Coherent population trapping in the Λ system by a two-mode quantized field in an SU(2) coherent state

Abstract

Coherent population trapping (CPT) in a three-level system in the Λ configuration interacting with two quantized fields is studied. It is shown that, in addition to the known trapping states of the field involving ordinary coherent states of each mode, SU(2) coherent states associated with the Schwinger realization are also field states that give rise to CPT for this system. In addition it is pointed out that superpositions of such states, and statistical mixtures of them, for different total photon numbers also give rise to CPT. The stability of the CPT states against decay of the cavity field modes is examined. CPT is preserved if the modes decay at the same rate. A possible method for generating statistical mixtures of the SU(2) coherent states is described.