Dissertation/Thesis Abstract

Controlling coherent state superpositions with superconducting circuits
by Vlastakis, Brian Michael, Ph.D., Yale University, 2015, 241; 10013061
Abstract (Summary)

Quantum computation requires a large yet controllable Hilbert space. While many implementations use discrete quantum variables such as the energy states of a two-level system to encode quantum information, continuous variables could allow access to a larger computational space while minimizing the amount of re- quired hardware. With a toolset of conditional qubit-photon logic, we encode quantum information into the amplitude and phase of coherent state superpositions in a resonator, also known as Schrddinger cat states. We achieve this using a superconducting transmon qubit with a strong off-resonant coupling to a waveguide cavity. This dispersive interaction is much greater than decoherence rates and higher-order nonlinearites and therefore allows for simultaneous control of over one hundred photons. Furthermore, we combine this experiment with fast, high-fidelity qubit state readout to perform composite qubit-cavity state tomography and detect entanglement between a physical qubit and a cat-state encoded qubit. These results have promising applications for redundant encoding in a cavity state and ultimately quantum error correction with superconducting circuits.

Indexing (document details)
Advisor: Schoelkopf, Robert J.
School: Yale University
School Location: United States -- Connecticut
Source: DAI-B 77/06(E), Dissertation Abstracts International
Subjects: Physics
Keywords: Cavity Quantum Electrodynamics, Quantum Computing, Quantum Information, Quantum Optics, Superconducting Qubits
Publication Number: 10013061
ISBN: 978-1-339-47834-0
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