Abstract
Superconducting parametric amplifiers are crucial components in microwave quantum circuits for enabling quantum-limited signal readout. The best-performing such amplifiers are often based on Josephson junctions, which however are sensitive to magnetic fields. Therefore, they require magnetic shields and are not easily integratable with other quantum systems that operate within magnetic fields, such as spin-ensemble quantum memories. To tackle this challenge, we develop a kinetic inductance-based parametric amplifier featuring a NbN nanobridge instead of Josephson junctions, which provides the desired nonlinearity for a strong parametric gain up to 42 dB. The added noise of this nanobridge kinetic-inductance parametric amplifier (hereby referred to as NKPA) is calibrated and found to be quanta for phase-preserving amplification, approaching the quantum limit of 0.5 quanta. Most importantly, we show that such excellent noise performance is preserved in an in-plane magnetic field up to 427 mT, the maximum field available in our experiment. This magnetic-field-resilient parametric amplifier presents an opportunity towards addressing single electron-spin resonance and more efficient search for axions as well as Majorana fermions.
- Received 29 September 2022
- Accepted 18 January 2023
DOI:https://doi.org/10.1103/PRXQuantum.4.010322
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
New Amplifier Works in High Magnetic Fields
Published 28 February 2023
By switching out a Josephson junction for a nanobridge, researchers have designed a new type of superconducting parametric amplifier that could work in a wider range of experiments.
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Popular Summary
State-of-the-art superconducting parametric amplifiers are a critical technology for detecting extremely weak quantum signals in superconducting quantum computers. However, the key ingredient in these amplifiers—aluminum Josephson junctions—makes them unsuitable for environments with magnetic fields. Therefore, emerging studies such as quantum memories based on electron spins and the proposed topological quantum computer are calling for a new type of magnetic-field-resilient microwave amplifier.
In this work, we demonstrate a nanobridge kinetic-inductance parametric amplifier (NKPA), designed for high-sensitivity readouts of quantum systems in the presence of strong magnetic fields. We adopt a unique nanobridge structure (with a cross section of 4 nm by 23 nm) made of niobium nitride to provide the nonlinear interaction of microwaves, allowing parametric amplification of weak signals with the minimum amount of added noise—as limited by quantum mechanics. Most importantly, with rigorous tests, we prove that such excellent performance is maintained in a magnetic field that is 10 000 times stronger than Earth’s magnetic field.
With state-of-the-art performance and magnetic-field resilience, NKPA could be the solution to quantum signal readout for various emerging and developing hybrid quantum systems.