Effect of feedback on the decoherence of a Schrödinger-cat state: A quantum trajectory description

Abstract

The linear stochastic Schr\"odinger equation of a cavity mode subject to a homodyne measurement and to a phase-sensitive feedback loop realized with part of the output homodyne photocurrent is derived. We show that quantum feedback has stabilizing effects which manifest themselves in a significant retardation of the decoherence of a Schr\"odinger-cat state. \textcopyright{} 1996 The American Physical Society.