Generation of Squeezed States by Molecular Collisions

Hai-Woong Lee

Vladimir Yurovsky

Bose-Einstein condensate (BEC) is considered under conditions of Feshbach resonance in two-atom collisions due to a coupling of atomic pair and resonant molecular states. The association of condensate atoms can form a molecular BEC, and the molecules can dissociate to pairs of entangled atoms in two-mode squeezed states. Both entanglement and squeezing can be applied to quantum measurements and information processing. The processes in the atom-molecule quantum gas are analyzed using two theoretical approaches. The mean-field one takes into account deactivating collisions of resonant molecules with other atoms and molecules, neglecting quantum fluctuations. This method allows analysis of inhomogeneous systems, such as expanding BEC. The non-mean-field approach -- the parametric approximation -- takes into account both deactivation and quantum fluctuations. This method allows determination of optimal conditions for formation of molecular BEC and describes Bose-enhanced dissociation of molecular BEC, as well as entanglement and squeezing of the non-condensate atoms.

L.-M. Duan, Anders Søndberg Sørensen, J. I. Cirac +1 more

We propose and analyze a scheme for generating entangled atomic beams out of a Bose-Einstein condensate using spin-exchanging collisions. In particular, we show how to create both atomic squeezed states and entangled states of pairs of atoms.

A. F. R. de Toledo Piza, Nicim Zagury

Harry J. Kimble

Ray‐Kuang Lee, Yinchieh Lai, Yuri S. Kivshar

We study quantum correlations and quantum noise in soliton collisions described by a general two-soliton solution of the nonlinear Schr\"odinger equation by using the back-propagation method. Our results include the standard case of a sech-shaped initial pulse analyzed earlier. We reveal that double-hump initial pulses can get more squeezed and the squeezing ratio enhancement is due to the long collision period in which the pulses are more stationary. These results offer promising possibilities of using higher-order solitons to generate strongly squeezed states for the quantum information process and quantum computation.