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Thursday, November 03, 2011
12:30 PM - 2:00 PM
T-DO Conference Room Bldg 123

Quantum Lunch

Quantum Quenches in an Optical Lattice

Brian DeMarco
Department of Physics University of Illinois

The study of non-equilibrium phase transitions is wide ranging, touching on topic as diverse as the formation of structures in the early Universe and the practicality of quantum computing. Recently, interest has turned to the theory of quenches across quantum phase transitions. “Quench” in this context refers to rapidly varying a parameter in the Hamiltonian in order to tune between ground-state quantum phases. While there has been a great deal of theoretical attention paid to this problem, experimental study has been scant. I will talk about our recent measurements of quantum quenches across the bosonic Mott-insulator–superfluid phase transition accomplished using an optical lattice. We trap ultra-cold atoms in a crystal of light—an optical lattice—created from the intersection of laser beams. By rapidly changing the intensity of the laser light, we quench the atoms between a localized Mott insulator and a superfluid state. We observe that excitations such as vortices are created during this process. We show that the number of excitations is proportional to the fraction of atoms crossing the phase boundary and has a power-law dependence on the quenching rate. I will also briefly mention our recent demonstration of Anderson localization of 3D quantum matter waves.