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Vortices: What’s happening inside ultracold quantum storms?

Recently published computer simulation of what happens to a planar condensate of highly magnetic ultracold atoms that have been bathed in laser beams designed to enhance the interactions among the atoms.  The arrows depict the average magnetic spin orientation at that place in the condensate.  In this particular spin texture, a collection of atoms with spins pointing down (blue arrows) circulate around a sample of spin-up atoms (red arrows). Note the circulation, but in this case, the core is filled. Credit: Brandon Anderson

Vortices pop-up in the weather, sink drains, and even astrophysics; they are also a feature of quantum superfluids, such as an ultracold atomic gas. Quantum physics dictates that the circulation in these systems obeys certain quantization criteria. When a superfluid is disturbed vortices will form in order to satisfy this circulation constraint. Vortices look like mini-tornados, having an essentially empty core or “eye” with the surrounding atoms circulating.

Stirring up a superfluid is one way to induce vortices. Changing the interactions of the system can also do this—for instance introducing spin-orbit coupling.  Vortices even nucleate as a thermal gas undergoes a phase transition into a Bose-Einstein condensate. Another cool aspect: in seeking out the lowest energy configuration, the vortices will arrange into a lattice (see image below, data taken and image created by W. Ketterle group @ MIT)

Read more to learn more about coreless vortices—a quantum storm without the ‘eye.’

Recently JQI researchers used computer simulations to predict the behavior of magnetic atoms in a dipolar Bose Einstein condensate. When the atoms were subjected to additional laser beams the magnetic interactions among the atoms caused them to sort into striking spin texture patterns, including a “coreless vortex,” a condition in which one component of the atoms circulated around another component of atoms at rest in the middle (See image in above gallery).

Vortex lattice from MIT Ketterle group

Recent Quantum Bits

October 17, 2016

Check out the second half of our feature story on Weyl semimetals and Weyl fermions, new materials and particles that have become a major focus for condensed matter researchers around the world. Part two looks at some of the theoretical work going on at JQI and CMTC. If you missed part one, it's not too late to catch up on the series. And if you missed our roundup of the research that led to last week's Nobel Prize in Physicsresearch that is closely related to Weyl materialswe encourage you to take a look.

JQI is also happy to congratulate Karina Jiménez-García on receiving a 2016 L'Oréal-UNESCO For Women in Science fellowship. "This is a recognition that I owe to all those that have guided and inspired me and those who have supported me throughout my professional career, especially my family," Jiménez-García said. We wrote a short story on how she plans to use the fellowship funds. It links to stories about the research she worked on while visiting JQI.

October 6, 2016

This year's Nobel Prize in Physics was awarded to three researchers who helped bring topology into physics. It's an innovation that has propelled condensed matter physics for the past three decades, leading recently to the discovery of several exotic materials.

We put together a roundup (http://jqi.umd.edu/physics-nobel-topological-exotic-matter) of the research that led to the prize and offered our take on topology. (Yes, we resorted to pastries.)

This year's prize is timely, too, as today we published part one (http://jqi.umd.edu/news/warm-welcome-weyl-physics) of a two-part series on Weyl semimetals, topological materials with a long history. That history is due, in part, to this year's laureates: David Thouless, Duncan Haldane and Michael Kosterlitz.

Part one focuses on the history and basic physics of Weyl materials. Part two, which will appear next week, focuses on some of the research being explored by physicists at JQI and the Condensed Matter Theory Center at the University of Maryland.

September 15, 2016

From self-driving cars and IBM’s Watson to chess engines and AlphaGo, there is no shortage of news about machine learning, the field of artificial intelligence that studies how to make computers that can learn. Recently, parallel to these advances, scientists have started to ask how quantum devices and techniques might aid machine learning in the future.

To date, much research in the emerging field of quantum machine learning has attacked choke points in ordinary machine learning tasks, focusing, for example, on how to use quantum computers to speed up image recognition. But Vedran Dunjko and Hans Briegel at the University of Innsbruck, along with JQI Fellow Jake Taylor, have taken a broader view. Rather than focusing on speeding up subroutines for specific tasks, the researchers have introduced an approach to quantum machine learning that unifies much of the prior work and extends it to problems that received little attention before. They also showed how to increase learning performance for a large group of problems. The research has been accepted for publication in Physical Review Letters.

Quantum-enhanced machine learning. V. Dunjko, J. M. Taylor and H. J. Briegel, Physical Review Letters, to appear. arXiv: http://arxiv.org/abs/1507.08482.

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