There are many good articles and reports that explain how a quantum computer works, not least the technical roadmap on the NQIT website. But even without a detailed explanation, readers of ITNOW will understand that if a quantum bit (qubit) can compute in the superposition state of being both ‘on’ and ‘off’ at the same time, a quantum computer has the extraordinary capability to run algorithms in ‘parallel’ on a superposition of a great many paths. As Wim van Dam of the University of California puts it, ‘to describe the state of 100 quantum bits you might need 140 terabytes of classical memory’.
That is impressive and 100 qubits appears not to be a very large number - Google’s Bristlecone quantum computer has 72 qubits already. The much-publicised qubits built by Google, IBM, Rigetti and others are impressive achievements but unfortunately they are not yet reliable and cannot match the predictable behaviours of the classic bits of today’s digital computers.
A Universal Fault-Tolerant Quantum Computer (UFTQC) will be an extremely powerful device with even a modest number of qubits and capable of computations that are beyond the classic computer’s capability, but building just one such fault-tolerant qubit is still a formidable challenge.
Rising to the challenges ahead
The qubits that can be built today have errors that limit practical computation. These errors can be overcome by combining multiple physical qubits to correct each other’s error and so together create a fault-tolerant or logical qubit. The number of physical qubits required to build a fault-tolerant qubit is a function of the size of the error and for most of the current qubits, that number is still beyond what we can build.
That means the challenge is not only to build quantum computers with more qubits, but more importantly, to improve the precision of the physical qubit. For that reason, and until we can build fault-tolerant qubits, the term quantum volume which includes the number of qubits and their precision including the fidelity of the connection between them, is a more apt measure of capacity than the mere count of qubits.
Scientists and technologists are making good progress on all fronts and the leading qubit technologies are on a steady path to reduce error rates and they are also learning how to scale machines, i.e. build more qubits and connect them together, the latter being another technical challenge. Although few will commit to a timeline, the developments provide ample confidence that fault-tolerant quantum computers are technically possible and will become an important part of the IT landscape.
Seeing beyond today’s limitations
More near-term, is the prospect of quantum computers that are not error-corrected but ‘noisy’ they nonetheless may be just reliable and big enough to perform tasks that are beyond the capabilities of classic computers.
These machines referred to as Noisy Intermediate-Scale Quantum computers (NISQ’s) are expected to become available in the next few years. That prospect means that there is not only a competition to build qubits, systems and software environments but also a competition to discover the first NISQ applications that create value.
The capabilities of NISQ’s may be limited, but if a quantum advantage can be established, it can be expected that the rewards from the first applications may prove to be phenomenal, as was the case for classic computing.
To illustrate the point, it is not just the big technology companies that are investing in the development of quantum computers: commercial corporations now also invest time and resources to understand the applications of quantum computing. Rigetti’s $1million Quantum Advantage Prize and Airbus’ Quantum Computing Challenge offer further enticements.
UK Quantum Technologies Programme
Well before we arrived at the possibility of a quantum computing advantage in the next few years, the research community in the UK was an established leader in quantum technologies. For example, the University of Oxford, the lead university of the NQIT Hub, has 38 separate research teams, with a total of around 200 researchers, which makes it one of the world's largest centres for quantum science. Similar centres of world-leading expertise can be found in other UK universities.
The UK also has a thriving technology industry. As an illustration, the UK photonics industry, an important enabling sector for quantum technologies, already contributes £13bn to the UK economy and employs 65,000 people.
Based on these and other strengths, the potential for quantum technologies to benefit the British economy was recognised early and in 2013 the UK government announced an investment of £270m over five years into a National Quantum Technologies Programme.
Delivered by the Engineering and Physics Science Research Council and Innovate UK, the programme aims to accelerate the translation of quantum technologies into the marketplace, with a focus on quantum sensors, quantum imaging, quantum secured communications and quantum computing & simulation.
A new age of UK led development
This programme has supported investments in research, innovation, skills and technology demonstration and working with industry in collaborative R&D and industry-led projects, to help understand more about the market and use for quantum technologies, develop components or bring products to market.
Centres for Doctoral Training in quantum technology have ensured the next generation of researchers in this field is supported and a Quantum Metrology Institute at the National Physical Laboratory (NPL) is also part of this programme.
These and other activities have helped to grow the total government investment to more than £350 million since 2014 with growing innovation spending by UK-based companies too.
Now, in the final year of the first five year national programme, there is unanimous agreement that the programme has delivered. The technologies in all four focus areas deliver results that are among the best in the world and rising readiness levels and scalability is being demonstrated. Established UK technology companies are investing and some are already reaping the rewards of being leaders in key enabling technologies such as specialist lasers or dilution fridges.
New ventures are receiving investment with an aim to develop technologies or applications including in the new emerging field of quantum computing tools and applications. International companies have started to make investments in the UK and several of the big technology companies have established partnerships with UK universities, or in one case the Science and Technology Facilities Council. Quietly, the UK is making itself the go-to nation for quantum technology and commerce.
The go-to nation for Quantum Computing
There are, of course, many other nations and organisations developing quantum technologies. The UK programme was, however, the first to recognise the need to coordinate research, industrial and public engagement. The scientific results, technological progress and broad scientific and industrial participation provide the confidence that the UK can compete with all other programmes and companies.
The results of the programme were also considered in detail in 2018 by the House of Commons Science & Technology Committee’s Quantum Technologies enquiry. The Committee’s recommendations have been largely accepted by the UK Government, which has committed itself to a continuation of the UK Quantum Technologies Programme, with a further five year programme and a total investment exceeding £400m over six years. This includes refreshed technology hubs, an expanded skills development programme, £173m grant funding for industry led projects to drive innovation and commercialisation and a new and world’s first: A National Quantum Computing Centre (NQCC).
The National Quantum Computing Centre
Building on the UK science and technology that includes the world’s most precise qubits and uniquely scalable architectures, the NQCC will work towards achieving a fully scalable, fault tolerant, general purpose quantum computer, whilst also working on intermediate systems. It will be a focal point for the emerging UK quantum technology industry: suppliers, system integrators, developers and users in industry, science and the public sector.
The applications of quantum technologies and especially quantum computing are not all known yet. But, there is a common expectation of new scientific discovery and new products and services through the use of quantum technologies. To ensure that the risks and opportunities are well understood and that they will have the broadest positive impact, the UK Quantum Technologies Programme includes a Responsible Research and Innovation (RRI) activity and public outreach activities to make the UK a fully quantum literate nation.
For any individual or organisation who wishes to get involved, the NQIT website provides in-depth reports that can be downloaded and links and contacts for more information and how companies can participate in research and technology development on quantum information technologies. Discover the UK Quantum Technologies Programme with links to all the technology hubs as well as the 2016 Blackett Review with a comprehensive overview of the application of all quantum technologies. Also see the House of Commons Science & Technology Committee Report on Quantum Technologies.