The Quantum Charging Advantage

One of the main things that is holding back the adoption of electric vehicles is the time that they take to charge. Although that time is dropping through advancements in technology, people who are used to filling their tank almost immediately at a gas station do not want to hang around for the half hour that it would take to charge their EV on a supercharger to get sufficient range to reach their destination. That amount of time will fall further in future as new higher voltage architectures are introduced and other technologies become commercially viable, but these advances are taking seconds or minutes off the charging time, rather than bring it down to the equivalent of the gas pump.

One of the main challenges to be overcome is that there is a limit to how quickly a battery can be charged safely. Lithium batteries are the most suitable for EVs at the moment, but if they are charged too quickly, they can overheat and become dangerous. Scientists and researchers around the world are looking for a solutions that will allow faster charging. Could quantum batteries be the solution? Quantum batteries were first proposed in a paper published by Alicki and Fannes ten years ago. The paper theorized that quantum resources, like entanglement, could speed up the battery charging process by charging all cells within the battery simultaneously. Modern large-capacity batteries are constructed from many cells. Collective charging is not possible in these types of batteries, and the cells are charged in parallel independently of one another.

The difference between collective charging and parallel charging can be measured by a ratio called the ‘quantum charging advantage’. Around 2017, it was proposed that there were two sources behind the quantum advantage – the ‘global operation’ where all cells talk to all others at the same time, and an ‘all-to-all coupling’, in which every cell can talk with every other one, but every discussion only has two participants. Recently, scientists from the Center for Theoretical Physics of Complex Systems within the Institute for Basic Science (IBS) looked into these questions in a new paper for Physical Review Letters. The paper found that all-to-all coupling is irrelevant in quantum batteries, and global operations forms the whole of the quantum advantage. The group also found the exact source of the advantage and proposed an explicit way of designing quantum batteries. Finally, the researchers were able to precisely quantify how fast the charging speed could be achieved.

The maximum charging speed increases linearly with the number of cells in ordinary batteries. The study found that quantum batteries can achieve quadratic scaling in charging speed – if a typical electric vehicle has a battery that contains around 200 cells, quantum charging would provide 200 quicker charging than classical batteries. This means that home charging times would be cut from 10 hours to about 3 minutes. At high-speed charging stations, the charge time would be cut from 30 minutes to seconds.

The implications of quantum charging go far beyond electric cars. For example, the technology may find uses in fusion power plants, which require large amounts of energy to be charged and discharged in an instant. However, there is a long way to go before these methods can be implemented in practice, but the new findings may help speed up research in the subject.