A promising proposal for quantum computation, due to Loss and DiVincenzo, is based on using electron spins in quantum dots as qubits - two-level systems which are the quantum analogues of classical bits. Two-qubit operations (quantum gates) are then carried out by switching on and off the exchange interaction between neighboring spins (i.e. "pulsing" the interaction). This thesis presents a study of the effect of anisotropic corrections to the exchange interaction due to spin-orbit coupling on this scheme. It is shown that time-symmetric pulsing automatically eliminates some undesirable terms in the resulting quantum gates, and well-chosen pulse shapes can produce an effectively isotropic exchange gate which can be used for universal quantum computation. Deviations from perfect time-symmetric pulsing are then studied in the context of a microscopic model of GaAs quantum dots. A new proposal for universal quantum computation which uses control of anisotropic corrections is then presented. In this proposal, the number of pulses required to carry out quantum gates scales as the inverse of a dimensionless measure of the degree of control. The size of this dimensionless figure-of-merit" depends on (i) variation of anisotropy with interdot distance, and (ii) restrictions on the pulse duration due to decoherence for slow pulses and nonadiabatic transitions for fast pulses. Taking these constraints into account, the figure-of-merit is estimated for GaAs quantum dots and shown to be large enough to be useful forquantum computation. / A Dissertation submitted to the Department of Physics in partial fulfillment of the
requirements for the degree of Doctor of Philosophy. / Degree Awarded: Summer Semester, 2005. / Date of Defense: June 10, 2005. / Spin-orbit coupling, Quantum dots, Quantum computing / Includes bibliographical references. / Nicholas E. Bonesteel, Professor Directing Thesis; Washington Mio, Outside Committee Member; Vladimir Dobrosavljevi´c, Committee Member; Stephan von Molnar, Committee Member; Mark Riley, Committee Member.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_168506 |
| Contributors | Stepanenko, Dimitrije (authoraut), Bonesteel, Nicholas E. (professor directing thesis), Mio, Washington (outside committee member), Dobrosavljevi´c, Vladimir (committee member), Molnar, Stephan von (committee member), Riley, Mark (committee member), Department of Physics (degree granting department), Florida State University (degree granting institution) |
| Publisher | Florida State University |
| Source Sets | Florida State University |
| Language | English, English |
| Detected Language | English |
| Type | Text, text |
| Format | 1 online resource, computer, application/pdf |
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