Phase-sensitive manipulations of a squeezed vacuum field in an optical parametric amplifier inside an optical cavity.

A squeezed vacuum field can be amplified or deamplified when it is injected, as the signal beam, into a phase-sensitive optical parametric amplifier (OPA) inside an optical cavity. The spectral features of the reflected quantized signal field are controlled by the relative phase between the injected squeezed vacuum field and the pump field for the OPA. The experimental results demonstrate coherent phenomena of OPA in the quantum regime and show phase-sensitive manipulations of quantum fluctuations for quantum information processing.