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Superconducting Nonlinear Kinetic Inductance Devices


Kher, Aditya Shreyas (2017) Superconducting Nonlinear Kinetic Inductance Devices. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9JQ0Z1F.


We describe a novel class of devices based on the nonlinearity of the kinetic inductance of a superconducting thin film. By placing a current-dependent inductance in a microwave resonator, small currents can be measured through their effect on the resonator’s frequency. By using a high-resistivity material for the film and nanowires as kinetic inductors, we can achieve a large coefficient of nonlinearity to improve device sensitivity. We demonstrate a current sensitivity of 8 pA/√Hz, making this device useful for transition-edge sensor (TES) readout and other cutting-edge applications. An advantage of these devices is their natural ability to be multiplexed in the frequency domain, enabling large detector arrays for TES-based instruments. A traveling-wave version of the device, consisting of a thin-film microwave transmission line, is also sensitive to small currents as they change the phase length of the line due to their effect on its inductance. We demonstrate a current sensitivity of 5 pA/√Hz for this version of the device, making it also suitable for TES readout as well as other current-detection applications. It has the advantage of multi-gigahertz bandwidth and greater dynamic range, offering a different approach to the resonator version of the device. Finally, we also demonstrate a transmission-line resonator version of the device that combines some of the advantages of the nanowire resonator and the traveling-wave device. This version of the device has high dynamic range but can also be easily multiplexed in the frequency domain.

A lumped-element resonator similar to the first device can be placed in a loop configuration to make it sensitive to magnetic fields. We demonstrate an example of such a device whose sensitivity could ultimately reach levels similar to those of state-of-the-art DC SQUIDs, making it potentially useful for many magnetometry applications given its ease of multiplexing. Finally, a similar microwave resonator is shown to exhibit parametric gain of up to 29 dB in the presence of a strong pump tone. The noise performance of this parametric amplifier approaches the quantum limit, making it useful for applications in quantum information and metrology.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Superconducting devices; kinetic inductance; nonlinear; current sensor; magnetometer; amplifier; transition-edge sensors
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Applied Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Zmuidzinas, Jonas
Group:Astronomy Department
Thesis Committee:
  • Zmuidzinas, Jonas (chair)
  • Schwab, Keith C.
  • Bock, James J.
  • Weinreb, Sander
Defense Date:30 August 2016
Funding AgencyGrant Number
NASA Space Technology Research FellowshipNNX12AM42H
Record Number:CaltechTHESIS:02062017-171647432
Persistent URL:
Related URLs:
URLURL TypeDescription in this paper are discussed in chapters 1-4 of the thesis
Kher, Aditya Shreyas0000-0002-5994-428X
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10047
Deposited By: Aditya Kher
Deposited On:08 Feb 2017 17:27
Last Modified:10 Mar 2020 23:25

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