Quantum nondemolition gate operations and measurements in real time on fluctuating signals

摘要

We demonstrate an optical quantum nondemolition (QND) interaction gate with abandwidth of about 100 MHz. Employing this gate, we are able to perform QNDmeasurements in real time on randomly fluctuating signals. Our QND gate reliesupon linear optics and offline-prepared squeezed states. In contrast toprevious demonstrations on narrow sideband modes, our gate is compatible withnon-Gaussian quantum states temporally localized in a wave-packet mode, andthus opens the way for universal gate operations and realization of quantumerror correction.