Bibliography: p. 135-145,Some pages are in colour.,
Paul traps are used in many different fields of physics to contain ions for different purposes. Give the oscillating fields that this type of trap employs to trap an ensemble and the heating that the interactions of these fields with multiple ions can cause, cooling the system could be of great interest, and there are several methods of doing so. This study explores on of these methods, evaporative cooling, applied to a type of Paul trap, a Linear Paul Trap (LPT), using computer simulations. This thesis will first describe a trapped ion ensemble and an evaporation event both physically and how it is computationally modeled. IT then proceeds to discuss the conditions for which evaporative cooling applied to an LPT could be optimized to maximize the chances of achieving highest temperature per particle evaporated.
The dynamic response and wake of a circular cylinder undergoing vortex-induced vibrations (VIV) is investigated experimentally using a cyber-physical force-feedback system and particle image velocimetry (PIV) measurements. The effects of the structural mass ratio and mass-damping on the VIV amplitude and frequency response are investigated at a constant Reynolds number by manipulating the structural mass, stiffness and damping in the cyber-physical system. The extent of amplitude modulations in VIV is investigated and a new metric is proposed to quantify the extent of amplitude modulations. A methodology for extracting relevant flow physics associated with coherent structures in the flow is presented for VIV data. Low-order models (LOM) are proposed to describe the dynamics of the wake in each of the VIV branches based on the evolution of the modal temporal coefficients obtained from the proper orthogonal decomposition (POD). The low-order modelling approach is re fined by including a phase-averaging term to better model cases where significant spatial oscillations of the velocity field occur.
Contributors:Prasad, Adarsh Shankar
Precise information about the temporal mode of optical states is crucial for optimizing their interaction efficiency between themselves and/or with matter in various quantum communication devices. Here we propose and experimentally demonstrate a method of determining both the real and imaginary components of a single photon's temporal density matrix by measuring the autocorrelation function of the photocurrent from a balanced homodyne detector at multiple local oscillatorfrequencies. We lay the theoretical foundation for our work and describe the experimental methods involved in detail. We show the results of testing our method on single photons heralded from bi-photons generated via four-wave mixing in an atomic vapor. We develop an appropriate theoretical model for our experimental settings and describe the involved calculations explicitly. The obtained experimental results show excellent agreement with theoretical predictions for the various settings involved.
Contributors:Barrios Barocio, Erick
Bibliography: p. 94-97,Many pages are in colour.,This thesis reports the realization and applications of a versatile wideband balanced homodyne detector operating in the time domain and intended for Quantum Optical Tomography. The detector can work with high repetition rate lasers used for the production and measurement of the electric field quadratures of quantum states of light. Full characterization of the detector by shot-noise measurements and by verifying its capability to reconstruct the density matrix and Wigner function of various states of interest is given. By overcoming photodiodes response mismatch, high frequency electronics issues and by choosing an appropriate optical set-up, a high level of common mode suppression (52.4dB) and a low electronic noise gave a shot-to-electronic noise ratio of I3dB for a Local Oscillator with 6.2 x 108 photons-per-pulse on a ~ 100MHz bandwidth. Results for the characterization of a single-photon Fock state are presented. An average efficiency of 56% was obtained for the generation/detection of the state.,