Quantum stochastic resonance in symmetric systems

Abstract

We investigate the low-temperature quantum stochastic resonance (QSR) phenomenon in a two-level system (TLS) which is coupled to an Ohmic heat bath. In contrast to common belief we find that QSR occurs also for symmetric (i.e., unbiased) TLS’s if the viscous friction parameter [Formula Presented] exceeds a critical value: We demonstrate that with respect to the spectral power amplification measure QSR always occurs for [Formula Presented]; in contrast, the output signal-to-noise ratio exhibits an amplification only for [Formula Presented]. © 1999 The American Physical Society.