Coventry University researcher shows how time crystals could be used to make quantum batteries

Time crystals may sound like something from a science fiction film, but for physicists the phrase has a very specific meaning.

“A time crystal is a phase of matter in which the system periodically repeats itself in time rather than in space,” says Federico Carollo, Associate Professor at the Research Centre for Fluid and Complex Systems of Coventry University.

The types of crystals that people are more familiar with are solid structures such as diamond, table salt or quartz. These all contain a series of patterns that are regularly repeated within the atoms of the crystal structure. Time crystals are different. They show repeated patterns as well, but these repetitions happen consecutively over time. “In a time crystal, the system does not approach a stationary state, but keeps on oscillating forever,” explains Carollo.

Carollo and his colleagues have been studying the thermodynamic properties of time crystals to understand how these systems can be achieved and maintained. Although they’re still mostly studied with theoretical and mathematical models, time crystals can also be produced in laboratory experiments. One of the reasons why researchers are studying time crystals is that they have potential applications as quantum engines, quantum sensors or quantum batteries.

But to understand how this can be achieved, researchers first need to know more about the thermodynamics of time crystals – the way that energy flows in these systems.

That type of information will make it clear whether the practical applications of time crystals are really achievable and efficient.

When time crystals were first proposed by Nobel Laureate Frank Wilczek in 2012, he assumed that these crystals, like other phases of matter, would exist in an equilibrium state. However, physicists have since learned that the only way to achieve time crystals is if they are not in equilibrium. “This is probably one of the first truly non-equilibrium phases that we understand,” says Carollo.

Carollo and colleagues explored the thermodynamics of time crystals’ non-equilibrium state. Initially, they set out to describe how coupled time crystals could be used for a quantum engine, but they quickly realised that their model was more appropriate to describe quantum-battery applications.

The researchers – which included including Paulo J. Paulino, Igor Lesanovsky and Albert Cabot from the University of Tübingen, Gabriele De Chiara from Queen's University Belfast and Mauro Antezza from the Université de Montpellier - worked with a model in which two systems are coupled. They discovered that these coupled systems can work as a quantum battery more efficiently and can store more energy when in the time crystal phase rather than in the stationary one.

That knowledge can help researchers who are working on the development of quantum batteries but there is still a lot of work to be done before this becomes a reality. 

This research was recently featured in an article in New Scientist. “We had already received some nice feedback from the academic community, but this was an opportunity to go beyond that,” says Carollo.

The magazine coverage introduced a whole new audience to the relatively new concept of time crystals.

For Carollo, having the work covered in New Scientist is also a step toward getting more feedback from the broader community. “It’s easy to get lost in the work, but this shows that people care.”

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Credit: Eva Amsen, Science Communicator and Writer: https://evaamsen.com/