Coherent Optical Spectroscopy of a Single Semiconductor Quantum Dot.

[摘要] The quantum optoelectronic properties of semiconductor quantum dots (QDs) have featured prominently in numerous scientific proposals,including quantum computing, single photon sources, and spintronic devices. QDs are particularly attractive for these applicationsbecause not only do they behave in many ways as simple stationary atoms with discrete states, but also because they are better than atomic systems since they are customizable. In this thesis, efforts have been made to understand and control the physical properties of a single quantum dot by coherent continuous wave optical spectroscopy.In this thesis, the QD driven by a strong optical field is studied. Autler-Townes splitting has been demonstrated in a neutral QD and the Mollow absorption spectrum has been demonstrated in both neutral and charged QDs. The results show that the QD state behaves like a single atom even in the high optical field strength limit and can beswitched at a rate up to 1.6 GHz with low power cw diode lasers.One of key requirements for fault tolerant quantum computation is fast qubit initializations. In this thesis, fast electron spin state initialization is realized in a single negatively charged QD by an optical pumping technique. The spin initialization rate on the order of 10^9 s^-1 is achieved with an optical pumping efficiency of 99%.Coherent population trapping of an single electron spin is also realized in a single QD, which demonstrates the optical generationof electron spin coherence and arbitrary spin state initialization. The results show that spin based semiconductor QD systems have thepotential to be used for electromagnetically induced transparency, slow light, and quantum information storage applications.By using the developed coherent population trapping technique, the optically controlled locking of the nuclear field is demonstrated,which leads to an enhancement of the electron spin coherence time by a factor of ~40. This lays the groundwork for preparing the nuclear spin environment in a simple and reproducible fashion over long time scales, minimizing the statistical broadening in future experiments involving repetitive spin control and measurement.

[发布机构] University of Michigan

[效力级别] Quantum Dots

[关键词] Nonlinear Spectroscopy;Quantum Dots;Quantum Computation;Optics;Spin;Physics;Science;Physics