Synopsis: Undoing a Quantum Knot

October 16, 2019

Researchers have noticed the decay of a topological knot defect in a quantum gasoline.

Synopsis figure

T. Ollikainen/Aalto College

Bodily theories for a lot of states of matter predict the existence of defects—vortices, knots, or monopoles—whose topology makes them exceptionally secure. This “topological safety” could clarify persistent buildings starting from so-called skyrmions in magnetic supplies to stringy textures of the cosmos. To raised perceive these defects, researchers create and research them in extremely controllable techniques like quantum condensates. Now, Tuomas Ollikainen of Aalto College, Finland, and coworkers have ready a knot in a Bose-Einstein condensate (BEC) after which perturbed the condensate in order to “untie” the knot. Their work delivers the primary time-resolved “film” of a quantum knot’s decay.

Constructing on a 2016 research, the researchers ready a knot by making use of a spatially structured magnetic area to a BEC condensate of rubidium atoms. The ensuing knot consisted of a specific configuration of magnetic ordering: Traces plotting the native magnetic axis inside the BEC shaped closed, mutually interlocked circles. The staff perturbed the system by eradicating the sphere after which imaged the BEC to observe how the knot developed.

The experiments—carried out at Amherst Faculty in Massachusetts—revealed two phases of the BEC dynamics. For the primary few milliseconds after the perturbation, the knot endured however the condensate state modified, with a number of ferromagnetic islands rising inside the initially nonmagnetic BEC. Inside a couple of hundred milliseconds, nonetheless, the knot totally dissolved, and a ferromagnetic section shaped on the periphery of the condensate, surrounding a nonmagnetic core. A special topological defect appeared between the 2 magnetic areas, with the defect consisting of atomic spins organized in a vortex. Discovering similarities with earlier theoretical research on monopole defects, the researchers recommend that this transition right into a spin vortex might be a typical characteristic of many sorts of topological defects.

This analysis is revealed in Bodily Evaluation Letters.

–Matteo Rini

Matteo Rini is the Deputy Editor of Physics.

Topic Areas

Atomic and Molecular PhysicsQuantum Physics

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