Discovery! - UK quantum computing technology moves towards commercialisation

Dr Andrew Fearnside, senior associate attorney specialising in quantum technology at patent law firm Mewburn Ellis LLP, outlines the latest investments in quantum computing, explains how it all works and why we should be excited

As part of a wider £1 billion National Quantum Technologies Programme to commercialise UK quantum technologies, the UK government has announced 38 new projects that will receive over £70 million of government investment. The grants will be matched with over £30 million of private investment.

The projects, which involve over 80 companies and dozens of universities across the UK, aim to solve key industrial challenges using advanced quantum technologies and boost the UK's leading position in quantum technologies.

Around a third of the projects receiving funding concern quantum computing, and include developing quantum computer hardware as well as one of the world's first quantum computer operating systems.

‘DISCOVERY' is one of these projects and receives £10m to address technology barriers to commercial quantum computing. This three-year project, now underway, is the largest industry-led quantum computing project in the UK yet seen. The consortium handed this task includes M Squared, Oxford Ionics, ORCA Computing, Kelvin Nanotechnology, TMD Technologies, and the Universities of Glasgow, Strathclyde and Oxford, along with the National Physical Laboratory (NPL).

Coordinated by M Squared, a Glasgow-based photonics and quantum technology company, these nine organisations, each a leader in its field, will develop routes to commercialising quantum computing technologies based on three leading contenders for use in quantum computing: neutral atom qubits, trapped ion qubits and optical qubit approaches.

Quantum Computing

Quantum computing as an idea was virtually unheard of just a decade or so ago. Lately, it has burst into the public's imagination. Initially, the idea was just that - an idea - since, at that time, no one knew how to build a quantum computer. Recently though, that situation has changed. Driven partly by concerns about the slowing of Moore's law, which has driven computing performance for decades, and partly by excitement about the potentially huge computational power of quantum computers, recent progress in creating the basic quantum hardware and algorithms seems likely to make quantum computing a reality.

The most basic element of current ("classical") computers is the "bit" - the elementary component it uses to represent information. In a quantum computer that's known as a quantum bit, or "qubit". Qubits outperform classical computer bits thanks to two uniquely quantum effects: superposition and entanglement.

Unlike classical computer bits, superposition allows a qubit to have a value of not just 0 or 1, but both states at the same time and any number of states in between. This enables potentially a colossal amount of simultaneous computation. Entanglement enables one qubit to instantaneously share its information with other qubits within the quantum processor core, enhancing the superposition effect. The effect of these quantum interactions is to double the processing capability of the quantum processor core with every additional qubit. For example, a core using five qubits can effectively do 32 computations at once, but a classical computer would have to do those 32 computations one after the other.
How hard can it be?

Prototype quantum computers exist today, but the holy grail for quantum technologists is creating a commercially scalable quantum computer that can compute indefinitely without errors.

One of the big differences between classical and quantum computers is how they handle noise in their bits/qubits. A classical bit is either just one or zero, so even if a bit value is slightly off (noise) it's easy to remove that noise: "close enough" is good enough. However, because a qubit can be any value between one and zero, qubits can't easily correct small errors (noise): what looks like a small error could be a legitimate qubit value and vice versa. As a result, small signal errors creating by a quantum core, or stray signals getting into the core, can lead to corrupted computation.

Clearly, qubits are very powerful but very fragile. The ability to make use of them requires that all of the qubits are fully entangled, or quantum-interconnected, very precisely controlled and well isolated from the outside environment. External disturbances like light or heat can quickly destroy them, and so careful engineering is needed to manage this. Fundamentally, it's an engineering problem.

At present, there are several promising approaches to commercially viable quantum computing. Technology giants such as Intel, Microsoft, IBM, and Google are pumping tens of millions of dollars into quantum computing research with no agreement on which qubit technology will work. No one yet knows what type of qubit will power a practical quantum computer. The DISCOVERY program will focus on three methods that offer the highest performance demonstrated to date: neutral atom qubits, ion qubits and optical qubits. Although these approaches represent the state-of-the-art in demonstrated hardware, barriers to commercial deployment remain. The challenge is to increase both qubit reliability and qubit scalability.

Atom Qubits vs Ion Qubits

Atoms have the potential to make powerful qubits. Unlike some other qubit contenders, such as superconducting qubits (see below), they don't rely on humans to manufacture them. Dr Tim Ballance, Lead Scientist at ColdQuanta UK, the Oxford-based quantum technology company, explains:

"Atoms have perfect manufacturing tolerances… a Caesium atom qubit in the UK is identical to one anywhere else in the world"

Nature does the job perfectly for us, with no manufacturing errors! Atom qubits have perfect reproducibility, long lifetimes, and good controllability with lasers. The fact that the atoms are neutral and are not positively charged (ions) also has significant benefits, says Dr Balance. Because ion qubits are charged they can be easily handled using electric fields to keep them in place, however this brings problems:

"The problem is that the same charge causes one qubit to repel all of the other qubits…"

This puts a limit on the number of ion qubits to about 50 ions or so for a quantum processor core.

"Neutral atoms don't have this problem, and scaling up to cores with 1000 atoms or so is quite realistic…"
The prospects for developing scalable quantum computation based on neutral atom qubits with strong entanglement look promising, and ColdQuanta are pressing ahead with development. That said, others are looking very seriously at ion-based qubit systems which have already achieved notable successes.

Not the only game in town…

Though not considered by the DISCOVERY program, so-called superconducting qubits are also leading candidates in the race to build a quantum computer.

Superconducting qubits use tiny superconducting circuits with the necessary quantum properties, and have sufficiently high controllability and low noise to be a viable candidate for medium and large-scale quantum computing known as "noisy intermediate-scale quantum" (NISQ) computing. Multi-qubit systems with 10 - 20 qubits have been demonstrated and even larger systems with 50 - 100 qubits are in development.

Because superconducting qubit circuits are manufactured using a fabrication process involving lithographic patterning, metal deposition, etching, etc. of thin films of a superconductor, the scaling up of this technology can be accelerated by leveraging techniques and materials compatible with existing silicon CMOS manufacturing. This makes them an attractive option.

That said, nobody yet really proposes to go it alone with a single qubit type. Every approach needs refining before quantum computers can be scaled up. Superconductor qubits are scalable but need to be manufactured with more consistency. Ion qubits and atom qubits systems don't have the same consistency issues but need to operate faster and be more compact. The partnerships that the DISCOVERY program will foster will not only be key to solving these problems, but should help build a robust national quantum ecosystem in the UK between academia, national labs and industry. Indeed, another core objective of DISCOVERY program is to develop the wider UK quantum-computing sector, and the program will also support establishing commercial hardware supply and roadmaps for industrial deployment of these technologies.

Some commentators suggest that a future quantum computer could simply be a hybrid of qubit types. Fast superconducting qubits might be used to run algorithms in the quantum processor core, while output from the core is photonically transferred to a more stable atom qubit or ion qubit memory store.

Once reached, commercial quantum computers could speed up scientific discovery in ways that normal computers just can't manage, from designing new green technology, such as batteries and materials, to better medicines and medical sensors, to better global navigation systems: the potential benefits are huge. Indeed, quantum computers should speed up technological progress in computer technology itself. Quantum technologists like to joke that:

"…once we have a quantum computer, we're going to use it to design the next quantum computer."

Dr Andrew Fearnside is a senior associate attorney specialising in quantum technology at patent law firm Mewburn Ellis LLP