Romans, Edward;
Meti, Laith;
Hao, Ling;
Gallop, John;
Shaforost, Olena;
Potter, Jamie;
Chapman, Gemma;
(2024)
Towards a near quantum-limited planar SLUG amplifier at microwave frequencies.
IEEE Transactions on Applied Superconductivity
(In press).
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Abstract
The Superconducting Low-inductance Undulatory Galvonometer (SLUG) microwave amplifier is distinct from a conventional SQUID amplifier in that the signal to be amplified is directly injected into the SQUID loop, allowing high frequency operation. Here, we discuss a planar SLUG amplifier constructed with nanobridge weak-links fabricated from a single niobium layer. DC characterisation of the SLUG gain element is presented for two nanobridge fabrication techniques. Measurements show that junctions fabricated from Ne focused-ion-beam, and from 100 keV electron-beam lithography, have significantly different DC characteristics with critical currents on the order of 100 µA and 1 mA respectively. Both variants exhibit maximum forward transfer functions greater than 1.5 mV/Φ0, which is larger than those reported in Nb SIS-junction SLUGs. Theoretical modelling has shown that an amplifier containing a planar, nanobridge SLUG as a gain element is expected to exhibit gain exceeding 15 dB with large instantaneous bandwidth, and can be designed to operate well in excess of 20 GHz.
| Type: | Article |
|---|---|
| Title: | Towards a near quantum-limited planar SLUG amplifier at microwave frequencies |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | The authors would like to thank the UK Science and Technology Facilities Council (STFC) for funding this work through support for the Quantum Sensors for the Hidden Sector (QSHS) and Quantum Technologies for Neutrino Mass (QTNM) collaborations under grants ST/T006064/1 and ST/T006137/1. Further acknowledgement and thanks are given to the National Metrology Institute, Beijing, China for providing the niobium films. For the purpose of open access, the authors have applied a Creative Commons Attribution (CC BY) license to any Accepted Manuscript version arising. |
| Keywords: | Low-noise amplifier, Superconducting lowinductance undulatory galvonometer (SLUG), Nanobridge, Electron-beam lithography (EBL), Focused-ion-beam (FIB) |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Electronic and Electrical Eng |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10182361 |
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