Announcements for the Department of Physics at UMBC
November 2010 Archives
November 3, 2010
November 5, 2010
Seminar: Friday, November 5, 2010 at 10:00 a.m
November 10, 2010
Seminar: Wednesday, November 10, 2010 at 3:30 p.m. Coffee 3:15 p.m.
Institute of Fluorescence, University of Maryland Baltimore County, Columbus Center
November 19, 2010
PhD Defense - Hao You
Hao successfully defensed his dissertation on November 19, 2010.
Theoretical Study of Quantum Computation with Nonlinear Optics
Quantum computing has been of intense interest over the last 10 years because of its
promising ability to do high-speed factoring and its potential for the efficient simulation
of quantum dynamics. It could be implemented in many different ways using optical
techniques. A better understanding of the advantages and disadvantages of these
approaches would allow the experimental groups working in this area to optimize their
choice of experiment and to concentrate on the approaches that are most likely to succeed.
In this thesis, we are interested in quantum logic gates based on nonlinear optical
approaches and mainly focus on one of the approaches----quantum Zeno gates. We
theoretically analyze two-photon absorption, which is essential to perform quantum Zeno
gates for coherent light and for frequency-entangled light. We also analyze and compare
quantum Zeno gates with nonlinear phase gates, which is another promising optical
implementation for quantum logic. The results of our theoretical analysis will be useful
for future experimental work in quantum computation.
PhD Defense - Yu Zhou
Yu successfully defended his PhD dissertation on November 19, 2010.
Multiphoton Coherence of Thermal Light
Multiparticle interference is one of the most surprising consequences of quantum mechanics. In quantum theory, interference happens between different yet indistinguishable probability amplitudes. Probability amplitudes can be nonlocal when they are connected with systems including several particles. The interference between these nonlocal probability amplitudes sometimes can only be understood by quantum theory. In this dissertation, the multiphoton coherence of thermal light is studied, theoretically and experimentally, as the consequence of interference between nonlocal probability amplitudes. The study showed that the higher order correlation functions of thermal light had higher contrast compared with the lower order correlation functions. For example, the contrast of the Nth order correlation function of thermal light can reach N!:1. This is because in higher order correlation functions there are more cross terms from interference that contribute to the correlation peak. In this dissertation, the high contrast property is employed to increase the contrast of thermal light ghost imaging. An experiment showed that the contrast of the third order ghost image is significantly improved compared with that of the second order ghost image.