Present and future of high-temperature superconductor quantum-based voltage standards

Abstract

This paper presents a brief overview of the current state-of-the-art of Josephson junctions for Quantum-based Voltage Standards fabricated with High-Temperature Superconductors (HTS). A short introduction on the history and technical evolution of Low Temperature Superconductors (LTS) technology is provided for non-specialists. Then HTS technology is summarized and discussed in the context of quantum voltage standard applications. Finally, the two most promising technologies: bicrystal and Focused Helium-Ion Beam junctions are discussed with more detail, analyzing strength, limitations and perspectives in both cases.

Recent advancements and perspectives of INRiM’s time-dependent Josephson voltage standards

“…This makes SNIS junctions potentially advantageous with respect to other technologies, facilitating the operation of PJVS arrays above 4.2 K in compact cryocoolers, in the view of the future substitution of expensive and complex LHe refrigeration systems and the consequent diffusion of voltage standards to the private companies. Indeed, present Josephson junction technologies with high temperature superconductors, like YBCO or MgB2, are not yet proven effective in providing the integration levels required for large array fabrication [17]. On the other side, the use of SNIS junctions at temperatures close to 4.2 K is favourable for the generation of wide high order steps, again thanks to the large characteristic voltages [18].…”

Advancements in quantum voltage standards for time-dependent signals

“…This makes SNIS junctions advantageous with respect to other technologies, facilitating the operation of PJVS arrays above 4.2 K in compact cryocoolers, in the view of the future substitution of expensive and complex LHe refrigeration systems and the consequent diffusion of voltage standards to the private companies. Indeed, present Josephson junctions technologies with high temperature superconductors, like YBCO or MgB 2 , are not yet proven effective in providing the integration levels required for large array fabrication [15]. On the other side, the use of SNIS junctions at temperatures close to 4.2 K is favorable for the generation of wide high order steps, again thanks to the large characteristic voltages [16].…”

Characteristics of Josephson Nb/Al/AlO$_{x}$/Nb Contacts Formed by Simplified Method

“…Надпровідникові АЦП на основі шунтованих Джозефсонових переходів SIS-типу (надпровідник-ізолятор-надпровідник), можуть працювати на частотах десятки ГігаГерц і мати значно більшу розрядність та енергоефективність [3]. З використанням Джозефсонових переходів розроблено унікальні прилади, такі як стандарти вольта [4], генератори безперервного випромінювання терагерцового діяпазону [5], [6], квантові комірки пам'яті на основі СКВІДу [7], системи квантових обчислень (кубіти) [8]. Струм крізь Джозефсонів перехід являє собою фазочутливий інструмент для визначення надпровідної симетрії параметру порядку.…”