DIPOLE-DIPOLE INTERACTION IN SQUEEZED VACUA

We study the near-resonant dipole-dipole interaction between two atoms in a broadband squeezed vacuum. We show that this ''vacuum'' modifies the rate of spontaneous emission of the atoms so that it may depend n ot merely on their relative position, as is normally the case, but als o on their center-of-mass position. The explicit form of this latter d ependence is a function of the way squeezing is achieved. We also show that in contrast to the spontaneous decay rate, squeezed vacua do not modify the dipole-dipole potential between the atoms as compared to i ts usual form. Finally, we develop a Monte Carlo wave-function descrip tion of the intraction between atoms with an arbitrary internal struct ure and a squeezed vacuum and apply this formalism to the case of off- resonant excitation of the atoms. We find that in addition to the usua l light shift; the squeezed vacuum results in an additional contributi on to the effective potential governing the evolution of the atomic gr ound states.