Measurement with a deployable quantum magnetometer

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Double-resonance optically pumped magnetometers (DR-OPMs) offer a powerful and flexible quantum sensing tool with applications in healthcare, geomagnetics, manufacturing and fundamental physics. The last decade has seen developments in the underpinning science and component microfabrication which result in greatly increased potential for impact in these real-world applications. OPMs now offer Femtotesla magnetic field resolution (part-per-billion sensitivity in Earth's field), a regime in which only cryogenic SQUID magnetometers offer comparable performance. However, compact, portable, cryogen-free OPMs can be used in many applications where the size and cost of SQUID magnetometers is prohibitive. OPMs will be applied to portable magneto-cardiography and magneto-encephalography for medical research and diagnosis, where their scalability and form factor unlock new capabilities for portable sensor arrays. In geomagnetic measurements the intrinsic calibration of OPM magnetometry against alkali atomic energy levels is a significant advantage over widely-used inductive magnetometers, offering calibration-free measurement for surveying, defence and navigation. OPMs can also be configured for resonant narrowband detection of oscillating magnetic fields in the sub-MHz band, benefiting from the system's frequency-invariant limiting quantum noise sources, rather than the classical Johnson-noise-limited inductive sensors widely used for these signals. This tuneable detection mode is a key technology for low-field hyperpolarised NMR in pharmaceutical and chemical manufacture. The sensitivity and accuracy of DR-OPMs also has important applications in networked fundamental physics searches for cosmological axions and domain walls. This project will focus on the development and demonstration of DR-OPM configurations tailored to maximise performance in specific applications. This will entail the development of sensor modes and control firmware in the laboratory, aiming to work at quantum-limited precision in an optimised test environment, leading on to sub-system optimisation and demonstration of field-ready prototypes in real-world applications. The development of techniques and system components in the lab will lead forward to the design and demonstration of field systems in collaboration with our network of end users. This work will build on our expertise in DR-OPM readout and feedback schemes and demonstrated capability in specialised subsystem design, including compact laser-optical systems and micro-fabricated alkali vapour cells. The combination of increasing subsystem performance and readiness with new techniques in DR-OPM operation, such as digital spin maser feedback schemes, places this research at a critical translational stage. Laboratory-based research developments now have potential for field application and rapid impact. Increasing end-user interest is driven by technology demonstration with increasingly high-performance devices. This project will exploit these opportunities, demonstrating and enhancing the impact of quantum sensors in magnetometry, and it will be an integral part of ongoing quantum technology development.