Nanofabrication of Superconducting Circuits, 2nd Edition

Dear Colleagues,

Superconducting circuits exhibit unique characteristics that are not attainable using conventional semiconductor electronics; these include quantum limited low noise detection and amplification, dispersion- and loss-free interconnections, as well as the energy-efficient ultra-high frequency operation of analog and digital circuits, and the realization of a scalable quantum computer. The miniaturization of superconducting circuits follows the trend of the miniaturization of semiconductor electronics, but with significant delay and specificity related to the spatial variations in the macroscopic wave function of phase-correlated Cooper pairs in superconductors. In contrast to semiconductors and normal metals, for example, a nanometer-sized constriction transforms superconductors into a Josephson junction, which serves as an active component of superconductor electronics. Today's superconducting components must be manufactured on scales comparable to, or even smaller than, the superconducting coherence length and London penetration depth, which creates difficulties in the manufacturing, operation, and theoretical interpretation of the properties of the devices (the coherence length and the penetration depth depend on the local lateral dimensions of the superconducting structures).

The need to develop specific methods for nanofabrication, to minimize or exploit the kinetic inductance of ultra-thin superconducting structures, and the need to squeeze a quantum of magnetic flux into nanoscale superconducting cells with Josephson junctions are some of the main obstacles in the miniaturization of superconducting circuits. They should be addressed in a comprehensive manner for specific applications.

The most popular superconducting materials that are used in superconducting electronics are Nb, Al, NbN, NbTiN, TiN, MoRe, and YBa₂Cu₃O_7-x. Electron beam lithography, direct writing via laser, focused ion beam milling, and self-aligned nanofabrication are the most frequently used methods for the creation of nanoscale superconducting devices. Superconducting bolometers, single photon detectors, SIS detectors, Josephson junctions, SQUIDs, RSFQ circuits, qubits, and their readouts are just some of the established applications of superconducting circuits that require fabrication with nanometer resolutions.

The objective of this Special Issue is to present studies in the field of nanoscale superconducting devices, with emphasis on their nanofabrication, testing, and theoretical modeling. Therefore, researchers are invited to submit their manuscripts to this Special Issue and contribute their theoretical models, technological developments, reviews, and studies.

Prof. Dr. Michael I. Faley
Guest Editor

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• nanostructuring
• Josephson junctions
• SQUIDs
• superconducting single photon detectors
• SIS detectors
• superconducting bolometers
• qubits

• Nanofabrication of Superconducting Circuits in Electronics (6 articles)