The importance of metrology in the UK’s plans for quantum is critical, as Neil Tyler discovers.

Quantum computing, which is based on quantum physics, is set to have the same impact on the way that we live as the technology behind today’s devices, from computers to smartphones, has had.

Last year, the UK Government announced plans that would see the UK “go big on quantum computing” and unveiled plans to build a general-purpose quantum computer, with the aim of securing 50% of the global quantum computing market by 2040.

Whether that’s possible, quantum computing does provide a powerful way in which to process information that takes full advantage of the laws of physics and in a way that ‘classical’ computing is unable to do.

“By using the principles of quantum physics to process information, you can do a much broader range and type of calculation that you cannot do with normal computers,” explains Rhys Lewis, the Head of the NPL Quantum Metrology Institute.

Quantum physics describes the properties of atoms, electrons and photons which can behave either like waves or particles, resulting in several extraordinary properties out of which it’s possible to create new classes of advanced environmental sensors and systems.

With classical computers information is encoded in bits that are transmitted as an electrical pulse. By contrast, with quantum computers, information is contained in a quantum bit, or qubit, that are particles such as electrons or photons that can be in several states at the same time, a property of quantum physics known as superposition.

What that means is that qubits can encode various combinations of 1s and 0s at the same time and so can process vast numbers of different outcomes.

To really enhance the power of these qubits a process described as “entanglement”, in which pairs of qubits are combined, is required and by doubling the number of qubits available, computing power can be increased exponentially.

“This process creates a very powerful computer,” explains Lewis, “and we’re able to crunch through numbers at unprecedented speeds.

“Quantum computing will allow us to do address a particular class of problem such as modelling new materials or new molecules, for example, which will act as catalysts for original and innovative chemical processes or new pharmaceutical drugs. Theoretically it will be possible to design new chemicals, drugs and alloys, making it possible to accurately predict what a complex molecule might do. We’ll be able to tailor chemicals to particular tasks,” according to Lewis.

All of this is very difficult to achieve with classical computers, but quantum computers are more powerful and can simply find solutions more efficiently.

“They can address problems and create models that are beyond the capabilities of classical computers. Personal delivery services, for example, have become big business and now play a critical role in the economy. By using quantum computers, it will be possible to model routes and optimise delivery schedules. For the likes of Amazon that’s a pressing operational and financial problem.

“Another sector that will benefit from this technology will be financial services. Quantum can be used to manage investments, and portfolios, to optimise returns using new modelling and simulation techniques made possible by this new form of computing,” Lewis suggests.

However, Lewis goes on to make the important point that quantum computing will be dependent on the creation of compatible algorithms and, for many, that it is where the real value will come from.

“It’ll be critical to have the right quantum algorithms (the set of instructions followed by the computer) for the calculation you want to do,” he explains.

Last year IBM unveiled the world’s most powerful quantum processor – the Eagle quantum processor that strings together 127 qubits compared with the 66 achieved recently by the University of Science and Technology of China. It also teamed up with Daimler, the German carmaker, to use quantum computing to model new lithium batteries.

Currently under development IBM’s Condor processor will be able to deliver 1,000 qubits, which will deliver what the company calls

calls the ‘quantum advantage’ whereby it will be able to consistently solves problems faster than a classical computer.

Measurement

Lewis is responsible for NPL’s strategic direction in quantum and for leading NPL’s programme as a partner in the UK National Quantum Technologies Programme.

“Part of the NPL Quantum Programme involves establishing test and evaluation capabilities for quantum timing, communications, sensors, materials and quantum computing and we work closely with a number of Quantum Technology hubs, and with a growing list of industry partners,” he explains.

A key part of NPL’s work is to ensure that there is a metrology framework in place to support innovation and to develop testing and measurement techniques.

“We provide the expertise and facilities needed to underpin the development of quantum technologies in the UK,” adds Lewis, and deliver, “independent test and evaluation, standards and measurement to support new quantum technologies.”

“Measurement is critical, but is also challenging, when it comes to quantum because by its very nature the range of answers can be immense. We need to build confidence in how we measure quantum and that’s critical for the wider industry.”

The UK is aiming to be an international leader in the industrialisation of quantum technology and increase the speed of return on investment for businesses and Government.

NPL can support a wide range of measurements, whether in terms of small current and quantum noise measurements; nanoscale imaging of physical properties for applications in quantum devices; semiconductor optoelectronic devices characterisation and analysis; or cryogenic-temperature semiconductor device characterisation and the physical characterisation of quantum materials and devices to be used in operational environments.

“Companies have access to our capabilities and we’re developing new measurement methods and standards by partnering with the Industrial Strategy Challenge Fund (ISCF) Programme from Innovate UK as well as carrying out research alongside universities in academic-led Quantum Technology for Fundamental Physics (QTFP) projects through the Science and Technologies Facilities Council (STFC),” explains Lewis.

The NPL Quantum Programme was established to ensure that the UK benefits from the national quantum programme and the applications derived from quantum research.

“We’re here to help companies bring new products to market quickly and successfully,” explains Lewis.

Electronic components

Quantum computing, for example, is dependent on very low temperature electronic components based on cryogenic platforms (temperatures less than 1 kelvin) and there are many problems to overcome when it comes to creating and controlling a quantum system. 

“Quantum computing requires a cold operating environment since particles must be in a stationary phase to be measured,” explains Lewis, but that brings technical difficulties.

One is that of bridging the gap between a deep cryogenic quantum system and its control circuitry which operates at room temperature.

Here the reliability of the bridging interconnects is critical but the environment in which they operate is challenging.

Cables must bridge large thermal gradients and can therefore only be made from a limited range of materials.

CryoCoax, a specialist division of Intelliconnect, developed a high-density RF connector for use in cryogenic systems and used 'ganged' rather than individual connectors. The tiny size of each connection with a shared mechanical anchor reduced the footprint of the assembly and simplified the installation of large numbers of lines between stages.

Intelliconnect asked NPL to validate the reliable performance of their connector, which involved numerous tests at low temperature.

There are stringent requirements for ganged solutions to show they are an acceptable substitute for more conventional solutions and the ganged connector must maintain its RF performance under cryogenic conditions and repeated thermal cycling. Working within NPL’s Measurement for Quantum programme, NPL was able to perform tests on the company’s prototype high density connector using a top-loading dry dilution fridge.

After a round of cryogenic testing, the performance of the connector was compared with existing SMA connectors and was found to be suitable for use in compact cryogenic environments with high bandwidth requirements.

It’s that kind of project that is critical in building the testing capabilities that will give companies confidence in their technology but also amongst users and critically among investors in this space.