UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Experiments in Two-Mode Cavity QED
    (2011) Norris, David Glenn; Orozco, Luis A.; Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Cavity quantum electrodynamics (QED) allows the study of light-matter interactions at the most basic level, through precise identification of the coherent and incoherent (dissipative) parts of the system evolution. We present measurements of light from a cavity QED system consisting of a high-finesse optical resonator coupled to a beam of cold Rb atoms. The novelty of the design lies in the interplay of two degenerate and orthogonal polarization modes. One mode (driven) behaves as the canonical cavity mode of the Jaynes-Cummings Hamiltonian, coherently exciting the atoms with a modest coupling strength; the other mode (undriven) collects a small fraction of spontaneously emitted light and provides a probe of the dissipative processes. We first demonstrate the ability to detect individual atoms passing through the cavity modes in real time by coincidence detection of photons from the undriven mode. Calculation of statistics and correlation functions from the complete photon detection record allows the determination of detection probabilities and the reconstruction of atomic trajectories. We next present evidence of quantum coherence that is created, modied, and measured in the excitation-spontaneous emission cycle. The coherence appears as a long-lived quantum beat at the ground-state Larmor frequency, visible in the intensity autocorrelation function of the undriven mode. Quantum jumps of the atomic state, occurring in between the detections of photons from the cavity, result in substantial changes in the frequency and spectral width of the beats. We present the results of a full quantum Monte Carlo calculation in order to quantitatively explain the measurements.
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    Wiener's Generalized Harmonic Analysis and Waveform Design
    (2007-02-21) Datta, Somantika; Benedetto, John J; Mathematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Bounded codes or waveforms are constructed whose autocorrelation is the inverse Fourier transform of certain positive functions. For the positive function F=1 the corresponding unimodular waveform of infinite length, whose autocorrelation is the inverse Fourier transform of F, is constructed using real Hadamard matrices. This waveform has a autocorrelation function that vanishes everywhere on the integers except at zero where it is one. In this case error estimates have been calculated which suggest that for a pre-assigned error the number (finite) of terms from this infinite sequence that are needed so that the autocorrelation at some non-zero k is within this given error range is `almost' independent of k. In addition, such unimodular codes (both real and complex) whose autocorrelation is the inverse Fourier transform of F=1 has also been constructed by extending Wiener's work on Generalized Harmonic Analysis (GHA) and a certain class of exponential functions. The analogue in higher dimensions is also presented. Further, for any given positive and even function f defined on the integers that is convex and decreasing to zero on the positive integers, waveforms have been constructed whose autocorrelation is f. The waveforms constructed are real and bounded with a bound that depends on the value of f at zero.