Quantum supremacy: What can we do with a quantum computer?

It could be decades before we have quantum computers that can do anything useful, but once we get there, what will we use them for?

The first use could be in chemistry. As the physicist Richard Feynman once said, “Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical.”

Quantum computers could help with drug development

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The forces, molecules, particles and more involved in a chemical reaction all interact in different ways. When trying to simulate what will happen, the combinations can quickly get out of hand, at least on a classical computer. Quantum computers are particularly good at dealing with huge numbers of possibilities.

According to researchers at Microsoft, simulating a single water molecule requires 16,000 bits on a classical computer. But a quantum computer would need just 24. The hope is that this means a quantum computer could reveal some of chemistry’s most elusive secrets, such as how to improve the Haber-Bosch process.

This is used to help make fertilisers for crops around the world, but it is energy-intensive – it is responsible for about 1 per cent of annual global CO2 emissions. So chemists are on the hunt for a more-efficient replacement. The Microsoft team estimated that just 100 qubits, double the number in Google’s quantum computer, could be enough to crack this nut open.

There is also hope that quantum computers could improve our understanding of high-temperature superconductivity. Superconductivity occurs when electrical charge moves through a material without resistance – something that could vastly improve the efficiency of power grids, which lose a lot of energy to heat as electricity is transferred across networks. Currently, we can only make materials superconductive when they are extremely cold, which requires lots of energy, nullifying some of the gains in efficiency.

By looking at the huge number of possible ways that atoms in a material interact, quantum computers may unlock a way of making superconductors at much higher temperatures. That is, if it is possible at all.

The pharmaceutical industry could also benefit from quantum computing. Drug design relies on predicting how a protein folds based on its building blocks and the external forces acting on it. Quantum computers could considerably shorten the time required to work out how different proteins will act, although quantum algorithms designed for this purpose will need to be created – something teams around the world are working on.

However, all of this is probably just scratching the surface. Classical computers were first used for performing calculations or solving technical tasks, like attempting to crack secret codes. At the time, it would have been hard to imagine that, less than a century later, billions of people would carry hand-sized computers around with them everywhere they went. Imagining what they would use them for would have been even harder.

The same is true for quantum computers. The first quantum computers will be extremely expensive and used for niche applications. But with so many possibilities after that, predicting what will happen is nearly impossible. Perhaps one for the quantum computers?

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