Bespoke magnetic field design for a magnetically shielded cold atom interferometer

Abstract

Quantum sensors based on cold atoms are being developed which produce measurements of unprecedented accuracy. Due to shifts in atomic energy levels, quantum sensors often have stringent requirements on their internal magnetic field environment. Typically, background magnetic fields are attenuated using high permeability magnetic shielding, with the cancelling of residual and introduction of quantisation fields implemented with coils inside the shield. The high permeability shield, however, distorts all magnetic fields, including those generated inside the sensor. Here, we demonstrate a solution by designing multiple coils overlaid on a 3D-printed former to generate three uniform and three constant linear gradient magnetic fields inside the capped cylindrical magnetic shield of a cold atom interferometer. The fields are characterised in-situ and match their desired forms to high accuracy. For example, the uniform transverse field, Bx, deviates by less than 0.2% over more than 40% of the length of the shield. We also map the field directly using the cold atoms and investigate the potential of the coil system to reduce bias from the quadratic Zeeman effect. This coil design technology enables targeted field compensation over large spatial volumes and has the potential to reduce systematic shifts and noise in numerous cold atom systems.

Enabling ambulatory movement in wearable magnetoencephalography with matrix coil active magnetic shielding

“…The matrix coils, the method of production of spherical harmonic fields and the shielding framework adopted here could also have application outside MEG. For example, in designing excitation fields for large magnetic induction tomography systems ( Cubero et al, 2020 ; Kim et al, 2019 ); adaptive nulling for atom interferometers for gravity sensing ( Hobson et al, 2022 ); reducing systematic errors as mobile atom interferometers are deployed in real-world environments ( Wu et al, 2019 ) and for fundamental physics experiments including very long baseline atom interferometry ( Wodey et al, 2020 ) and measurements of the electric dipole moment of the neutron ( Afach et al, 2014 ).…”

A gravitational eye: a method for extracting maximum information from gravitational potentials

“…In addition to keeping the atom cloud within the interferometry beam, there are a number of systematic effects which would need to be addressed to prevent a reduction in sensitivity or a bias. Possible sources of bias include the Coriolis effect, contrast loss and phase shifts due to passing at an angle through the interferometry beam, self-gravitation and the Quadratic Zeeman effect [77]. There are currently a number of methods used or in deployment to deal with these systematic effects which could be implemented in a gravitational eye [78][79][80][81].…”

Magneto-optical trapping in a near-suface borehole

“…It is also possible that significant improvements in performance over current state of the art laboratory and portable systems may be possible, through the incorporation of the latest and future techniques [65][66][67][68][69] and technological developments [49,[70][71][72].…”