Controlling open quantum systems

This thesis describes the development and experimental verification (via liquid state nuclear magnetic resonance techniques) of new methods for controlling open quantum systems. First, methods that improve coherent control through the use of both strong control fields and detailed knowledge of the system's Hamiltonian are demonstrated. With the aid of numerical search methods, pulsed irradiation schemes are obtained that perform accurate, arbitrary, selective gates on multi-qubit systems. For a 3-qubit system, implementations show that the control sequences faithfully implement unitary operations with simulated gate fidelities on the order of 0.999 and experimentally determined projections of 0.99. Next, methods for controlling a quantum information in the presence of collective phase noise is demonstrated through the use of a decoherence free subspace (DFS). In addition to demonstrating the robustness of the DFS memory for both engineered and natural noise processes, a universal set of logical manipulations over the encoded qubit is realized. Dynamical control methods at the encoded level are used to implement noise-tolerant control over the DFS qubit in the presence of engineered phase noise significantly stronger than observed from natural noise sources.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Nuclear Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2002

Author dc:creator

• Fortunato, Evan Matthew

Advisor dc:contributor.advisor

• David G. Cory.

• Nuclear Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/17652

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/17652