Seminar: Development of superconductor-semiconductor nanowires

Dr. Moira Hocevar will give a seminar on “Development of superconductor-semiconductor nanowires for quantum circuits”

Moira is a research scientist at Institut Néel Grenoble, France: http://perso.neel.cnrs.fr/moira.hocevar/my-research.html

Abstract:

The epitaxy community is making significant advances in high-quality superconductor-semiconductor hybrids. These heterostructures hold promise for enabling error-limited quantum computation through qubits with longer coherence times, as well as topologically protected qubits. This effort began with the quest for improved material interfaces for gate tunable Josephson junctions, such as optimized Al/InAs and Al interfaces. However, aluminum is limited in terms of critical current, and many other superconductors remain underexplored. 

Here, we present our efforts to develop expertise in large supercurrent nanowire Josephson junctions either by using parallel Al/InAs nanowires or by using an alternative superconductor such as tin (Sn). Tin is known for having higher critical temperatures (Tc​) and higher superconducting gap than aluminum. However, it is an allotrope, meaning it can exist in multiple crystalline phases, with only one phase being suitable for quantum bit technologies. Therefore, significant work is needed to control the crystalline phase of Sn during epitaxy or deposition to favor the desired phase [1,2]. Additionally, it is critical to ensure that interfaces remain undamaged during the growth process. 

Both our strategies show large improvement and tunability of the critical current. In the case of Sn/InAs nanowires, the devices show additionally strong resilience to magnetic fields [3]. Tunable and large critical currents as well as magnetic field resilience are essential properties for quantum devices. Preliminary measurements of Josephson parametric amplifiers and gatemon qubits will be presented.

References: 

[1] M. Pendharkar et al, Science (2021) 

[2] A. H. Chen et al, Nanotechnology (2023)

[3] A. Sharma et al, in preparation (2025)