Squeezing with Laser Cooled Atoms

E. Giacobino, Astrid Lambrecht, Jean-Michel Courty +1 more

Yaakov Shevy

The process of laser cooling in a quasi resonant standing laser wave is one of the principal technics of laser cooling of atoms. Recent advances in this field include breaking both the "Doppler and the recoil limits". On another front modification of the quantum statistical properties of the "vacuum" fluctuations by squeezing has been achieved in the laboratory. It is, therefore, interesting to find what is the nature of the modification of the laser cooling process when the atoms are also embedded in squeezed vacuum. Such a state can be produced in principle by a degenerate parametric amplifier whose input are vacuum fluctuations. It is shown that due to the modified decay rates of an atom which is embedded in such a state, profound modification of the cooling processes in a standing wave is achieved . Among the important results obtained is the change of sign of the stimulated force from a heating force in normal vacuum to a cooling force in squeezed vacuum. This phenomenon can result in cooling forces more than two orders of magnitude larger than the maximum force in normal vacuum. In this talk the method for calculating the force in squeezed vacuum will be given. The modified force will be compared to the force in normal vacuum and finally the practical implications of these results for laser cooling will be discussed.

Robert Graham, Daniel F. Walls, Weiping Zhang

In this paper, the use of squeezed light in laser cooling is investigated. We find that in a traveling-wave laser field, a two-level atom in a squeezed vacuum cannot be cooled to a lower temperature than in normal vacuum. For a two-level atom in a standing-wave laser field, if it is tuned from the resonant region, the conclusion is the same as in the traveling-wave case. However, near the resonant region, the atom in a standing-wave field can achieve a lower temperature than Doppler limit.

Hidekazu Hachisu

Lei Tan, Cuiling Zhang, Jinfang Zhang +2 more

A theoretical study is carried out for the laser cooling of a moving three-level atom in a ladder configuration, driven by a bichromatic laser fields with a broad-band squeezed vacuum. The friction, diffusion coefficients and the equilibrium temperature are calculated numerically and shown graphically as a function of two-photon detunings for various cases of the squeezed vacuum. It is shown that the relative phases between the two coherent fields and the squeezed vacuum field play an important role in the cooling process. For a suitable choice of parameters, the atomic cooling temperature may be reduced to below that in the case of a vacuum, even down to two orders below the Doppler temperature limit. The efficiency of this cooling scheme is also analyzed.

Steven Chu, Mara Goff Prentiss, A. Cable +1 more