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Laser Light Cools Quantum Liquid

Australian researchers have used laser light to cool a special form of quantum liquid called a superfluid. Lasers are widely used to cool gases and solid objects, but they have never before been applied to cool a quantum liquid.

Superfluids are quantum liquids with a strange property: once started, the flow of a superfluid never stops. This unique property is a key feature of many applications proposed for superfluids.

“The applications of this research range from improved sensors for navigational systems to the development of quantum devices and fundamental exploration of the quantum physics of turbulence, or the turbulent motion of quantum fluids when cooled to temperatures close to absolute zero,” said Dr Glen Harris of the ARC Centre of Excellence for Engineered Quantum Systems.

In the experiments, which were published in Nature Physics (http://tinyurl.com/z2j23mr), a superfluid helium film was formed on a silicon chip. A bright laser beam was then used to draw energy out of waves on the surface of the superfluid, cooling them.

In addition to laser cooling, the research team showed that extremely precise measurements of superfluid waves could be obtained by combining a superfluid with microphotonic lasers.

The project’s Chief Investigator, Prof Warwick Bowen, said that this research provides a pathway to replace inertial sensors used in navigation systems. “Previous experiments have shown that ultra-precise inertial sensing is possible using superfluid helium,” he said. “However, these experiments relied upon bulky architectures somewhat akin to a plumbing system for water.

“The ability to cool, measure and control superfluid waves on a silicon chip brings a new level of scalability and integrability to such sensors.”