Superconducting single photon detectors for quantum information processing

Kirkwood, Robert A. (2017) Superconducting single photon detectors for quantum information processing. PhD thesis, University of Glasgow.

Abstract

Single photon detectors are a vital part of many emerging technologies which harness the quantum properties of light to benefit the fields of communication, computation and sensing. Superconducting nanowire single photon detectors (SNSPDs) offer high detection efficiency, low dark count rates, low timing jitter, and infrared sensitivity that are required by the most demanding single photon counting applications. This thesis presents SNSPDs fabricated and tested at the University of Glasgow that are integrated with optical structures which enable enhanced detection efficiency and integration with waveguide circuit technology. The monolithic integration of waveguide circuit components presents a route towards realisation of an optical quantum information processor that has the stability and scalability to perform the demanding tasks of quantum computation. A novel process is introduced for incorporating superconducting detectors with single mode gallium arsenide waveguides and quantum dot single photon sources. Together these elements would enable the generation of quantum states of light which could be manipulated and detected on a single chip. Detectors are patterned in NbTiN thin superconducting films on to suspended nanobeam waveguides with better than 50 nm alignment accuracy. Low temperature electrical and optical testing confirms the detectors’ single photon sensitivity under direct illumination as well as to waveguide coupled light. Measured detectors were found to have internal registering efficiencies of 6.8 ± 2.4%. Enhancing absorption of photons into thin superconducting films is vital to the creation of high efficiency superconducting single photon detectors. Fabricating an SNSPD on a dielectric mirror creates a partial cavity that can be tailored to enhance detection of light at specific wavelengths. Devices have been fabricated and tested in this thesis with enhanced detection efficiency at infrared and visible wavelengths for quantum cryptography, remote sensing and life science applications. Detectors fabricated in NbTiN on GaAs/AlGaAs Bragg mirrors exhibited a system detection efficiency of 1.5% at 1500 nm wavelength for the best device measured. SNSPDs were also fabricated in NbN on aperiodic dielectric mirrors with a range of different bandwidths. A peak system detection efficiency of 82.7% at 808 nm wavelength was recorded.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Superconducting nanowire single photon detector, integrated photonics, quantum information.
• Subjects: Q Science > QC Physics; T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Supervisor's Name: Hadfield, Professor Robert H.
• Date of Award: 2017
• Depositing User: Dr Robert Kirkwood
• Unique ID: glathesis:2017-8136
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 May 2017 15:54
• Last Modified: 04 Apr 2019 09:49
• URI: https://theses.gla.ac.uk/id/eprint/8136