To implement solid-state quantum information processing, precision control of quantum states in single quantum dots including charges, spins and wavefunctions are highly desirable. For a single quantum dot based photocurrent device, single hole spins were initialized with a high fidelity by controlling carrier tunneling rates with a resonant excitation, The tunneling rates are tuned by controlling the wavefunciton spread with an external magnetic field. In addition, many-body exciton states in a coupled system with a single self-assembled quantum dot and a wetting layer are observed by strong anomalous diamagnetic shifts. A tremendous positive diamagnetic coefficient is observed when an electron in the wetting layer combines with a hole in quantum dot, which is nearly one order of magnitude larger than that of the excitonic states confined in quantum dots. When the electrons recombine with holes within quantum dot in the coupled system, a peculiar negative diamagnetic effect is observed.
To scale up the quantum dot-based quantum photonic network, photonic crystal cavities with high quality factors around 10000 are fabricated with single quantum dots located in antinode position of the cavity. Selective spin enhancement from single quantum dots in the cavity are observed for each branch in Zeeman splitting because of the Purcell effect, particularly can be precisely controlled with a vector magnetic field. Strong coupling for cavity QED between different excitonic states in a single quantum dot and the cavity will be presented, which has potential applications in realizing quantum nodes for quantum photonic network.
Xiulai Xu, Kai Peng, and Chenjiang Qian, "Quantum state control in single quantum dots and the coupling with photonic crystal cavities (Conference Presentation)," Proc. SPIE 10518, Laser Resonators, Microresonators, and Beam Control XX, 105180Q (Presented at SPIE LASE: January 30, 2018; Published: 14 March 2018); https://doi.org/10.1117/12.2288762.5751426589001.
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