[Paper Review] Integration of selectively grown topological insulator nanoribbons in superconducting quantum circuits

Tobias Schmitt, M. R. Connolly+16 more|arXiv (Cornell University)|Jul 8, 2020

Topological Materials and Phenomena4 citations

TL;DR

This paper demonstrates the integration of nanoscale topological insulator nanoribbons into mm-scale superconducting quantum circuits using selective area epitaxy and local stencil lithography. The technique enables on-chip microwave cavities coupled to topological insulator-shunted qubits, revealing nonlinear qubit behavior and confirming compatibility with superconducting microwave applications.

ABSTRACT

We report on the precise integration of nm-scale topological insulator Josephson junctions into mm-scale superconducting quantum circuits via selective area epitaxy and local stencil lithography. By studying dielectric losses of superconducting microwave resonators fabricated on top of our selective area growth mask, we verify the compatibility of this in situ technique with microwave applications. We probe the microwave response of on-chip microwave cavities coupled to topological insulator-shunted superconducting qubit devices and observe a power dependence that indicates nonlinear qubit behaviour. Our method enables integration of complex networks of topological insulator nanostructures into superconducting circuits, paving the way for both novel voltage-controlled Josephson and topological qubits.

Motivation & Objective

• To develop a scalable method for integrating topological insulator nanostructures into superconducting quantum circuits.
• To enable precise placement of nm-scale topological insulator Josephson junctions within mm-scale quantum devices.
• To verify compatibility of the integration technique with superconducting microwave applications through dielectric loss measurements.
• To probe nonlinear microwave responses in on-chip cavities coupled to topological insulator-shunted qubits.
• To pave the way for complex networks of topological insulator-based qubits in superconducting quantum architectures.

Proposed method

• Selective area epitaxy is used to grow topological insulator nanoribbons with atomic precision on a predefined mask.
• Local stencil lithography enables precise positioning of the nanoribbons relative to superconducting circuit components.
• Dielectric loss measurements are performed on microwave resonators fabricated on the growth mask to assess material compatibility.
• On-chip microwave cavities are coupled to topological insulator-shunted superconducting qubits for microwave response characterization.
• Power-dependent microwave response is measured to probe nonlinear behavior in the qubit system.
• The integration process is in situ, preserving material integrity and enabling direct coupling to quantum circuits.

Experimental results

Research questions

• RQ1 Can topological insulator nanoribbons be precisely integrated into mm-scale superconducting quantum circuits using scalable fabrication techniques?
• RQ2 What is the microwave compatibility of the selective area growth mask used in the integration process?
• RQ3 How does the microwave response of on-chip cavities coupled to topological insulator-shunted qubits behave under varying power levels?
• RQ4 Can the integration method support the formation of complex networks of topological insulator nanostructures in superconducting circuits?
• RQ5 What evidence supports the feasibility of voltage-controlled Josephson and topological qubits using this approach?

Key findings

• Dielectric loss measurements on resonators fabricated on the growth mask confirm the compatibility of the selective area epitaxy technique with superconducting microwave applications.
• A power-dependent microwave response is observed in on-chip cavities coupled to topological insulator-shunted qubits, indicating nonlinear qubit behavior.
• The integration method enables precise placement of nm-scale topological insulator Josephson junctions within superconducting circuits.
• The in situ fabrication process preserves material quality and supports direct coupling to quantum devices.
• The approach opens a pathway for realizing voltage-controlled Josephson and topological qubits in scalable superconducting quantum circuits.
• The technique is scalable and suitable for constructing complex networks of topological insulator nanostructures in quantum circuits.