Cavity QED and Confined Phonons in Semiconductor Quantum Dots

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This research is focused on coherent manipulation and cavity QED of confined phonons in semiconductor quantum dots. In colloidal quantum dots such as CdSe nanocrystals, not only electronic energy levels but also lattice vibrations are completely quantized. Properties of confined phonons in these quantum dots will be investigated and exploited for the development of a mesoscopic system in which a single or an array of quantum dots couple strongly to a single mode of electromagnetic fields. Coherent nonlinear optical techniques will be developed and used for the optical excitation and detection of confined acoustic phonons in these quantum dots. Optical manipulation at the level of a single phonon per quantum dot, and understanding decoherence of quantized mechanical excitations in a nanomechanical system are important goals. A cavity QED system where confined acoustic phonons coupling to a high-Q whispering gallery mode in a fused silica microsphere through a driven two-photon Raman transition will also be developed. The proposed cavity QED system provides a unique model system for isolating and manipulating fundamental dynamical processes in simple quantum systems and for creating controlled entanglement of quantum dots. In addition to potential applications in quantum information processing, the ability of optical manipulation of confined phonons in colloidal quantum dots can also stimulate further applications of these quantum dots as nanomechanical systems in areas such as biology. The research program provides training for graduate and undergraduate students in cutting edge research techniques in areas including optics, semiconductor physics, nanotechnology, and quantum information that are of both scientific and technological importance. This training will prepare them for a range of careers in academe, industry, and government. This research program is focused on studies of electronic and mechanical excitations in semiconductor quantum dots. In semiconductor quantum dots such as CdSe nanocrystals with a dimension of a few nanometers, both electronic and mechanical excitations are completely quantized or completely discrete. Properties of electronic and mechanical excitations will be investigated by using coherent nonlinear optical techniques and will be exploited for the development of a mesoscopic system in which a single or an array of quantum dots couple strongly to a single mode of electromagnetic fields. This composite quantum dot microcavity system can be used for the coherent manipulation of dynamical processes in simple quantum systems and for the exploration of quantum information processing, an area of considerable technological importance. The ability of optical manipulation of mechanical excitations in semiconductor nanocrystals can also stimulate further applications of these quantum dots as nanomechanical systems in areas such as biology. Students involved in this program receive rigorous training in areas including optics, semiconductor physics, nanotechnology, and quantum information that are of both scientific and technological importance and can pursue careers in academe, industry, and government.