Research On The Quantum Information Storage Based On Single Photon Detector And Raman Scattering

The quantum secure communication is a new generation of communication where the photons are acted as the information carrier. The appearance of the quantum memory provides solution for the long distance quantum secure communication and realizes the relaying transmission, which solves the problem of the short communication distance. In this paper the theory of the single photon detector is researched and the experiments based on the time-correlated single photon counting techniques are carried out, the stokes-light of the stimulated Raman scattering of 85 Rb have been detected based on the optimizing design of the light path of the experiment. Theoretical analysis on the conditions of the stimulated Raman scattering and the detection on the Stokes light are carried out based on the theoretical knowledge of the single photon detector, the time-correlated single photon counting technique and the storage of quantum information based on the Raman scattering. The properties of the time correlation characteristics are studied by the self-made pulse laser and the signal generator which triggers the voltage signal. The principle and the influence of the crosstalk peak of the APD are studied; the relationships between the distance of the crosstalk peak and the fiber length and the relationships between shape of crosstalk peak and the avalanche current are obtained. The photonic emission of Si-based cipher chips is studied and the contrast experiment shows that the scheme with the time-correlated single photon counting card achieves a higher efficiency and a lower background noise comparing with that of the oscilloscope. The stimulated Raman scattering experiment system is designed and the characteristics of the laser, the light polarization devices, the optimization of the polarized light and the amplification of the voltage signal circuit are studied systematically. Based on the saturated absorption spectroscopy technology, the technical proposal of the locked of laser frequency is proposed by the control on the scan voltage and the DC bias parameters, which is important for the stimulated Raman scattering experiments based on the medium of Rb85.The storage of the quantum information is realized by the stimulated Raman scattering of Rb85 in form of collective excitations of the atomic ensemble, the Stokes light is detected successfully and further studies on the influence of the length of Rb Cell, the temperature of Rb Cell and the detuning of the write light are also carried out.