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Probing Oxidation-Driven Amorphized Surfaces in a Ta(110) Film for Superconducting Qubit
Junsik Mun1,2, Peter V Sushko3, Emma Brass2
1Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States.
ACS Nano
|December 26, 2023
Summary
Surface oxidation in tantalum (Ta) films is a key factor limiting superconducting qubit coherence. Understanding this atomic-scale process is crucial for developing advanced quantum computing hardware.
Area of Science:
- Quantum Computing
- Materials Science
- Surface Science
Background:
- Superconducting qubits are essential for quantum computing.
- Tantalum (Ta)-based qubits show promise but are limited by coherence times.
- Uncontrolled surface oxidation is a suspected cause of energy loss in transmon qubits.
Purpose of the Study:
- To investigate the atomic-scale surface oxidation mechanism of native Ta films.
- To understand the impact of oxidation on superconducting qubit lifetime.
- To provide insights for improving quantum processor performance.
Main Methods:
- Advanced scanning transmission electron microscopy (STEM).
- Density functional theory (DFT) calculations.
- Atomistic modeling of oxidized Ta(110) surfaces.
Main Results:
- Oxygen penetrates Ta surfaces, accumulating between atomic planes.
- High oxygen concentration (>1:1 O/Ta ratio) leads to amorphous Ta₂O₅ formation.
- A noninsulating TaO₁-δ suboxide layer contributes to qubit losses via charge redistribution and polarization.
Conclusions:
- Subsurface oxidation impacts qubit coherence through quasiparticle loss and reduced current capacity.
- Findings clarify realistic factors affecting superconducting qubit performance.
- Provides guidance for the development of future quantum computing hardware.
