Condensed Matter & Surface Sciences

COLLOQUIUM

Chi-Kang "Ken" Shih

The University of Texas at Austin

“Resonantly driving quantum emitters in a cavity”

Semiconductor quantum dots (QDs) possess similar optical properties to that of real atoms and are thus being called “artificial” atoms. In addition to a much larger transition dipole moment compared to their natural counterpart due to their mesoscopic size, QDs be fully tailored, to give rise to the desired electronic properties. These developments bring about new possibilities to explore “quantum optical control” in such nanostructures and to harness these quantum optical properties for novel optical device applications, including the current topic of quantum information technology. Indeed, the realization of driven Rabi oscillations in a two level system and multi-level QD systems, demonstrated fundamental single-qubit and two-qubit quantum operations. All of these demonstrations were achieved on bare quantum dots. In the mean time, significant progress has been made by placing the artificial atoms inside optical cavities to modify their electro-magnetic properties, leading to the so-called “cavity QED” (cavity quantum electrodynamics) with artificial atoms. Indeed, demonstration of the Purcell effect (weak coupling) as well as vacuum Rabi oscillations (strong-coupling) were reported. These cavity-QED experiments, however, demonstrated only “passive” control of quantum state in a sense that the external drive is not used to actively shape the quantum state. While it is expected that achieving active control of QDs in the cavity will open new doors in solid-state based quantum information sciences, there has not been any clear demonstration to date. Here I will report our progress toward this endeavor. In particular we show the achievement of resonantly controlled light emission of quantum dots in the cavity, including (a) nearly ideal fidelity of Rabi flopping using pulse control, (b) direct observation of Mollow triplets in frequency domain, and simultaneously measured first-order and second order correlations, using CW source.

We acknowledge financial support from the National Science Foundation (DMR-0210383, DMR-0606485, DGE -0549417), Texas Advanced Research Program, and W.M. Keck Foundation.

Thursday, October 2, 2008

4:10 p.m. -- Walter Lecture Hall 245