Gate-tunable Josephson parametric amplifiers based on semiconductor nanowires

TL;DR

This work demonstrates gate-tunable Josephson parametric amplification using arrays of parallel InAs nanowires embedded in a microwave resonator. By increasing the number of conducting channels, the authors achieve a large $I_c$ while preserving gate tunability of the Josephson inductance, enabling resonance tuning by up to ~1 GHz and gains above 20 dB. The Kerr nonlinearity is found to be small due to high junction transparency, and the device operates as a four-wave-mixing JPA with measurable nonlinear losses and a compression point around $-137$ dBm. Noise analysis shows near-quantum-limited added noise under pump, with strong potential for on-chip integration of gate-tunable qubits and quantum-limited amplifiers on the same semiconductor-superconductor platform.

Abstract

Superconductor-semiconductor hybrid materials have been extensively used for experiments on electrically tunable quantum devices. Notably, Josephson junctions utilizing nanowire weak links have enabled a number of new gate-tunable qubits, including gatemons, Andreev level qubits and spin qubits. Conversely, superconducting parametric amplifiers based on Josephson junctions have not yet been implemented using nanowires, even though such nearly quantum limited amplifiers are key elements in experiments on quantum circuits. Here we present Josephson parametric amplifiers based on arrays of parallel InAs nanowires that feature a large critical current as required for linear amplification. The resonance frequency of the devices is gate-tunable by almost 1 GHz, with a gain exceeding 20 dB in multiple frequencies and noise approaching the quantum-limit. This new platform enables on-chip integration of gate-tunable qubits with quantum limited amplifiers using the same hybrid materials and on any substrate.

Figures (12)

• Figure 1: Elements of the nanowire-based parametric amplifier (a) Schematic of the working principle of a four-wave mixing Josephson parametric amplifier (b) False colored scanning electron micrograph of the parallel nanowire Josephson junction. Ti/Al electrodes are used to contact the nanowires on which Al has been deposited in situ after the nanowire growth. Part of the aluminum shell is chemically etched, yielding a parallel nanowire Josephson junction. Scale bar 2 $\mu$m (c) Schematic of the JPA device with a junction embedded in an Al microwave resonator. $I_{DC}$ denotes the dc current sent to junction through the dc lines. $V_g$ denotes the gate voltage applied to the Josephson junction. Inset top-left: linear equivalent circuit of the semiconducting Josephson junction. The inductance of the junction is gate tunable.
• Figure 2: Gate-tunability of the microwave resonator (a) Measured critical current with respect to the applied gate voltage on the nanowires in device JPA04 (blue) and JPA09 (red). (b) Evolution of the resonance frequency of the device with respect to the gate voltage. Effective transparency $\tau$ of the Josephson junction as a function of the gate voltage for device JPA09. (c) Internal loss rate $\kappa_i$ and (d) coupling rate $\kappa_c$ as a function of gate voltage $V_g$ for both devices.
• Figure 3: Kerr non-linearity of the resonator with nanowire Josephson junctions (a) Effect of the input power on the resonance frequency. Black arrow shows the bifurcation point at $P$ = $P_c$ (b) Magnitude of the microwave reflection with respect to frequency for various input powers $P$ at $V_g$ = 1V. Dashed lines are fits using the model described in the main text. (c) Kerr coefficient $K$ and non-linear loss rate $\kappa_{nl}$ dependence on the gate voltage, extracted by fitting $S_{11}$ at the power $P = P_c$ (All data from JPA09).
• Figure 4: Parametric amplification with the JPA (a) Magnitude of the microwave reflection $S_{11}$ from device JPA04 when the microwave pump is turned off (red line) and on (blue). (b, c) Effect of the pump frequency ($\omega_{\text{pump}}/2\pi$) and power ($P_{\text{pump}}$) on the gain ($V_g$ = -0.5 V). (d) Effect of the gate voltage on the frequency tuning of the JPA. Traces taken at various gate voltages for device JPA04 (blue) and JPA09 (red).
• Figure 5: Performances of the parametric amplifier (a) Measurement of the 1dB compression point $P_{\text{1dB}}$. Blue dashed vertical line gives $P_{\text{1dB}}$ = -137 dBm. (b) Measured power spectral density with the pump turned off (blue line) and the pump turned on (red line) (c) System added noise temperature when the JPA is off (blue trace, pump is off) and when the JPA is on(red trace, pump is on). The black dashed line is the standard quantum limit (QL = 0.15 K at this frequency) corresponds to the quantum limit. (All data from JPA09)