COLLOQUIUM, Department of Electrical and Computer Engineering
Modeling of Coherent Solid-State Quantum Computing Devices
NSF Center for Quantum Device Technology
Clarkson University, Potsdam, NY
We present our program of theoretical study of nuclear-spin and other solid-state quantum computing devices. We aim at developing techniques for evaluation of decoherence and relaxation in systems which are candidate for quantum computing implementations. Results include systematic investigation of interactions and decoherence in semiconductor quantum wells and heterojunctions, with initial applications for nuclear spins. Our starting system for these theoretical studies have been nuclear spins in semiconductor layered structures, in the regime of low temperature and high magnetic field. The electron system is then in the quantum Hall effect state for certain magnetic field values. Indirect hyperfine coupling between two nuclear spins is considered as a possible mechanism of realization of a two-qubit (quantum bit) system. We study various time scales of quantum evolution. Interaction with external field causes each spin to evolve on the time scale T(ext). Spin-spin interactions result in evolution on the time scale T(int). There will be also relaxation on time scales of order T(1), and quantum decoherence/dephasing on time scales T(2). For coherent operation of a quantum computer, one needs T(1),T(2) >> T(int),T(ext). We report our recent calculations leading to estimates of T(2) and T(int), as well as survey other known results for the relevant time scales.
Thursday, October 24, 2002
Room 224 (ABB)