Optical Atomic Magnetometry

Quantum sensors based on the Larmor spin precession of optically-pumped atoms in room-temperature alkali vapour cells are currently the most sensitive magnetometers available. These optically-pumped magnetometers (OPMs) have been shown to operate with magnetic field sensitivities of below 1 fT per √Hz - even better than conventional superconducting SQUID systems [1].

In collaboration with the Clinical Imaging Sciences Centre (CISC), we are investigating ways in which to use such sensors to perform magnetoencephalography (MEG) - a sophisticated tool that yields rich information on the spatial, spectral and temporal signatures of human brain function. However, since the magnetic fields produced by the brain are so weak (and reduce strongly with increasing distance), current MEG techniques are limited in the signal-to-noise ratio and spatial resolution that can be obtained.

Recent work suggests that OPMs might be a viable alternative to superconducting detectors for MEG measurement [2]. It is possible to bring the sensors to within a few millimetres of the scalp (in contrast to several centimetres), thus promising increased sensitivity compared to traditional SQUID systems. Operation at room-temperature also alleviates the need for any cryogenic cooling, which typically requires liquid helium that is costly and in short supply environmentally.

In addition to the high signal-to-noise offered by OPMs, their flexibility in terms of positioning of the sensors around the head could drastically improve studies of brain activity in infants - subjects who are currently measured using ill-fitting enclosures designed for adults.

Figure credit: [2]

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[1] I. K. Kominis. et al. "A subfemtotesla multichannel atomic magnetometer". Nature 422, 596-599 (2003).

[2] E. Boto. et al. "On the Potential of a New Generation of Magnetometers for MEG: A Beamformer Simulation Study". PLoS ONE 11, (2016).