Quantum computing explained

Quantum computers can perform in seconds the kinds of complex calculations that could take years on classical computers – and they’re set to revolutionise the financial sector. Dr Lee Braine, Director of Research and Engineering in Barclays’ Chief Technology Office, explains why the bank is one of the few exploring the capabilities of this revolutionary technology. 

What is quantum computing?

Very few topics are as intimidating as quantum computing. When British science fiction writer Arthur C. Clarke said: “Any sufficiently advanced technology is indistinguishable from magic” he could have had quantum computers in mind. 

Quantum computers often feel like they defy day-to-day logic. They rely on complex physical laws that are entirely different from the relatively simple logic of classical computers. Governed by the unpredictable behaviour of subatomic particles like photons and electrons, quantum computing includes some truly mind-bending ideas – for example how matter can exist in two states at once.

Why all the hype?

Scientists are excited because the scale of its processing power could address problems that are too complicated to be solved using today’s most advanced supercomputers.

It is thought that within years, the weird and powerful properties in quantum computing could deliver breakthroughs that transform the world we live in: it could help us pioneer new life-saving medicines by solving complex chemical problems; improve the response times of emergency services by creating more efficient resource allocation systems; and create more stable financial markets by providing investors with better market analysis.

How is Barclays using quantum computing?

We recognise that quantum computing’s potential is huge and could transform many areas of our business. Our priority for now is conducting specific tests to learn how we could introduce it at Barclays.

Our first successful experiment was conducted by our Chief Technology Office in collaboration with IBM and focused on how quantum computing could help optimise the settlement of batches of securities transactions. As the technology continues to scale, we will be able to run larger experiments and explore different types of potential applications.

We are particularly excited at the prospect of using the technology in the future for financial market analysis to make better predictions about how markets will respond to different events. We’re also looking at risk mitigation, and how we can build ‘quantum resistant’ security systems, to ensure the safety of our clients and partners, and for our business.

Our journey started in 2017, and we spent a significant period of time studying quantum computing until we felt we had a strong internal understanding that we could put into practice. And with a technology that is so new, there is much more we will need to learn in the years to come.

How does quantum computing work?

Quantum computing can crack extremely difficult challenges by taking advantage of the quantum physical laws that govern how subatomic particles – such as photons and electrons – behave. These laws allow systems to exist in more than one state at the same time (a phenomenon which we call ‘superposition’) and particles to be tightly correlated (a phenomenon which we call ‘entanglement’).

What’s actually inside a quantum computer?

A quantum computer circuit is made up of ‘qubits’, a new memory unit like ‘bits’ in a classical computer circuit. However, because qubits contain subatomic particles in a state of superposition, they can exist as both 0 and 1 at the same time – unlike ordinary bits which can only exist as either 0 or 1. As a result, a collection of qubits contain exponentially more information than the same number of classical bits.

So, in a quantum computer circuit with many entangled qubits in superposition, we can perform calculations on far more variations of each of data item, almost instantaneously. This is what will allow us to solve some complex problems faster on a quantum machine than a classical machine.

There’s a catch – quantum computers that are useful in practical terms don’t exist yet. Right now, researchers are still focused on developing quantum computing algorithms and building experimental quantum computers. Actually constructing the machines is a delicate and complicated process, as they can only operate in highly specific and hard-to-maintain conditions, such as near absolute zero temperatures.

Experts are split on when we will be able to build larger quantum computers that can deliver on researchers’ theories by solving real-world problems. Some think we could make decisive breakthroughs within five years; others think it could take ten years or more.

Researchers have been able to build quantum computers that demonstrate progress. For example, in 2019, scientists at Google declared that they had built a quantum computer which solved a specific numerical challenge that a classical computer couldn’t complete in a lifetime.

How will quantum computing first be used in modern life?

Medical research is among the most discussed initial applications for quantum computing. Until now, the need to repeatedly conduct a test with many potential outcomes on an unpredictable disease or a new medicine has sapped time and resources. Quantum computers’ supercharged ability to process data could help to discover life-changing medicines that would never have been achievable before.

Quantum computers could also help simplify complex national and global systems. For example, governments could use the technology to re-organise intricate infrastructure like roads or power networks more efficiently and at a lower cost – by finding the optimum balance between values such as cost and efficacy.

How could quantum computing affect the world of work?

Quantum computers could help us solve macro challenges in work – but they aren’t going to start taking over employees’ day-to-day tasks.

We anticipate that they will be used to identify ways to optimise systems that connect businesses or even whole industries together like global supply chains and trade flows – because the hidden inefficiencies in these systems currently waste enormous sums every year.