Ultrahigh Vacuum Packaging and Surface Cleaning for Quantum Devices

TL;DR

This paper presents an ultra-high vacuum packaging system for quantum devices that enables surface treatments and maintains vacuum during cooling, leading to improved qubit coherence times.

Contribution

It introduces a novel UHV package design with integrated surface treatment capabilities and active vacuum maintenance during cryogenic cooling.

Findings

Achieved average T₁ of 84 μs for flux-tunable qubits.

Achieved T₂ echo of 134 μs after vacuum loading.

Demonstrated effective vacuum retention during cooling process.

Abstract

We describe design, implementation and performance of an ultra-high vacuum (UHV) package for superconducting qubit chips or other surface sensitive quantum devices. The UHV loading procedure allows for annealing, ultra-violet light irradiation, ion milling and surface passivation of quantum devices before sealing them into a measurement package. The package retains vacuum during the transfer to cryogenic temperatures by active pumping with a titanium getter layer. We characterize the treatment capabilities of the system and present measurements of flux tunable qubits with an average T$_1=84~\mu$s and T$^{echo}_2=134~\mu$s after vacuum-loading these samples into a bottom loading dilution refrigerator in the UHV-package.