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Cambridge University Science Magazine
From gigantic whirlpools to milk in coffee, the idea of a liquid vortex is familiar to many. Less known is the fact that these structures of circulating fluid can also be seen in ‘quantum fluids’, which are fluids that exhibit quantum mechanical properties (e.g. wave-particle duality or the quantization of energy). However, the task of forming large and stable quantum fluid vortices has previously been met with great difficulty. Now, a study from Samuel Alperin and Professor Natalia Berloff at the University of Cambridge has shown theoretically that such giant structures can stabilise in quantum fluids. The results are useful in understanding quantum dynamics but can also be extrapolated to understanding the nature of black holes, which behave similarly to quantum vortices.

For making the ‘quantum fluid’, the researchers used a quantum hybrid of light and matter, called a polariton. Polariton fluids are constantly expelling light and need fresh light stimulation to survive, making them dynamic and unable to settle. This dynamic property of the quantum fluid was exploited by researchers in their theoretical model for the vortex: by having the light stimulation as a ring around the liquid (rather than directly on the particles), the inward ‘drain’ of light into the system causes the vortex to form. However, the researchers highlight that this work represents just the beginning for understanding giant quantum vortices, as the properties of such structures need to be further investigated.

Written by Adiyant Lamba. Artwork by Josh Langfield.