Generation And Applications Of The All Fiber Source Of Pulsed Twin Beams

Twin-beams are two separable beams of light with quantum correlation, so thatthe photon number fluctuation is even smaller than the shot-noise limit of twocoherent light. And the state of the art in generating twin-beams is to generate fromhigh gain non-degenerate parametric amplifiers. The continuous variable nature of atwin-beams provides much higher energy, detection efficiency, and capability ofpreparing quantum states deterministically, which all beat the discrete counterpart.Hence, twin-beams have great application prospects in both quantum information andquantum measurement techniques. In this thesis, we study the generation of pulsedtwin-beams in an all fiber system on both theoretical and experimental aspects. Theresearch work can be summarized as following parts:(1) Theoretically, we derive a multi-mode linear model for pulse pumped highgain fiber optical parametric amplifier, and the noise performance of the fiber opticalparametric amplifier is analyzed using this model. The photon number gain, intensitynoise and intensity difference noise of a fiber optical parametric amplifier with weakinjection are analyzed numerically. The experiment parameters in twin-beamsgeneration are also studied as guidance to experimentally generating twin-beams withhigh intensity difference squeezing rate.(2) We study the noise detection technique of pulsed light and design adifferential detector for quantum noise measurement of pulsed light. The differentialdetector uses a transformer to suppress the thermal noise of the load resistor, and lowpass filters to eliminate the side-effect from the beating signal of the laser pulse. Afterthat, the differential current is amplified by low noise amplifiers. The design abovegives this differential detector high signal to noise ratio and common-mode rejectionratio, and makes it well-qualified for conducting direct differential detection orhomodyne detection over pulsed light source in quantum optics.(3) Using mode-locked fiber laser and dispersion-shifted fiber, weexperimentally build an all-fiber source of pulsed twin beams in the telecom band.The intensity-difference noise of the twin-beams is lower than the shot noise limit by3.1dB (10.4dB after correction for losses), which is the highest degree of intensitydifference squeezing in fiber system to date. Moreover, the influence of experimentalfactors on the noise reduction of the twin-beams of light is analyzed.(4) We discuss the entanglement of the quadratures of signal and idler field generated from a non-degenerate FOPA theoretically. A series of puled entanglementmodes are obtained by using the singular-value decomposition of the joint spectrumfunction, and the mode matching in detection process is discussed. After that, thespecific mode structure is analyzed numerically for fibers with different dispersionparameters. These results help to generate and detect quadrature entanglement state infiber system.