Phase-admixed states: Coherence and incoherence

Publisher Website
Google Scholar
Abstract
The standard Glauber coherent states associated with a given boson or oscillator mode have a well-known decomposition in terms of the occupation-number eigenstates. In this paper we study a much more general class of quasicoherent states in which each term of this decomposition acquires its own extra phase factor. These new states are not minimum-uncertainty states, but we show that they may be represented as eigenstates of some new canonical annihilation operator which is obtained from the original one by an appropriate unitary transformation. By choosing particular sets of values for the phases which characterize the quasicoherent states, we show how we are thereby able to study, for example, the effects of (i) optical propagation through a nonlinear medium with an intensity-dependent refractive index, and (ii) phase incoherence caused by the stochasticity typical of an optical source. The quasicoherent states are shown to share many of the same coherence properties as the original Glauber states. Nevertheless, they exhibit a mixture of coherent and incoherent properties. This is particularly illustrated by the important practical example where the phase angles are randomized.