Gate tunability and nonlinearity in hybrid superconductor-semiconductor resonators
Doctoral thesis, 2026
Superconducting microwave resonators and Josephson elements form the basis of a broad range of quantum information technologies, including circuit quantum electrodynamics, Josephson parametric amplification, bosonic quantum computing, and engineered interactions between microwave modes. The properties of these circuits are largely determined by material parameters and design geometry, while magnetic flux often provides a means of in situ control. Electrostatic gating offers an additional degree of freedom, motivating the investigation of gate-tunable superconducting circuits, particularly through the integration of superconductors with semiconductor elements.
In this thesis, we investigate the gate tunability and nonlinear response of superconducting microwave resonators incorporating indium arsenide (InAs) nanowires with epitaxial aluminum (Al) shells. We explore two distinct forms of gate control in this platform: the modification of the superconducting properties of the Al shell and the electrostatic tuning of Andreev bound states (ABSs) in Josephson weak links defined in the InAs core.
We characterize the first form of gate control by measuring the gate-induced changes in resonator frequency and internal losses. We demonstrate that the observed response is well described by the Mattis--Bardeen model using an effective-temperature approach, consistent with an increase in quasiparticle population. Time-domain and modulation measurements further reveal characteristic response times down to a few tens of nanoseconds, highlighting the potential of this mechanism for applications in cryogenic switching and superconducting electronics.
We then investigate the ABS--resonator interaction in both the linear and nonlinear regimes, demonstrating coupling strengths approaching the ultrastrong-coupling regime and, most notably, gate and flux control over the ABS-induced Kerr and cubic nonlinearities. In particular, we show that the Kerr contribution can be tuned through zero while maintaining a finite cubic nonlinearity, and observe three-wave-mixing parametric amplification. These findings are particularly relevant for applications requiring three-wave mixing with suppressed Kerr effects, such as Josephson parametric amplification.
Together, these results demonstrate the potential of hybrid superconductor--semiconductor devices for engineering gate-tunable microwave circuits and controlling their linear and nonlinear response.
In this thesis, we investigate the gate tunability and nonlinear response of superconducting microwave resonators incorporating indium arsenide (InAs) nanowires with epitaxial aluminum (Al) shells. We explore two distinct forms of gate control in this platform: the modification of the superconducting properties of the Al shell and the electrostatic tuning of Andreev bound states (ABSs) in Josephson weak links defined in the InAs core.
We characterize the first form of gate control by measuring the gate-induced changes in resonator frequency and internal losses. We demonstrate that the observed response is well described by the Mattis--Bardeen model using an effective-temperature approach, consistent with an increase in quasiparticle population. Time-domain and modulation measurements further reveal characteristic response times down to a few tens of nanoseconds, highlighting the potential of this mechanism for applications in cryogenic switching and superconducting electronics.
We then investigate the ABS--resonator interaction in both the linear and nonlinear regimes, demonstrating coupling strengths approaching the ultrastrong-coupling regime and, most notably, gate and flux control over the ABS-induced Kerr and cubic nonlinearities. In particular, we show that the Kerr contribution can be tuned through zero while maintaining a finite cubic nonlinearity, and observe three-wave-mixing parametric amplification. These findings are particularly relevant for applications requiring three-wave mixing with suppressed Kerr effects, such as Josephson parametric amplification.
Together, these results demonstrate the potential of hybrid superconductor--semiconductor devices for engineering gate-tunable microwave circuits and controlling their linear and nonlinear response.
gate-tunability
InAs nanowires
cubic nonlinearity
Kerr nonlinearity
Superconducting resonators
Josephson junctions
Author
Vittorio Buccheri
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Device Physics
Superconducting circuits are among the key building blocks of emerging quantum technologies, including quantum computing. Operating at temperatures close to absolute zero, they can store and manipulate information encoded in microwave signals with very little energy loss. Many of their properties depend on the choice of materials and circuit geometry, while real-time fine-tuning is most commonly achieved using small magnetic fields.
This thesis explores an additional way to control superconducting circuits: electrostatic gating, much like conventional CMOS-based electronics. To investigate this approach, we combine superconducting resonators with semiconductor nanowires made of indium arsenide and coated with a thin superconducting aluminium shell.
We investigate two distinct forms of gate control. In the first, an applied voltage modifies the superconducting properties of the aluminium shell. In the second, voltage controls quantum states known as Andreev bound states, confined within narrow sections of the nanowire.
By studying both forms of gate control at microwave frequencies, we show how voltage can tune the resonator response. In particular, we characterize changes in resonator frequency and energy losses, and demonstrate control over nonlinear effects that can be used, among other applications, for parametric amplification.
Together, these results show how combining superconductors and semiconductors opens new possibilities for controlling microwave signals and designing tunable circuits for quantum technologies.
This thesis explores an additional way to control superconducting circuits: electrostatic gating, much like conventional CMOS-based electronics. To investigate this approach, we combine superconducting resonators with semiconductor nanowires made of indium arsenide and coated with a thin superconducting aluminium shell.
We investigate two distinct forms of gate control. In the first, an applied voltage modifies the superconducting properties of the aluminium shell. In the second, voltage controls quantum states known as Andreev bound states, confined within narrow sections of the nanowire.
By studying both forms of gate control at microwave frequencies, we show how voltage can tune the resonator response. In particular, we characterize changes in resonator frequency and energy losses, and demonstrate control over nonlinear effects that can be used, among other applications, for parametric amplification.
Together, these results show how combining superconductors and semiconductors opens new possibilities for controlling microwave signals and designing tunable circuits for quantum technologies.
Andreev qubits for scalable quantum computation (AndQC)
European Commission (EC) (EC/H2020/828948), 2019-09-01 -- 2023-03-31.
Areas of Advance
Nanoscience and Nanotechnology
Subject Categories (SSIF 2025)
Condensed Matter Physics
Other Physics Topics
Infrastructure
Myfab (incl. Nanofabrication Laboratory)
DOI
10.63959/chalmers.dt/5969
ISBN
978-91-8103-512-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5969
Publisher
Chalmers
Kollektorn, Kemivägen 9, Chalmers.
Opponent: Research Director Silvano De Franceschi, Interdisciplinary Research Institute of Grenoble, France