Quantum-nondemolition measurement of the photon number using cross-polarized soliton collisions in a fiber loop interferometer

Summary form only given. Quantum-nondemolition (QND) measurements are those that do not disturb the quantum distribution of the variable being measured. It has been experimentally demonstrated that QND measurement of the photon number an be achieved by use of wavelength-multiplexed soliton collisions. A quantum analysis of the experiment has also been developed. It was found that the phase spreading of the probe as a result of self-phase modulation can contribute significant noises. In this paper we propose a new and better QND scheme using cross-polarized soliton collisions in a fiber loop interferometer. The scheme requires only a single wavelength laser source and can be fully fiber-integrated, and, most importantly, the noise caused by self-phase modulation is automatically suppressed by detection of the squeezed quadrature of the probe soliton.