Superconducting nanowire devices for optical quantum information processing

Baker, Luke James (2018) Superconducting nanowire devices for optical quantum information processing. PhD thesis, University of Glasgow.

Abstract

Near infrared photons are a promising choice for quantum information processing; their low transmission loss is necessary for applications such as long distance Quantum Key Distribution (QKD) in optical fibre and integrated quantum optics. An ideal proof-of-concept test of such applications would be to create, manipulate and detect single photons on a monolithic chip. Superconducting nanowire single photon detectors promise high system detection efficiencies, low dark count and low jitter under near-infrared photon illumination. Superconducting nanowire devices using NbTiN films show improved coupling efficiencies with the aid of oxidized silicon cavities. NbTiN devices were characterised in a fibre-coupled package, achieving high SDE (43%) coherent key generation rates over 200km in a T12 QKD protocol simulation. Hairpin superconducting nanowires offer excellent integration with silicon waveguide optics and can achieve near unity absorption efficiencies. Hairpin devices fabricated from MoSi films were characterised using a custom pulse tube He-3 cryostat engineered for low vibration operation at 350mK and capable of near-infrared optical maps of superconducting nanowires. The devices exhibited high critical currents 40uA), low jitter (51ps) and a dark count rate <10cps. Tests of perpendicular coupling efficiencies yield low system detection efficiencies due to high coupling losses. Using an alternative coupling method via grating couplers or cleave mounting, it is expected a much higher system detection efficiency can be achieved.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Superconductivity, nanowire, single, photon, detection, quantum, information, computing, MoSi, NbTiN, cryostat.
• Subjects: Q Science > QC Physics; T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
• Supervisor's Name: Hadfield, Professor Robert H. and Sorel, Dr. Marc
• Date of Award: 2018
• Depositing User: Mr Luke J. Baker
• Unique ID: glathesis:2018-8440
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 08 Mar 2018 09:34
• Last Modified: 10 May 2018 09:23
• URI: https://theses.gla.ac.uk/id/eprint/8440

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