Andreev Interferometry of Flux Qubits Driven By Radio Frequency Field

Chris Checkley

Research output: ThesisDoctoral Thesis

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In this thesis we present the continuing work done examining a system in
which an Andreev interferometer is used to probe the state of a flux qubit.
In particular, we show that the back action of the interferometer on the
qubit is low enough that an energy gap can still be observed in the qubit,
and present the first experimental evidence of resonant excitation of a flux
qubit detected using an Andreev interferometer.
We begin by discussing the theory of flux qubits and Andreev interferometers
individually. We then go on to examine what happens when with
these two types of structures are combined, with particular attention being
paid to the consequences for the coherence time of the qubit.
We then discuss the practical elements of the experiment, notably the
development of a tri-layer resists system that can be used to create high
quality mesoscopic structures.
We present the experimental results, which show the evidence for resonant
excitation of a qubit detected using an Andreev interferometer. The quality
of these resonances suggests that the system has a coherence time of less
than 1ns.
To conclude we examine some ways in which we believe the system can
be improved in order to allow more detailed spectroscopic and time resolved
Original languageEnglish
Awarding Institution
  • Royal Holloway, University of London
  • Petrashov, Victor, Supervisor
Thesis sponsors
Award date1 Apr 2010
Publication statusUnpublished - 2009

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