Towards a hybrid 3D transmon qubit with topological insulator-based Josephson junctions

TL;DR

This paper reports progress in developing a hybrid 3D transmon qubit using topological insulator-based Josephson junctions, aiming to enhance quantum circuit functionalities with novel materials.

Contribution

It introduces a design for a hybrid transmon qubit with topological insulator junctions and demonstrates systematic characterization methods for device performance.

Findings

Successful fabrication of S-TI-S Josephson junctions

Comprehensive characterization of hybrid qubit devices

Identification of loss mechanisms in the system

Abstract

Superconducting quantum circuits provide a versatile platform for studying quantum materials by leveraging precise microwave control and utilizing the tools of circuit quantum electrodynamics (QED). Hybrid circuit devices incorporating novel quantum materials could also lead to new qubit functionalities, such as gate tunability and noise resilience. Here, we report experimental progress towards a transmon-like qubit made with a superconductor-topological insulator-superconductor (S-TI-S) Josephson junction using exfoliated BiSbTeSe2. We present a design that enables us to systematically characterize the hybrid device, from DC transport of the S-TI-S junction, to RF spectroscopy, to full circuit QED control and measurement of the hybrid qubit. In addition, we utilize a high-quality-factor superconducting cavity to characterize material and fabrication-induced losses, thereby guiding our efforts to improve device quality.