Unified Treatment of Heterodyne Detection: the Shapiro-Wagner and Caves Frameworks

英文摘要：

A comparative study is performed on two heterodyne systems of photon detectors expressed in terms of a signal annihilation operator and an image band creation operator called Shapiro-Wagner and Caves' frame, respectively. This approach is based on the introduction of a convenient operator $\hat ψ$ which allows a unified formulation of both cases. For the Shapiro-Wagner scheme, where $[\hat ψ, \hat ψ^†] =0$, quantum phase and amplitude are exactly defined in the context of relative number state (RNS) representation, while a procedure is devised to handle suitably and in a consistent way Caves' framework, characterized by $[\hat ψ, \hat ψ^†] \neq 0$, within the approximate simultaneous measurements of noncommuting variables. In such a case RNS phase and amplitude make sense only approximately.