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University of Southern California

1. Shaw, Matthew David. Quasiparticle tunneling and quantum coherence in the single Cooper-pair box.

Degree: PhD, Physics, 2009, University of Southern California

The single Cooper-pair box (SCB) is a mesoscopic superconducting circuit which can be used to observe quantum effects. In this thesis, we attempt to improve our understanding of certain processes limiting the performance of the SCB, and work toward practical solutions. In particular, we focus on improving our understanding of nonequilibrium quasiparticle tunneling in the SCB.; We study the differential SCB (DSCB), a decoherence-avoiding symmetric SCB design which is isolated from ground, and thought to be immune from quasiparticle tunneling. However, non-equilibrium quasiparticle tunneling was still found to be quite severe in the DSCB devices. An improved readout system for multiple SCB devices, the multiplexed quantum capacitance measurement, is demonstrated experimentally and used to characterize a coupled two-qubit system. The system parameters are extracted with spectroscopy and measurements of the ground-state capacitance, and these parameters are used to estimate the ground-state concurrence, or degree of entanglement between the two SCBs.; The physics of non-equilibrium quasiparticle tunneling is explored in a system of two SCBs. Quasiparticle tunneling is measured in the time domain, and tunneling rates are extracted as a function of various system parameters, including temperature, gate voltage, RF and microwave excitation power, and magnetic field. Non-Poissonian dwell time distributions are observed and explained in terms of a kinetic theory of quasiparticle trapping. The non-equilibrium nature of the quasiparticle tunneling process is demonstrated in an elevation of the tunneling rates at low temperature, and the observed tunnel rates demonstrate quantum interference between the tunneling of electron-like and hole-like quasiparticles.; This improved understanding of quasiparticle tunneling is used to propose a new concept for an ultra-sensitive pair-breaking radiation detector, which is in principle capable of meeting the technological requirements for new experiments in far-infrared and submillimeter astrophysics. Theoretical estimates of detector performance and noise are computed for a variety of realistic design parameters. Preliminary experimental results are shown involving electrical quasiparticle injection and characterization of detector sensitivity. Advisors/Committee Members: Bozler, Hans M. (Committee Chair), Echternach, Pierre M. (Committee Member), Lu, Jia (Committee Member), Cronin, Stephen B. (Committee Member), Zanardi, Paolo (Committee Member).

Subjects/Keywords: superconducting devices; single-electron devices; quasiparticle tunneling; nonequilibrium quasiparticle dynamics; superconducting subits; suantum computation; superconducting detectors; submillimeter-wave detection; single Cooper-pair box

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Shaw, M. D. (2009). Quasiparticle tunneling and quantum coherence in the single Cooper-pair box. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/232221/rec/5364

Chicago Manual of Style (16th Edition):

Shaw, Matthew David. “Quasiparticle tunneling and quantum coherence in the single Cooper-pair box.” 2009. Doctoral Dissertation, University of Southern California. Accessed January 20, 2020. http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/232221/rec/5364.

MLA Handbook (7th Edition):

Shaw, Matthew David. “Quasiparticle tunneling and quantum coherence in the single Cooper-pair box.” 2009. Web. 20 Jan 2020.

Vancouver:

Shaw MD. Quasiparticle tunneling and quantum coherence in the single Cooper-pair box. [Internet] [Doctoral dissertation]. University of Southern California; 2009. [cited 2020 Jan 20]. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/232221/rec/5364.

Council of Science Editors:

Shaw MD. Quasiparticle tunneling and quantum coherence in the single Cooper-pair box. [Doctoral Dissertation]. University of Southern California; 2009. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/232221/rec/5364

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