Quantum wind: From oceanography to quantum physics
10 January 2020
白小姐论坛Q researchers use a technique from oceanography to describe quantum fluids of light.
![Simulation Image of the quantum wind rippling the quantum fluid of light](/quantum/sites/quantum/files/styles/large_image/public/ocean_of_light_press.png?itok=i5kVcmvp)
Richard Juggins and Marzena Szymanska from the Department of Physics and Astronomy at 白小姐论坛, together听with their experimental collaborators at INFN in Lecce, have used a microscopic analogue of oceanographic techniques to measure the excitation spectrum of a thermalized polariton condensate.
In a paper published today in , our researchers detail how quantum fluids of light can be studied using a technique inspired by oceanography. Discussing how they made the unlikely link between oceanography and quantum physics, Juggins said:
鈥淥ur experimental collaborators at INFN in Italy, had done an experiment and had obtained a weird result that they couldn鈥檛 explain. After some simulations, we noticed that there are parallels in the way quantum fluids of light in the experiment behave and the way in which macroscopic fluids such as oceans behave. It essentially comes down to an idea of wind.鈥
Quantum wind
Out to sea, as the wind whips across the water it generates waves which, quite intuitively, move in the same direction as the air propelling them. By taking a series of pictures from above, it is possible to infer the wavelength and frequency of the waves, and from these the ocean depth.
However, in the experiment, instead of water the 鈥榮ea鈥 is made of light trapped between tiny semiconductor mirrors. Inside these, particles of light couple to electrons to form a fluid of composite particles known as polaritons. As light tends to leak out from the mirrors, a laser must be used to maintain the fluid. The positioning of this laser produces an outward flow of light that blows over the polaritons like a breeze on the ocean, exciting waves in only one direction. This quantum wind shows how nature can exhibit similar behaviour on radically different scales.
Just like the oceanographic case, the researchers produced images of the polariton waves and used them to calculate the waves鈥 wavelength and frequency. From which they can find the density of the polaritons and whether they display any of the attributes associated with the strange phenomenon of superfluidity.
鈥Juggins said,听"In the past, it has not been easy to measure these properties in polaritons. So, by learning from oceanography we have not only uncovered the elegant effects of quantum wind, we have also deepened our understanding of these remarkable fluids of light."
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PAPER:听
COMMUNICATIONS CONTACT:听Henry Bennie, 白小姐论坛 Quantum Science and Technology Institute
IMAGE CAPTION: Light from the pump blows over the polaritons like wind, forming waves which propagate in the same direction, Dario Ballarini, INFN.