Quantum batteries toy with time to make energy efficient devices

Quantum batteries promise much faster charging, better efficiency and longer lifetimes than conventional batteries. But for now, they’re thoroughly stuck in the lab.

Chinese and Japanese researchers have nailed down a phenomenon that could – eventually – result in quantum batteries in phones or super-efficient solar panels.

“Current batteries for low-power devices, such as smartphones or sensors, typically use chemicals such as lithium to store charge, whereas a quantum battery uses microscopic particles like arrays of atoms,” says Yuanbo Chen, a graduate student at the University of Tokyo and author on a paper describing the research, published in Physical Review Letters.

“While chemical batteries are governed by classical laws of physics, microscopic particles are quantum in nature, so we have a chance to explore ways of using them that bend or even break our intuitive notions of what takes place at small scales.

“I’m particularly interested in the way quantum particles can work to violate one of our most fundamental experiences, that of time.”

Quantum battery diagram
While it’s still quite a bit bigger than the AA battery you might find around the home, the experimental apparatus acting as a quantum battery demonstrated charging characteristics that could one day improve upon the battery in your smartphone. Credit: ©2023 Zhu et al.

Chen and colleagues tested lasers, lenses and mirrors to charge a quantum battery. They tapped into a quantum effect called “indefinite causal order”, or ICO.

ICO revolves around the idea that causality can flow both ways in the quantum realm. At a classical scale, an event cannot cause something that came before it. But at the quantum scale, it is possible for two events to cause each other: this is a by-product of quantum superposition.

Quantum battery diagram
Common intuition suggests that a more powerful charger results in a battery with a stronger charge. However, the discovery stemming from ICO introduces a remarkable reversal in this relationship; now, it becomes possible to charge a more energetic battery with significantly less power. Credit: ©2023 Chen et al.

“With ICO, we demonstrated that the way you charge a battery made up of quantum particles could drastically impact its performance,” says Chen.

“We saw huge gains in both the energy stored in the system and the thermal efficiency.

“And somewhat counterintuitively, we discovered the surprising effect of an interaction that’s the inverse of what you might expect: A lower-power charger could provide higher energies with greater efficiency than a comparably higher-power charger using the same apparatus.”

The researchers believe that ICO could be used in quantum batteries for low-powered devices, but it could also be applied elsewhere. For instance, the way it interacts with heat means that ICO could be used to make solar panels more efficient.

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