Magnetics Business & Technology - Winter 2013 - (Page 12)

RESEARCH & DEVELOPMENT JILA Physicists Create 'Crystal' of Spin-Swapping Ultracold Gas Molecules Physicists at JILA have created a crystal-like arrangement of In the latest experiment, about 20,000 molecules were trapped ultracold gas molecules that can swap quantum "spin" proper- in an optical lattice, an ordered pattern that looks like a stack of ties with nearby and distant partners. The novel structure might egg cartons created by intersecting laser beams. The lattice was be used to simulate or even only partly filled, with about invent new materials that one molecule per every 10 derive exotic properties lattice wells. The lattice supfrom quantum spin behavpressed the molecules' travel ior, for electronics or other and chemical reactions, alpractical applications. lowing their internal properThe JILA experiment is ties to guide interactions. the first to record ultracold The JILA team used migas molecules exchanging crowave pulses to manipuspins at a distance, a belate the molecules' spins, or havior that may be similar natural rotations around an to that of intriguing solids axis, similar to a spinning such as "frustrated" magtop, to create a "superposinets with competing intion" of two opposite spins ternal forces, or high-temat the same time. Scientists perature superconductors, then observed oscillating which transmit electricity patterns in the average spin without resistance. The reof all the molecules, as well sults build on the same Illustration of the interaction energies between ultracold potassium-rubidium as a falloff or decay in the JILA team's prior creation molecules trapped in a lattice made of intersecting laser beams. The colors indicate spin signal over time, indiof the first molecular quan- each molecule's interaction with the molecule located in the center of the lattice cating the molecules were tum gases and demonstra- (green), for a specific magnetic-field direction (purple arrow). Blue indicates at- swapping spins. tractive interactions, and red indicates repulsive interactions. Darker colors inditions of ultracold chemistry. cate higher interaction energy. Credit: Covey/JILA Scientists calculated the JILA is a joint institute interaction energy that each of the National Institute of molecule experiences with Standards and Technology (NIST) and the University of Colo- all other molecules in the lattice, with the energy intensity derado Boulder. pending on the distance and angle between pairs (see graphic). "One of the main thrusts for our cold molecules research was JILA theorist Ana Maria Rey's modeling of spin oscillations and to realize this interaction, so this is a major breakthrough," NIST/ time periods agreed with the experimental measurements. Ye said JILA Fellow Jun Ye said. "We can now explore very exotic new the spin-swapping interactions entangle the molecules, a signaphases of quantum systems." ture feature of the quantum world that links the properties of NIST/JILA Fellow Deborah Jin points out that "these interac- physically separated particles. tions are advantageous for creating models of quantum magneThe results are expected to open up a new field in which scientism because they do not require the molecules to move around" tists create customized molecular spin models in solid-like structhe crystal structure. tures held in place by the lattice. JILA scientists plan to fill the The JILA crystal has advantages over other experimental lattice more fully and add an external electric field to increase the quantum simulators, which typically use atoms. Molecules, variety of spin models that can be created. made of two or more atoms, have a broader range of properties, The research was funded by NIST, the National Science Founand thus, might be used to simulate more complex materials. Jin dation, the Air Force Office of Scientific Research, the Army and Ye are especially interested in using the structure to create Research Office, the Department of Energy and the Defense Adnew materials not found in nature. An example might be topo- vanced Research Projects Agency. logical insulators, a hot topic in physics, which might transmit data encoded in various spin patterns in future transistors, sensors or quantum computers. The molecules used in the JILA experiments are made of one potassium atom bonded to one rubidium atom. The molecules Send industry news & product releases to Heather Williams are polar, with a positive electric charge at the rubidium end at and a negative charge at the potassium end. This feature means the molecules can interact strongly and can be controlled with electric fields. 12 Magnetics Business & Technology * Winter 2013

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Magnetics Business & Technology - Winter 2013