# Engineering of Niobium Surfaces Through Accelerated Neutral Atom Beam Technology For Quantum Applications

## TL;DR

This study introduces a room-temperature Accelerated Neutral Atom Beam (ANAB) technique to precisely engineer niobium surfaces by replacing native oxides with controlled, stable oxides, aiming to enhance qubit coherence in quantum computing.

## Contribution

The paper presents a novel application of ANAB technology for controlled surface oxide engineering on niobium, improving surface stability for quantum device performance.

## Key findings

- ANAB can produce Nb-oxide layers 2-6 nm thick.
- XPS modeling confirms controlled oxide composition and thickness.
- Surface modifications are consistent with TEM and X-ray data.

## Abstract

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLS). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by surface engineering (i.e., replacing uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages Accelerated Neutral Atom Beam (ANAB) technology at 300 mm wafer scale. This ANAB beam is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 nm to 6 nm depending on ANAB process parameters. Modeling of variable-energy XPS data confirm thickness and compositional control of the Nb surface oxide by the ANAB process. These results correlate well with those from transmission electron microscopy and X-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times.

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Source: https://tomesphere.com/paper/2302.14113