Qubit dynamics under alternating controls
Name
899983870-MIT.pdf
Description
Full printable version
Size
11.5 MB
Format
Adobe PDF
Checksum (MD5)
e67c8cbc98a5443f6454dd9ee3f6b8d1
Author(s)
Aiello, Clarice Demarchi
Advisor(s)
Paola Cappellaro.
Date Issued
2014
Publisher
Massachusetts Institute of Technology
Abstract
In this thesis, we discuss two problems of quantum dynamics in the presence of alternating controls. Alternating controls arise in many protocols designed to extend the duration over which a qubit is a useful computational resource. This is accomplished by control sequences that either retard decoherence, or that accomplish a quantum operation in as short a time as possible. The first problem tackles the use of a composite-pulse control sequence known as 'rotary-echo' for quantum magnetometry purposes. The sequence consists in the continuous drive of a qubit, with field phases that alternate at specific intervals. We implement such a magnetometry protocol using an electronic qubit in diamond, and experimentally confirm the flexibility yielded by the tuning of sequence parameters that achieves a good compromise between decoherence resilience and sensitivity. The second problem theoretically investigates the time-optimal evolution of a qubit in the case of a restricted control set composed of alternating rotations around two non-parallel axes on the Bloch sphere. Using accessible algebraic methods, we show that experimental parameters, such as the angle between the two rotation axes, restrict the necessary structure of time-optimal sequences. We propose to implement such an evolution through alternate driving as an advantageous alternative to the slow, noisy direct addressing of a nuclear qubit anisotropically hyperfine-coupled to an electronic spin in diamond.
Description
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 111-117).
Subjects
Electrical Engineering and Computer Science.
MIT Department
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
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