Abstract
A quantum analysis of the interaction of two propagating, quasimonochromatic fields with three-level Λ-type atoms is presented. It is shown that the recently predicted effect of pulse matching [S. Harris, Phys. Rev. Lett. 70, 552 (1993)]–the generation of fields with matched Fourier components–is due to the nonadiabatic response of the medium. This effect leads to a correlation of the high-frequency phase fluctuations of the fields, and may therefore be used to reduce the noise in short-time measurements of phase differences.