Computing is entering a new era where the laws of quantum physics take precedence over the classical mechanics and the ensuing logic that has governed the first wave of computing, writes Dr. Mark Jackson, Senior Quantum Evangelist, and event speaker at BCS Canada.

Quantum physics plays a role in classical computing, of course, governing the behaviour of semiconductors. Yet for most professionals, these quantum effects can be discounted, having little impact on the day-to-day work of a software developer, systems integrator or security architect.

This changes in the era of quantum computing. A capacity to understand and use quantum information theory will become an asset as quantum computers become commercial. As in the classical era, the fundamental science may be hidden by abstraction, but a grasp of quantum theory will be an advantage for the quantum-ready IT professional.

Thankfully, alongside the incredible science and engineering that is making quantum computers a reality, work is already being done to make quantum theory accessible to all. This will be one of the most important contributions of UK computer scientists as we enter the quantum era.

Quantum computing is here

Echoing the birth of classical computing, the development of quantum computing began with multidisciplinary research in university physics, maths and computer science departments.

Early pioneers in the United States, Europe and the United Kingdom conceived and then built foundations that have subsequently been extended out by industrial innovators. Many of the leading quantum computing companies, such as IBM, Google, Amazon or Quantinuum have well-documented roadmaps showing how they will tackle the engineering challenges that lie ahead.

There is now a high level of confidence that today’s technology, which is often described as ‘noisy’, will soon offer advantages in certain domains such as molecular and materials science, even before issues of ‘noise’ or ‘error’ are resolved. The arrival of universal fault tolerant (UFT) quantum computers may be some way off, but applications offering economic and commercial benefit are likely to arrive years before we reach that threshold.

As in the classical domain, UK and UK-based computer scientists continue to play a leading role in the development of hardware, software and the scientific foundations. And as before, the role of trusted IT professionals will be vital to the adoption by businesses of these new technologies.

Nevertheless, the lessons of the classical era do not offer a perfect guide to the road ahead. There are important differences in the way quantum computing has developed, which distinguish it from the emergence of classical computing. For one, quantum computing is less well-defined than classical was at a similar stage of its development. There are completely different architectures, each bringing different engineering challenges and computational models.

Different modalities may succeed in different domains and produce tools that will be designed to operate in concert with classical computers. All of which, we could argue, will make the role of the quantum IT professional far more important and diverse even than the role computing professionals have played in the general adoption of classical computing.

What does a quantum IT professional need to know?

Aside from the well-trodden path of describing quantum computers in terms of concepts such as superposition, entanglement and interference, the most important thing a quantum IT professional needs to know is that quantum computers are built using quantum bits, or qubits.

There are many types of qubit, such as trapped ions, superconducting circuits or photons. Each has its advantages and disadvantages, such as greater entanglement or longer coherence times (before they succumb to errors). It is too early to declare one approach or another a winner, and it may be that multiple approaches succeed for different applications.

Quantum computing teams have developed techniques to control these qubits and use them for computation. The quantum effects of the qubits are the central feature of the operations in a quantum computer. By encoding the right type of problem in such a way that it takes advantage of these quantum effects, a system of qubits may, under the right conditions, produce a result.

Where quantum computers may excel

Much of the research in quantum computing today goes into understanding the problems quantum computers may be best suited to solving. Two classes are known: quantum systems such as chemical processes, and complex high-dimensional mathematical problems, such as combinatorial optimisation.

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Physics and chemistry simulations were among the earliest applications identified for quantum computers. Nobel Laureate Richard Feynman noted that simulating quantum systems would prove to be intractable on standard computers. He proposed using a quantum computer: ‘Nature isn't classical, dammit, and if you want to make a simulation of nature, you'd better make it quantum mechanical.’

Accurate modelling of highly correlated molecular systems, which is impossible on today’s classical computers, could support scientific progress in fields such as battery technology, semiconductors and pharmaceuticals.

Simulating such systems could bring planetary-scale benefits. A better understanding of the nitrogen fixing process, for example, might yield radical new methods for fertilizer and food production. Fertilizer production today is estimated to account for as much as 5% of global energy use.

Algorithmic speed-ups have been demonstrated in other domains, such as supply chain optimisation, machine learning and financial modelling. In cybersecurity, it is known that one of the first quantum algorithms, discovered by Peter Shor, will break the most common encryption standards in use today. There are now many proposed quantum-resilient solutions, including some that derive their strength in part by using today’s quantum computers.

Accessibility and the quantum IT professional

In 2004, Samson Abramsky and my colleague Bob Coecke at the University of Oxford published a seminal paper on categorical quantum mechanics.

Like the foundational work in the early days of classical computing, this paper drew on a wide range of scientific traditions, encompassing logic and quantum physics, category theory and semantics. Their paper remains the most-cited paper at the annual LiCS conference and was the precursor to the development of a new formalism for reasoning in quantum mechanics, known as ZX calculus.

ZX calculus abstracts away the complex and unintuitive mathematics traditionally used in quantum physics. It uses pictures to represent complex tensors and makes them easy and intuitive to manipulate and has been adopted by a growing number of quantum computing companies and university-based quantum researchers, as it provides an accessible way for developers and engineers to write and optimise quantum circuits and error correction methods.

TKET is an example of a practical tool that shares some of the same theoretical roots as ZX and has been developed as an open-source quantum software development kit by Quantinuum. TKET is now downloaded tens of thousands of times per month by people all over the world who have chosen to become acquainted with quantum computing.

Using ZX calculus, TKET and other development tools such as Qiskit, and with access to quantum computers offered by companies like IBM, Amazon and Microsoft, the door is now open for anyone working in IT today to take their first step to becoming part of the workforce of the future.

We are entering the era of the quantum IT professional.

For anyone working in computing with an interest in becoming acquainted with quantum computing, TKET is available at this Github repository.