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Khalifa, Mohammad

University of British Columbia

Superconducting circuits are used for processing quantum signals carried by microwave photons. These circuits comprise two types of nonlinear resonant devices. First, strongly nonlinear qubits are used for processing quantum information. Second, weakly nonlinear parametric amplifiers (PAs) are used for low-noise amplification and squeezing. The nonlinearity is mostly realized by explicitly defined Al/AlOx Josephson junctions (JJs), with long arrays of large JJs for weak nonlinearity and a single or a few small JJs for strong nonlinearity. Recently, there has been an increasing interest in devices made of strongly disordered superconducting materials possessing nonlinear kinetic inductance (KI). These devices act effectively as arrays of JJs, which simplifies the fabrication of weakly nonlinear devices compared to the explicit arrays of JJs. Although understanding the performance of the KI devices as PAs is still underway, they hold promise for some desirable features, including higher power handling, elevated temperature operation, and magnetic field resilience. The latest feature is necessary for the applications requiring high magnetic field, including spin-based quantum computing, which could ultimately be more scalable than superconducting quantum systems due to small, coherent qubits. This thesis makes progress towards understanding and developing KIPAs based on highly disordered, nonlinear superconducting nanowire resonators. First, the performance of KIPAs made of thin NbTiN films is studied at high magnetic fields. The nonlinearity of KI resonators is measured for nanowires with different widths at zero and high magnetic fields, verifying the small nonlinearity necessary for high power handling. The performance of these nanowires is then investigated as KIPAs for in-plane magnetic fields up to 2 Tesla, demonstrating the robustness of narrower designs to high magnetic field. Second, a new variant of the KIPA, the kinetic inductance parametric converter (KIPC), is proposed, demonstrated, and analyzed. The KIPC is an intrinsically nondegenerate parametric device that is capable of coherent two-mode parametric amplification or frequency conversion. It utilizes DC current bias and provides higher power handling compared to its JJ-based counterpart. These results represent a step in the pathway of transferring the JJ-based parametric amplification technology into a KI platform that is more versatile and compatible with other quantum systems.

Text

2024-08-30

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89116

Electrical and Computer Engineering

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/