Big Interview

Quantum: non-conventional networking

Tim Spiller1.JPG

Professor Tim Spiller of the Quantum Communications Hub speaks to Natalie Bannerman about the role of quantum in communications and innovations enabling it.

This has been the year that quantum techno-logy has come to the forefront of emerging technologies in the communications space. After being long thought of as purely research-based theory, in 2022 we saw the launch of a commercial trial of the world’s first quantum secured metro network, a collaboration between BT, Toshiba and EY.

One key figurehead in the quantum development space is Professor Tim Spiller, founding director of the York Centre for Quantum Technologies and director of the Quantum Communi-cations Hub, as well as professor of quantum information technologies at the University of York.

When I spoke to him, our conversation started with laying the foundation of what quantum is, particularly in the world of telecommunications.

“The motivation behind these national programmes in quantum technology, not just communications but sensing, imaging and computing, is that there are all these technological tasks that we can perform, where it is possible using something that operates in a quantum way and get an advantage,” says Spiller.

Essentially this means that there are some things that can be done better with quantum technologies than with conventional technology. In communi-cations, the biggest application of quantum technology is security.

Spiller explains that conventional secure communications are underpinned by conventional cryptography, which is mathematical cryptography that’s encoded into software. This way messages can be encoded and then decoded, and while they’re in transmission they are secure and if intercepted can’t be deciphered.

“Quantum communications operates in a different way,” says Spiller. “We underpin the security of the communi-cations by doing something at the physical level not just in the software. Using quantum level light signals, which are either sent down optical fibres or through free space, we’re able to establish shared keys that can then be used for encryption, giving us a guarantee from the physical level that the keys are secure.”

Keys in cryptography refer to a piece of information, usually comprised of a string of numbers or letters which, when processed through a cryptographic algorithm, can encode or decode cryptographic data.

This enhanced security is the biggest advantage of communication, which according to Spiller, is combined with conventional security technologies will produce “a hybrid solution that is the best of everything”. Other areas of application of this technology in communications are that it is a source of random numbers, which is required for both encryption and decryption needs, as well as to do numerical modelling.

Through his work with the UK quantum programme that started in 2014, Spiller says the telco community has been involved from the start.

“BT and Toshiba and others have been partners in in our quantum communications efforts since the very beginning,” he says. “During the first five years, we established various bits of trial quantum communications network with one network around Bristol and one around Cambridge.”

This he says paved the way, and those initial trials showed that quantum communications can work, even work down the same fibre as the conventional encryption data that is being sent, but with the quantum keys.

This in turn led to the first commercial quantum secured metro network from BT, Toshiba and EY, a milestone that Spiller says is necessary and appropriate as it has turned “basic research into lab prototypes, into real working technology that has been deployed in a test network, and now it’s been deployed in a real network”.

With so much investment into quantum, the next natural question would be on the commercialisation of this technology, specifically on the supply side. There appear to be two sides to this question.

The first, Spiller says, is: look at the fibre space. Using BT and other service providers as an example, he believes they are the natural fit for those who would start to use quantum, with the likes of Toshiba and others acting as technology providers, to provide the tech that goes into exchanges to facilitate this.

“I think there will be two sets of relevant companies. There will be the service providers, and then there will be the technology providers and the rest of their supply chains,” he explains.

However, taking quantum beyond a relatively small country like the UK requires communications over rather long distances, which is an entirely different infrastructure class.

According to Spiller, fibre has its limitations because you need amplification, which is unsuitable for sending quantum signals, making things like subsea cables unusable.

“You can’t use current undersea cables for any quantum communication, because all undersea cables have optical amplification built into them when they’re laid, and you simply cannot pass quantum signals through amplifiers.”

Instead, he says, if you want to communicate worldwide using quantum, or at least across water to other continents or countries, “then the logical thing is via satellite.”

As a result, an increasing number of telcos are exploring quantum communi-cations from the ground to satellites.

Though not as advanced as fibre networking in its development, due to the lack of commercial trials to date, there have been some interesting global experiments such as the Quantum Experiments at Space Scale (QUESS) research project that saw Chinese scientists launch the Micius satellite to demonstrate quantum key distribution from space.

“We in the UK we be putting up a number of small satellites – CubeSats – over the next couple of years, and on a longer time scale there are plans for larger satellites to go up,” says Spiller.

This is the future of global quantum secure communications, which brings with it a whole other class of service providers and vendor, as “all of the hardware needs to be provided in a rather different way, so there will be a whole set of new companies contributing”.

While at present this remains largely investigative work, there appears to be enthusiasm and a hunger to see satellite quantum get to the point of commercial trials over the next few years.

In order to use subsea networks as a viable alternative to terrestrial fibre and eventually satellite, Spiller says it will require a whole new fibre infrastructure as well as technology we don’t yet have.

“In order to go very significant distances through fibre, we would

need quantum repeaters or at least quantum relays, which are devices that would effectively amplify the quantum signal in a way that don’t doesn’t disrupt it,” he explains.

This again remains largely experimental and theoretical. It seems to be a long way into the future and of course the pros and cons of both as well as the cost of subsea versus satellite would also have to be considered to determine whether the investment is worth it.

The good news is that Spiller expects to see service providers start to use fibre-based quantum within the next decade. Otherwise he has doubts on its adoption. Satellite will have an understandably longer trajectory.

“I would expect you will know, in 10 years’ time, either BT is using rather more quantum comms than it is at the minute or it will have decided other alternatives will have to be good enough,” he explains.

July saw SK Telekom proposed its approach to quantum cryptography to ITU-T, the standards unit of the International Telecommunication Union, a UN body. Global standards for the technology are closer than we think.

“I think it’s fair to say that quantum communications, compared with other quantum technology areas, has taken a bit of a lead in standards because through ETSI there has been a pursuit of various quantum communications standards for at least the last decade.”

The hyperscalers are also making their own entrance into the quantum space, just not so much in comms, with the likes of Google and IBM focusing on quantum computing.

“If they develop quantum computing they will almost certainly want quantum communications to accompany that technology because if you wish to address a quantum computer from a distance, you may well need quantum communications to do that,” he says.

With a number of trials under its belt, over at the Quantum Communications Hub, Spiller says the next steps in fibre networking would be exploring “reconfigurable networks where you can have more choice about where you send quantum signals and doing more sophisticated forms of quantum communication down fibre”.

With a 2024 launch date, the organisation plans to send into orbit a small satellite to do the next level of investigation with communications

from a satellite down to ground with quantum signals.

The start-up community in quantum in the UK is “actually quite vibrant and healthy right now”, acting as a source for further collaboration with the national quantum hubs up and down the country.

Central to these collaboration efforts would be “to secure further innovative funding so we can continue to work with our industry partners. Then, in a few of years’ time, we’re going to need further funding in order to carry on our own,” says Spiller.