Quantum information processing with Bose-Einstein condensates

Lene Vestergaard Hau

L. E. Reichl, Minh-Binh Tran

Abstract Bose–Einstein condensates (BECs) are starting to play a role in quantum information processing, and there is a need to better understand the dynamical processes at play in the condensates. In this paper, we review recent work on a kinetic model for ultra-low temperature dilute Bose–Einstein condensates that gives correct behavior for first and second sound speeds at very low temperature, and gives explicit expressions and values for decay processes. The predictions of the theory are in agreement with experiment. The method explicitly computes the hydrodynamic modes of the condensate using a method that has also been used to describe decay processes in noble gas mixtures, and thereby opens the way for future analysis of decay processes in BEC mixtures.

Shu Xu, Jörg Schmiedmayer, Barry C. Sanders

Quantum interferometry and quantum information processing have been proposed for Bose-Einstein condensates (BECs), but BECs are described in complicated ways such as using quantum field theory or using a nonlinear differential equation. Nonlinear quantum mechanics does not mesh well with the superposition principle at the heart of interferometry and quantum information processing but could be compatible. Thus, we develop a rigorous foundation for quantum gates, obtained by solving the equation for evolution, and then we employ this foundation, combined with quantum-control techniques and appropriate state-sampling techniques, to devise feasible nonlinear Hadamard gates and thereby feasible, i.e., high-contrast, nonlinear Ramsey interferometry. Our approach to BEC interferometry and quantum logic shifts the paradigm by enlarging to the case of nonlinear quantum mechanics, which we apply to the cases of BEC interferometry and quantum information processing.

Jacob Kekoa Handley

Graeme Whyte, John Veitch, Patrik Öhberg +1 more

We have designed interferometers that sort Bose-Einstein condensates into their vortex components. The Bose-Einstein condensates in the two arms of the interferometer are rotated with respect to each other through fixed angles; different vortex components then exit the interferometer in different directions. The method we use to rotate the Bose-Einstein condensates involves asymmetric phase imprinting and is itself new. We have modeled rotation through fixed angles and sorting into vortex components with even and odd values of the topological charge of two-dimensional Bose-Einstein condensates in a number of states (pure or superposition vortex states for different values of the scattering length). Our scheme may have applications for quantum information processing.

J. M. Raimond