An experimental but fully functioning quantum battery system may have helped nudge the technology a small step closer to real-world applications. The quantum devices can charge and discharge a little like standard batteries, but the process gets faster as you make the quantum battery larger.
Batteries that work by harnessing quantum effects instead of chemical reactions, known as quantum batteries, have many theoretically exciting properties, such as fast charging and discharging. But no one has managed to build a working quantum battery system – until now.
“No prior work had demonstrated a fully functioning quantum battery that could charge, store energy and discharge electrical power in a single device. Our devices do exactly this,” says at the Commonwealth Scientific and Industrial Research Organisation in Australia.
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His team’s battery is a layered device that contains a microcavity – a tiny empty space – surrounded by mirrors, electrodes and several other materials. This microcavity is filled with molecules made from copper, carbon, hydrogen and nitrogen. To charge the battery, the researchers illuminated it with laser light. This made the molecules more energetic, meaning they stored some of the energy from the light.
Because the microcavity is mirrored, the laser light is trapped there. Consequently, the quantum states of this light and of the molecules become entangled, or inextricably correlated in a way that has no counterpart in traditional batteries. Quach says that this entanglement changes how energy transfers from the light to the molecules in such a way that versions of their battery containing more molecules charge faster than those with fewer.
The battery’s charging time was approximately inversely proportional to the square root of the number of molecules – meaning that if a battery containing 10,000 molecules charged in 1 second, a battery containing a million molecules would charge in just 0.1 seconds. The researchers tested battery sizes ranging from 280 to 790 trillion molecules with charging times as brief as millionths of a billionth of a second. The same trend was true of the battery’s discharging time.
Getting the quantum battery to work when using so many molecules is impressive, says at Trinity College Dublin. “They’re showing a [quantum] effect and that they can use it stably with a large device,” he says. However, it’s still unknown exactly how the new battery could be used in a technologically meaningful way because it isn’t yet clear how much energy it could store and how it would interface with other devices.
In Quach’s view, there are many areas where quantum batteries could be revolutionary because of their fast charging and discharging, such as portable electronics and renewable energy storage, and his team is working towards those applications. The two challenges on their agenda now are increasing the amount of energy that the battery holds and charging it with sunlight instead of laser light, he says.
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