Abstract
A microwave amplifier combining noise performances as close as possible to the quantum limit with large bandwidth and high saturation power is highly desirable for many solid-state quantum technologies. Here, we introduce a new traveling-wave parametric amplifier based on superconducting quantum interference devices. It displays a 3-GHz bandwidth, a -dBm saturation (1-dB compression) point and added noise near the quantum limit. Compared to the previous state of the art, it is an order of magnitude more compact, its characteristic impedance is in situ tunable, and its fabrication process requires only two lithography steps. The key is the engineering of a gap in the dispersion relation of the transmission line. This is obtained using a periodic modulation of the SQUID size, similarly to what is done with photonic crystals. Moreover, we provide a new theoretical treatment to describe the nontrivial interplay between nonlinearity and such periodicity. Our approach provides a path to cointegration with other quantum devices such as qubits given the low footprint and easy fabrication of our amplifier.
- Received 20 September 2019
- Revised 4 January 2020
- Accepted 3 March 2020
DOI:https://doi.org/10.1103/PhysRevX.10.021021
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
synopsis
synopsisA Simple Solution for Microwave Amplification
Published 28 April 2020
A new solution to the phase-matching problem common to so-called traveling-wave parametric amplifiers is achieved with a simple design that’s easy to fabricate.
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Popular Summary
Most solid-state quantum technologies rely on the ability to measure very weak microwave signals at cryogenic temperatures. Recording these signals requires quantum-limited amplifiers, which have the lowest intrinsic noise allowed by quantum mechanics. Today, state-of-the-art amplifiers combine thousands of Josephson junctions (pairs of weakly connected superconducting layers) in an array to provide traveling-wave amplification. However, such architectures remain hard to implement, in particular, because of a so-called phase-matching issue. We demonstrate experimentally a new, simple, efficient design to overcome this problem.
In order to achieve high gain, the phase between the signal to be amplified and the pump that provides energy to the system must be constantly matched while both propagate into the device. Given the nonlinear nature of the Josephson-junction array, their wave velocity is not the same, therefore inducing a phase mismatch. We engineer the dispersion relation of this array by periodically modulating the impedance of the medium, as is usually done with photonic crystals. This local distortion in the dispersion slows down the pump wave and matches it with the signal.
Our design drastically reduces the fabrication complexity of quantum-limited amplifiers based on traveling-wave architectures. It allows their fabrication in academic laboratories, a prerequisite to solving outstanding problems and to unleashing the full potential of such amplifiers. Furthermore, the architecture we propose is a first step toward an on-chip integration of Josephson traveling-wave amplifiers with superconducting qubits, which would represent a big leap forward for quantum technologies.
