Collaboration with the University of Sussex and SYRTE - Observatoire de Paris

Ultra-cold atoms (at micro-Kelvin temperatures or below) provide some of the purest quantum states available as they are highly separated from the ‘noisy’ classical environments by the ultra-high vacuum they need. Over three decades of development in manipulating these atoms has provided physicists with a huge range of high precision tools, a deeper understanding of fundamental physics, and a number of practical applications beyond the laboratory. This latter aspect has led to a worldwide interest and funding into ‘quantum technology’ in which the stranger aspects of quantum physics (e.g. superposition and entanglement) are used for applications in sensing, communications and computing. This project forms part of the UK Quantum Technology Hub for Sensors and Metrology.

Laser cooled neutral atoms are especially useful as they have internal structure, mass and can be made sensitive (or insensitive) to electric, magnetic and gravitational fields. One important aspect is the ability to trap these particles for long periods of time, which increases their ability to sense forces. A suitable analogy is a laser interferometer which can record minute variation in length via interference between two beams. The longer the arms of the interferometer, the more sensitive the device – as highlighted in the LIGO detector. At very low temperatures, atoms begin to exhibit (de Broglie) wave-like properties in exactly the same way and we can form similar interferometric sensors.

A Sagnac interferometer has a ring geometry which allows the (atomic or light) waves to circuit nearly indefinitely. The sensitivity of the interferometer is proportional to the area enclosed multiplied by the number of cycles around it. Thus one can have huge increases of sensitivity whilst maintaining small overall dimension. This requires very low loss per circuit/cycle. There is, therefore, a large interest in making cold atom Sagnac interferometers with low losses because of the huge potential gain in sensitivity. This can be achieved be ensuring the trapping ring is highly uniform with no ‘input and output’ ports. This has been difficult to achieve as most magnetic traps which use wires require connection to an external current source.

Induced currents, however, do not require such connections and also allow for high power electronics to be situated externally to the ultra-high vacuum – greatly simplifying the experimental design. A trap based on such currents is formed by producing a ring shaped magnetic minima near the inner radius of a millimetre sized metallic ring. At this point there is a cancellation between the external and induced microwave fields which atoms are attracted towards.

Such a trap has yet to be experimentally verified, however there has been significant theoretical research. This experimental PhD, supported by theory from the University of Sussex (joint supervision from Professor Barry Garraway) will develop the first inductive ring trap using microfabrication technology, microwave electronics and laser cooling and trapping of atoms. Support on magnetic traps and atomic gyroscopes will be provided by the Observatoire de Paris.