to precisely determine how the atoms were responding To tickle their superradiant laser the researchers decided to use the ordinary everyday laser that routinely makes the rubidium atoms run around between quantum states They simply made the power fluctuate in this tickling

    Original URL path: http://jila-pfc.colorado.edu/highlights/heart-darkness (2016-04-29)
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  • The Amazing Plasmon | JILA-PFC
    nanoparticles the right frequency exquisitely depends on the shape of the particle as well as its size and material Master glass blowers actually figured this out during the Middle Ages They learned to add tiny particles of gold and silver during glass making to produce the vibrant reds blues yellows and purples of the stained glass windows in the great cathedrals of Europe The tiny metal particles were not only responsible for the gorgeous colors but have also prevented the hues from degrading over time in some cases for more than a thousand years Today chemical physicists are working to understand the intricacies of plasmon resonances and their relationship to the photoelectric effect which was first explained by Albert Einstein more than a hundred years ago In the photoelectric effect a photon of light of sufficiently high frequency will eject an electron from a metal surface Even if the frequency of a single photon is not high enough to dislodge an electron intense light can also cause electron ejection Electron ejection occurs when the metal surface simultaneously absorbs several photons whose collectively energy is high enough This multiphoton photoelectric effect is particularly amazing since it usually takes three four or even more photons to eject a single electron Then if the frequency of the light hitting the metal surface happens to resonate with the metal surface s plasmon oscillations billions more electrons will be ejected than would normally occur This plasmon induced photoelectron emission is the subject of intense scrutiny in the Nesbitt laboratory these days Research associate Andrej Grubisic former research associate Volker Schweikhard recently minted Ph D Tom Baker and Fellow David Nesbitt recently completed a study of the critical role of the intense electric field accompanying plasmon resonances in photoelectron emission The presense of such plasmon resonances

    Original URL path: http://jila-pfc.colorado.edu/highlights/amazing-plasmon (2016-04-29)
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  • The Most Stable Clock in the World | JILA-PFC
    to reach the ultimate accuracy Stability is a measure of how noisy a clock is and thus how long the clock has to operate to achieve its ultimate accuracy Recent research in the Ye group focused on improving stability This work has now led to the Sr lattice clock being the most stable in the world by a large margin In addition to improved stability the Ye group continues to rapidly improve the accuracy of the Sr lattice clock The most accurate clocks in the world are currently clocks based on single trapped ions of Al or Hg at the National Institute of Standards and Technology NIST in Boulder But the Ye group s Sr lattice clock is about 40 times more stable than the NIST Al clock i e the Sr lattice clock reaches its ultimate accuracy in a much shorter time The two main sources of noise or jitter that limit stability in optical atomic clocks are clock laser noise and quantum projection noise which comes from not being able to measure the exact quantum state s of the atoms at the heart of these devices This uncertainty is due to the laws of quantum mechanics Until recently the Sr lattice clock laser was the dominant source of noise in the Ye group s optical atomic clock However Martin has now built a new ultrastable clock laser that has been shown to have the world s best performance with a stability of 1 x 10 16 from 1 to 1000 s The new laser has greatly improved the clock s overall stability It has also turned attention towards the reduction of quantum projection noise Quantum projection noise cannot be entirely eliminated however A certain amount of fluctuation in quantum measurements is intrinsic to any system where the laws

    Original URL path: http://jila-pfc.colorado.edu/highlights/most-stable-clock-world (2016-04-29)
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  • The Entanglement Tango | JILA-PFC
    colleagues have discovered that when reactive fermions are at relatively warm micro Kelvin temperatures entanglement evolves naturally In fact the atomic or molecular gas has to be a 10 100 times warmer than your usual ultracold nano Kelvin gas to encourage entanglement Once the temperatures have reached the point where fermions collide and react in pairs atoms or molecules that don t get knocked out of the experiment will be left entangled because they lose their individual identities as a result of being unable to collide Fermions that behave this way include the atoms strontium Sr and ytterbium Yb which are used in atomic clocks and molecules such as potassium rubidium KRb which are used in JILA cold molecule experiments To understand how this entanglement evolves imagine that our quantum gas is a tango dancing party Sr atoms Yb atoms or KRb molecules all of which can exist in one of two possible spin states are the tango dancers Just as the atoms or molecules have two possible spin states there are two kinds of tango dancers men and women And at this quantum dance party women must dance with men and vice versa The catch is that the individual tango dancers all dance a little differently As the dance starts pairs of tango dancers bump into each other As they collide each pair of dancers measures their mutual quantum state to discover whether they dance well together or dance poorly together When a man and a woman who dance well together find each other they tango dance their way right out of the party and go home together Soon all the men and women who dance well have reacted with each other and gone home Now the only ones left at the tango dance are the men and women

    Original URL path: http://jila-pfc.colorado.edu/highlights/entanglement-tango (2016-04-29)
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  • Everything's Cool with Atom | JILA-PFC
    beam of light creating a tiny micron sized trap This trap is called an optical tweezer From the cloud of atoms about 10 atoms are loaded into the tweezer However when light is applied the trapped atoms repeatedly collide in the tiny trap forming molecules These molecules are subsequently lost from the trap About half the time nothing is left in the tweezer because there was an even number of atoms to start with and all the atoms escaped as molecules The other half of the time however there was an odd number of atoms at the beginning In this case a single atom was left in the tiny trap The researchers could see this atom inside the optical tweezer At this point they were ready for the final step cooling this atom to its quantum ground state To further cool the atom the researchers first used two lasers to lower the energy of the atom by one quantum of motion while also flipping its spin Second they shined another laser on the atom which caused the spin to flip back while leaving the atom in its new lower energy state Cooling the atom to its quantum ground state in all three dimensions simply required repeating this two step cycle 75 times The optical tweezer was a key ingredient in the cooling process During the second step in which a laser flips the atom back into its original spin state for example the tweezer holds the atom tightly in place This confinement makes it far less likely that the laser will accidentally excite the atom to a higher energy state which would prevent the cooling from happening After the cooling the researchers were able to tell when the atom had reached its quantum ground state When the atom is in

    Original URL path: http://jila-pfc.colorado.edu/highlights/everythings-cool-atom (2016-04-29)
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