26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Seven Magnets, One Dilution Fridge: Compact Superconducting Magnets for Quantum Science

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Poster AIP | Condensed Matter & Materials (CMM)

Speaker

Dr Timothy Newman (The Little Magnet Company)

Description

Superconducting magnets are essential for many solid-state quantum research efforts, but conventional systems impose significant constraints on experiments. They occupy the majority of the available experimental volume of a dilution refrigerator, increase the time taken to cool and warm a cryostat, and limit a fridge to a single magnet — and therefore a single experiment — at a time. Traditional superconducting magnets provide high field homogeneity over many cubic centimetres of volume, something which is no longer required for the nanoscale electronic and photonic devices that are being tested today. As experimental groups grow, device throughput is often bottlenecked by access to magnets.
We present a suite of compact superconducting magnet systems. These magnets have been designed specifically for integration into cryogen-free dilution refrigerators. They are small enough to mount directly at the mixing chamber stage, and are monolithically integrated with the device under test, reducing the sensitivity to vibrations – usually caused by pendulum-mode effects observed in ‘cold-finger’ configurations.
We report the operation of seven superconducting electromagnets running simultaneously in a single Bluefors LD250 dilution refrigerator, enabling concurrent magnetically-tuned experiments in one cooldown. Individual solenoids have demonstrated fields of 2.1 T, and a two-axis vector magnet system has enabled rotations at 350 mT.
We discuss the design considerations for our compact magnets — heat loads, quench management, field homogeneity over device-scale volumes — and present measured performance data and numeric simulations of these parameters. We discuss our next steps: improved ease-of-integration, persistent-mode operation, and development of general-purpose mounts for exchange-gas and liquid-cooled systems.
Our magnets were developed by researchers in rare-earth-ion quantum labs, motivated by the constraints of our own experiments. We outline application examples in spin-qubit characterisation, vector magnetometry of systems with anisotropic g-tensors, and multiplexed cryogenic device screening.