CPM Seminar

Optimal Quantum Control of Excitonic Qubits in Semiconductor Quantum Dots

Kimberly Hall

Department of Physics and Atmospheric Science
Dalhouse University

Femtosecond pulse shaping provides a flexible approach to tailoring the Hamiltonian governing the interaction of light with matter. Together with powerful adaptive feedback algorithms, this approach is now used routinely in the control of a variety of physical processes. For quantum computing applications, pulse shaping provides a means to optimize the speed and fidelity of elementary quantum gates, and may enable the realization of schemes for complex instruction set quantum computing. In this presentation, I will discuss our recent experiments demonstrating ultrafast quantum control of charge based (exciton) qubits in semiconductor quantum dots. Using optimal quantum control techniques, we show that pulse shaping provides a means to optimize the fidelity of a C-ROT gate in single quantum dots [1,2], and enables parallel single qubit gates on distant quantum dots within the laser focal spot [3]. We also demonstrate adiabatic rapid passage on a subpicosecond time scale in single semiconductor quantum dots, yielding new insight into the role of phonons in dephasing of exciton qubits [4].

[1] A. Gamouras, R. Mathew, and K. C. Hall, J. Appl. Phys. 112, 014313 (2012).
[2] R. Mathew, C. E. Pryor, M. E. Flatte, and K. C. Hall, Phys. Rev. B 84, 205322 (2011).
[3] A. Gamouras, R. Mathew, S. Freisem, D. G. Deppe, and K. C. Hall, Nano Letters 13, 4666 (2013).
[4] R. Mathew, E. Dilcher, A. Gamouras, A. Ramachandran, Hong Yi Shi Yang, Sabine Freisem, Dennis Deppe, and Kimberley C. Hall, Phys. Rev. B 90, 035316 (2014).