Optical Rephasing Techniques with Rare Earth Ion Dopants for Applications in Quantum Information Science

Quantum Information;Rare Earth Ion Dopants;Optical Rephasing

Ledingham, Patrick Matangaro ; Longdell, Jevon Joseph ; Sellars, Matthew

University of Otago

关键词: Quantum Information;    Rare Earth Ion Dopants;    Optical Rephasing;   

Others  :  https://ourarchive.otago.ac.nz/bitstream/10523/2001/3/LedinghamPatrickM2011PhD.pdf

美国|英语

来源: Otago University Research Archive

【 摘 要 】

This thesis explores the use of cryogenic rare earth ion doped solids for applications in quantum information science. A theoretical analysis of optically rephased memory protocols, namely the two pulse photon echo, is developed. This analysis is a fully quantum mechanical analysis. The two pulse photon echo suffers from collective amplified spontaneous emission in the output mode due to gain along the direction of propagation. This noise can be ;;rephased;; with a pi pulse, much like a two pulse photon echo, resulting in time separated nonclassical correlations. This thesis aims to characterize this noise and experimentally realize these nonclassical correlations. A theoretical analysis is presented for a hybrid photon echo rephasing protocol. The protocol uses strong optical rephasing pulses as well as external electric fields to rephase coherence in a two level ensemble of atoms. The Stark effect is utilized to reduce the collective spontaneous emission caused by inversion. We find that the protocol is noise free and has a theoretical maximum efficiency of 54% in the forward direction and 100% in the backward direction. The necessary task of laser frequency stabilization is presented in this thesis. The laser is locked using electronic and optical feedback, named the ;;hybrid;; lock. A theoretical analysis is presented as well as experimental results. The laser locking was sufficient for phase stable photon echo experiments to be conducted. Three experiments are presented in this thesis. The first experiment involved the characterization of the detection mode and the two pulse photon echo. Benchmark values are given to the photon echo efficiency, echo lifetime and Rabi frequency. The second experiment is the characterization of the amplified spontaneous emission from inverting a two level ensemble of cryogenic rare earth ions doped in a solid. These experiments were conducted on different optical depths on the inhomogeneous line of Tm:YAG. We find that indeed there is phase independent noise after the inversion with a bandwidth given by the Fourier width of the inverting pulse. It was seen that the noise measured increased exponentially with the optical depth, as expected from the theoretical analysis. The third experiment was the measurement of rephased amplified spontaneous emission and the nonclassical time separated correlation between the noise and the rephased noise. As outlined by the theory, the amplified spontaneous emission can be rephased with a pi pulse. This experiment is implemented on different optical depths on the inhomogeneously broadened line of Tm:YAG. For optical depths of 0.25 and greater, it was seen that the correlations were classical. For an optical depth of 0.046, the correlation was seen to violate the inseparability criterion. This violation of the criterion means that the ASE and RASE fields can not be described as a separable state. This correlation measurement was made with a confidence interval of 95.15%.