You are late for an important meeting. Just as you are leaving the house, you realize that your phone is flat.
Imagine being able to charge it almost instantly by exploiting the strange rules of quantum physics. This is the promise of quantum batteries.
My colleagues and I at CSIRO have developed the world’s first quantum battery prototypes – and the direction technology has taken is astounding.
Collective quantum effects
You may have heard of the special quantum effects of overlap and entanglement, which allow mostly very small objects to behave very strangely. They may also allow quantum computers to solve problems that conventional computers cannot.
A strange feature of the quantum world is what are called “collective effects”. They are what give quantum batteries their unique properties.
Under the right circumstances, quantum battery storage units do not act individually, but behave collectively. In a counterintuitive twist, this means the units charge faster together than if they were charged alone.
Let’s say your quantum battery has N storage units and each unit takes one second to charge. The collective effects mean that if all units are loaded at once, each unit will only take 1∕√N seconds to load.
This means that the bigger your quantum battery, the less time it takes to charge. If doubled in size, charging will take a little more than half.
It’s as if each unit somehow knows there are other units around and their presence makes the unit charge faster. Strange, isn’t it?
This is radically different to how conventional batteries work, where larger batteries typically take longer to charge. That’s why it might take an hour to charge your cell phone, but your electric car needs all night.
Building a quantum battery
The idea of a quantum battery was only a theoretical curiosity for a long time. But in 2018, I set out to demonstrate that they could be built.
In 2022, working with colleagues in the UK and Italy, we built a quantum battery prototype using an organic microcavity – a kind of small, complex multi-layered sandwich made of several different materials that captures light in a special way.
And we were able to show for the first time the exotic behavior where larger quantum batteries actually take less time to charge.
In fact, we were able to demonstrate that the charging time decreases as 1∕√N, where N was the number of molecules in our battery. The more molecules we include, the faster the battery charges – just as theory predicted.
One thing this first prototype didn’t have was a way to extract power from it. To do this, in our latest studypublished in the journal Light: Science & Applications, we added additional layers to our device that converted the energy into an electrical current.
This marks a major step towards a practical quantum battery.
Progress still to be made
So why aren’t we seeing quantum batteries in stores?
Well, the capacity of quantum batteries is still small (a few billion electron-volts), and the time they hold their charge is very short (a few nanoseconds). This means that quantum batteries are too small to power conventional devices such as your mobile phone, at least for now.
But quantum batteries could be perfect for powering quantum devices such as quantum computers. In fact, quantum batteries can be correct solution Quantum computers must work on a larger scale and become practical.
While we don’t yet have practical quantum batteries, we are working on ways to increase the size of our prototype and extend its charge-holding time. We hope to create a hybrid design that combines the extraordinary charging speed of the quantum battery with the long storage time of the classical battery.
The progress we have made is a testament to the century of theoretical work done by quantum scientists before us.
Charging the battery of our first prototype took nanoseconds. The Wright brothers’ first airplane flight took a little longer. Progress takes time – but quantum batteries are certainly on our horizon.
James Quach is the scientific leader, Quantum Battery Team, CSIRO
This article was reprinted from Conversation under a Creative Commons license. Read on original article.
