Dr Vera Guarrera is an experimental physicist in the Atomic Quantum Systems group and an expert on the manipulation of cold and room temperature atomic gases. She develops atomic magnetometers with an interest towards metrological applications and fundamental physics measurements.

Can you explain how your magnetometers work?

We start with a gas of neutral atoms kept
at room temperature or slightly heated. We manipulate the states of the atoms using laser light to create some polarisation in the gas. You can picture the atoms as little magnetic needles, all oriented by the laser beam along the same direction. If a magnetic field is present that is orthogonal to the alignment
of the atomic spins, they start to precess around the magnetic field at a frequency which depends on the strength of the magnetic field.

What can you do with your magnetometers?

Atomic magnetometers are very powerful sensors and complex physical systems. They allow us to precisely measure weak fields generated by our body and the rotation of the Earth, for example. Moreover, they allow us to explore the symmetries of nature and study quantum mechanics in macroscopic systems at room temperature. We can add multiple gases into our cell together, such as noble gases that are less sensitive to the magneticfield, together with the alkali metal used for magnetometry. That way, we can separate the magnetic effects from others, and with almost the same setup, we can create a very powerful gyroscope using basically the same technique.

How can you use these magnetometers to detect dark matter?

Different gases can have different spin proper- ties due to their different nuclear and electron- ic structure. There are theories which suggest that these spins or magnetic moments can interact with some candidates for dark matter. If we build up a clever enough measurement strategy, we can isolate any effects caused by dark matter. We add some more complexity through one or two additional gases, and we can have a very powerful sensor for probing new fundamental physics.

How does quantum behaviour show up in your systems?

The internal states of the atoms are quan- tised, and we can induce genuine quantum effects such as spin squeezing using lasers. However, room temperature atoms move very classically. Recently, we discovered that the atoms arrange themselves in specific patterns or external modes when using some combina- tions of buffer gases. These modes only form in a discrete set of states according to the atoms’ energy. Remarkably, this mimics some of the behaviour of quantum systems, such as quantum oscillators, but in a very classical system.

How can these sensors be used in everyday life?

Our optically pumped atomic magnetometers are already used at the Centre for Human Brain Health, where colleagues from our Atomic Quantum Systems group apply these sensors to measure the magnetic field generated by the brain. Atomic spin gyroscopes are instead used at the National Physical Laboratory to contribute to devices that provide a way of monitoring the position of a vehicle, for example, a submarine, which is navigating for weeks or months in a row without a reliable connection to GPS.