Following a Single Imperfection

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Science  15 Mar 2013:
Vol. 339, Issue 6125, pp. 1255
DOI: 10.1126/science.339.6125.1255-b

Quantum simulation aims to explain the behavior of a complicated physical system by using a more ordered and controllable equivalent. Over the past decade, such quantum simulators have been realized in quantum gases loaded in optical lattices, which simulate crystal structures in real materials and are formed by counterpropagating laser beams. Quantum magnetism, which is thought to play a major role in high-temperature superconductors and spin liquids, is a prime goal for such efforts. Fukuhara et al. observed the dynamics of a single spin impurity in a linear chain of ∼10 atoms with magnetic interactions as the regime was varied from deep confinement to a delocalized superfluid state. The impurity was created with exquisite control by flipping the direction of the middle spin in the chain, whereas the other spins remained in the initial uniform state; the propagation of the impurity was tracked by imaging individual sites. The results agreed well with numerics and showed evidence of collective polaronic behavior in the superfluid limit.

Nat. Phys. 10.1038/nphys2561 (2013).

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