Exact results on the time evolution of the density matrix and the Wigner function for an oscillator with time-dependent frequency are given. Explicit time dependence is given for the case of linear sweep of the restoring force. Such a sweep is shown to generate states of the oscillator with remarkable nonclassical properties such as squeezing and sub-Poissonian character.

• Received 6 August 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.3665