Quantum gravity visualised as a fractal pattern

‘If we had a quantum computer, it could undermine the security of the internet’: Sir Peter Knight, Imperial College

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Chair of the NPL Quantum Metrology Institute and senior research investigator at Imperial College, Sir Peter Knight discusses the journey quantum is making from the laboratory into engineering. “We’re talking about making things that are relevant,” he says, such as fewer roadworks.

“We live in a quantum world,” says quantum physicist Sir Peter Knight. “We don’t often exploit it, but there are examples where we do. The semiconductor is a quantum thing, without which we wouldn’t have classical computing chips.” He adds that the first quantum revolution, which started almost a century ago, “has transformed our world”. Today we are seeing the second, which “hinges on a really weird property of quantum physics in which you can put quantum systems into more than one state at the same time”. 

Knight, who is chair of the Quantum Metrology Institute at NPL and senior research investigator at Imperial College, admits that this is “really freaky stuff” that sounds more like philosophy than science, “but we use it all the time. If you use a satnav you are using this peculiar idea of quantum superposition. That’s how atomic clocks work and they are the basis of GPS. But quantum is going to be so transformative we haven’t even started to think about what it can do. Quantum computing especially is going to knock the socks off everything.”

Compact atomic clocks in satellites are nothing new and because it’s “all done with one atom, it’s fairly straightforward. But how about doing it with more than one atom? Now that’s where the challenges have been. That’s what the research committees have started to play around with. It’s a nice little science challenge, but it’s extremely hard because these quantum systems in superpositions are quite sensitive to the outside world. The more atoms you get involved in this process the more sensitive they are, and it’s incredibly hard to shield them from the outside world.”

If shielding these atoms is the scientific struggle, the advantage in doing so is that “if the systems are extremely sensitive, you can turn it on its head and sense the outside world. The journey for these quantum bits, or ‘qubits’, is to to put them to use in things that are relevant. Obviously, we’re going to proceed with clocks, but a really important practical civil engineering application is to sort out the mess we make when we dig up the road. Half the holes we dig in London are in the wrong place because we don’t know where the buried infrastructure is. If we can increase the precision by a factor of two we could save a fortune and soothe a lot of angry commuters.

“In a country like the UK we have a lot of brownfield sites that need to be developed – how do you know what’s there? That’s why we have surveying companies deeply involved in this technology. They want to know what’s in the underworld, and because of the advantages that come with quantum sensing we can improve things with gravity sensors. The amazing thing about gravity is that you can’t shield it. So, you can always detect what’s underneath. The way we do it is with cold atoms in superposition with lasers. That same set of cold atoms, as we scale it up, will become the beginnings of a quantum memory for computing.”

Speaking of the UK’s National Quantum Technologies Programme (NQTP),  Knight says: “We’re trying to build a pathway towards a distant goal – which is quite challenging, but will have economic benefit.” He describes the NQTP as “the mechanism by which we pull together stakeholder engagement in quantum technology”. The partners are the research councils that fund university projects, Innovate UK, the MoD, through the Defence Science and Technology Laboratory (DSTL), the National Physical Laboratory (NPL), “because of measurement standards and so on”, as well as GCHQ, “primarily through their National Cyber Security Centre”. Knight describes his own role on the board as being “the quantum physicist”.

‘The UK started in quantum earlier than others. But the race is on.’

Sir Peter Knight

“Quite a long time ago, we identified that quantum science in the UK was really strong in terms of a terrific research ecosystem. But we’d also noticed that it was beginning to offer new possibilities in terms of engineering capabilities. Five years ago was the right time to ask how to build on this great science base to pull stuff out of the labs and make a difference to people’s lives. We brought together all the stakeholders we could identify at the Royal Society’s country house, Chicheley Hall, to try to identify what were the opportunities. We asked who needed this stuff and for what? What was the timescale for delivering these things?”

Knight says that the discussion focused on four key areas that remain the focus today and for the future: sensing, imaging, communications and computing. “These all interact with one another and there were people within the NQTP that were engaged in all four of these areas.” From four hubs connected to the universities of Birmingham, Glasgow, Oxford and York radiate spokes in the form of “about 30 universities, as well as a lot of companies”.

Bizarrely, says Knight, the NQTP programme came about as a result of the 2010 trillion-dollar stock market crash (the so-called ‘Flash Crash’), which had been caused by automatic trading algorithms “competing with each other and causing instability”. Knight says that the proposed solution was to accurately time-stamp transactions to see who did what, in what order, to assign credit and blame. “We could see that quantum would deliver chip-scale clocks that could go into the networks to do that time-stamping. That was the seed. Without that we probably wouldn’t have got the Treasury’s interest.” It was an interest that was to trigger a £270m investment in the NQTP to accelerate the translation of quantum technologies into the marketplace to provide stimulus for British business.

Developing his theme of real-world applications for quantum technology, Knight says: “These little quantum systems that spin around, like atomic clocks, are actually quite sensitive to magnetic fields. So, wouldn’t it be great if we could replace those enormous magnetic resonance imaging (MRI) scanners that we currently have in hospitals with something the size of a cycle helmet? On that helmet there will be little cells with lots of laser-excited and monitored atoms processing around, picking up the brain activity. Quantum could be transformative in brain imaging.”

Knight also describes how optical imaging can be harnessed for driver assistance. “One of the things you can do is build quantum states of light that allow you to create detectors capable of picking up single photons. When you do that, it gives you incredible sensitivity. Let’s say you’re driving along in the snow. Where’s the kerb? Never mind about where the next car is. We can use what’s sometimes called short-wave infrared to get through that atmospheric muck to provide insights into what’s going on around you.”

Exactly the same wavelength regions can be used in military applications such as landing helicopters in the desert. “The first thing that happens when you try to do this is a lot of sand gets thrown around and you can’t see the ground. The same technology that tells you where the kerb is can also get you through a sandstorm. Instruments that look for buried infrastructure can also be used to tell you if there is a bomb in that culvert.” Knight says that development work at the Glasgow hub is leading to “cameras that can see around corners”, which will find applications in hazardous industrial areas such as nuclear power plants.

Quantum communication, key distribution, or “rather crudely, quantum cryptography, is fairly well developed in the UK”, Knight says, but it’s important for us to understand how we can safely establish in a communication protocol “who’s who and that we trust each other when we send messages. Quantum key distribution is a method by which you can use the physics of light being sent to and fro to detect and avoid the presence of an eavesdropper. That’s the business of the Quantum Communication hub. They’re already doing key-exchange across fibres in the UK on test systems to check whether messages can be sent at high data rates. That works quite nicely and so part of our current programme is to see if you can extend this to satellite communication, which would be an advantage in long-haul communication.”

Sir Peter Knight

Image credit: Nick Smith

The final current application area of quantum information processing, quantum computing, “is much more of a challenge” in that quantum technology presents a threat to itself. Quantum computers will be able to breach classical computing security due to the fact that “most of the security we have on the internet is based on public key cryptography, of which RSA is an example”. To break an RSA key using classical computing could take millions of years, according to Knight. But with a quantum computer running at the same clock speed, the task would be performed in polynomial rather than exponential time, meaning that the key could be broken in minutes. The uncomfortable outcome is, “if we had a quantum computer it could undermine the security of the internet”.

Knight then explains that Michele Mosca at the Institute for Quantum Computing at the University of Waterloo “has come up with a really interesting equation. First, he looked into how long it will take to build a quantum computer. That’s your threat time. At the same time, he looked at how long it would take to roll out a replacement for public-key cryptography.” His conclusion was that it would take the same time to produce a verifiable quantum-safe encryption technology as it would to build a quantum computer. “So, you start now. Mosca has done more than anybody to explain to the cryptography community that this is urgent.”

At the same time there is a process being led by the National Institute of Standards and Technology (NIST) in the US that is working on the rollout of candidates for a secure replacement for RSA. “That’s one of the big engines and the NQTP is supporting that as well,” says Knight.

But the message is clear: quantum technology could bring down internet security, while the same technology could also supply quantum key distribution, which, if operated correctly, could provide a counter measure of security in response to that threat.

At this point Knight voices the rhetorical question: “Why should the UK taxpayer think that investing in research into quantum technology is a good use of their money?” The short answer is that “it helps us to see the invisible and it protects our information”. What was it, he asks, that persuaded the management at Bell Labs all those years ago “to look into these weird solid-state things called semiconductors? They only needed one application to justify to the board that this was a good investment. It was the hearing aid. And that was because you needed a compact amplifier and you couldn’t do that with thermionic valves. They had no idea of how the transistor was going to transform our world, but they thought the hearing aid was enough to get started. A lot of what we see next will be on the ‘quantum hearing aid’ level. But it’s going to be the ones we can’t see that will truly transform.”

When pushed, Knight says that knowing your internet presence is secure is the game-​changer, while the ability to do quantum imaging “will transform the world”. But the big one is quantum computing: “Everyone thinks it’s all about cracking cyphers, but the real issue will be in simulation. There is a lot of research where we simply run out of steam because we are limited by our ability to compute.” To illustrate this he mentions polymer misfolding, the basis for dementia. “That in itself is not a quantum problem. But if you try to model it with a classical machine, it’s really tough. If you can build a quantum machine you might have a better handle on it. That’s why a lot of people have suddenly become interested.”

Another reason for the uptake in interest in quantum is simply the potential for contributing to the growth of UK plc. “We’re going to see the emergence of practical devices at a price that makes it worthwhile. We started earlier than others. But the race is on. The US has a programme that clearly mirrors ours and China has a rapidly growing programme too. The big strength we have in the UK is that we have everything around a common board. We have scientific excellence. We’ve got strong technologically competent companies that are really engaged. There are industry members on the board of the NQTP. And I think we are doing a lot of things here that the rest of the world is watching quite carefully.”

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