Finally out of stealth mode: a plea for Quantum Foundations
A personal account on the 2022 Physics Nobel prize
By Prof Bob Coecke, Chief Scientist and Head of Compositional Intelligence, Quantinuum
Although this year’s Nobel prize was announced by the committee as an award in the field of Quantum Information, it was in fact one of the most significant physics prizes ever awarded and in many respects was as much a prize in Quantum Foundations as anything else. Inspired by Einstein, von Neumann (the father of the modern computer), and of course Schrödinger, Quantum Foundations concerns itself with the very heart of quantum physics. More specifically, this year’s Nobel prize was really about the recognition of the existence of entanglement/non-locality, both in terms of its theoretical underpinnings, as well as its experimental verification.
In order to understand why this year’s prize is of such great importance, one needs to travel back to the previous century. At the time that Nobel laureate Anton Zeilinger did his award-winning research, there were very few advanced academic research or faculty positions at any level in Quantum Foundations in university physics or maths departments. Some worked on these matters in philosophy departments, and then there was Zeilinger’s own group in Vienna. The fact is that that the large majority of physicists at the time considered Quantum Foundations to be a marginal (at best) endeavour, preferring to work under the well-known slogan, “shut up and calculate!” As a serious research area, Quantum Foundations was considered as being mainly of philosophical interest, with no prospect of progress of any kind for any serious scientist. Many of the very brightest young physics researchers that were attracted to the field were forced to leave academia.
The field that we now call Quantum Information, which is driving the Quantum Technology revolution, has its roots in Quantum Foundations. For some 20 years now, by “hiding” under the banner of Quantum Information, a few more Quantum Foundations groups have come into being, but even then, typically not in physics departments. In fact, I was the first Professor of Quantum Foundations, and my appointment was to the computer science department at Oxford University. The second such position, not entirely surprisingly, was Caslav Brukner in Anton Zeilinger’s group.
With this Nobel prize, the physics community has finally caught up with Quantum Foundations.
Quantum theory, post Schrodinger-Bell-Clauser-Aspect-Zeilinger
The group I led at Oxford University embraced the fact that Quantum Information Theory and the use of Quantum Technologies is very much a product of Quantum Foundations. It is exactly this stance that enabled us to be at the cutting edge of the field. This approach is reflected in much of the work that we do today at Quantinuum, and which is done in other research led institutions involved with quantum computing.
It is worth taking a moment to recognise how much progress in Quantum Foundations has been held up by disagreements among quantum physicists. There has been a deep discomfort by many university-based researchers with quantum theory’s deviating from the “traditional” worldview.
This debate has dominated Quantum Foundations, leaving no space for a programme to radically reshape quantum theory by embracing entanglement/non-locality. This has been compounded by the typical conservatism of the physics community, about which the originator of quantum theory Max Planck once said: “Science advances one funeral at a time. A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
My own research, and the work of many of my colleagues, follows Schrödinger’s view that entanglement/non-locality “are not just a, but rather the characteristic feature of quantum theory”. We embraced entanglement/non-locality as a first-class citizen when, almost 20 years ago, we gave quantum theory an entirely new look. We drew on the principles of category theory to produce a new, highly expressive formalism called Categorical Quantum Mechanics (CQM). The need for a new look for quantum theory was first demanded by von Neumann, a mere three years after the publication of the old quantum theory, in 1932.’
In its most recent form, CQM has become a graphical theory, and the book, Picturing Quantum Processes, which I co-authored with Aleks Kissinger, has become a standard text for many studying or working in quantum computing. A part of CQM called ZX calculus is now well-known and widely used within the quantum industry by most of the leading firms developing Quantum Technologies.
But CQM had to be developed in stealth mode, by presenting it as high-level quantum programming. Under that umbrella we were able to build the largest Quantum Foundations group in the world, which we got away with by being in a computer science department. The respect for our work by existing Quantum Foundations teams such as Zeilinger’s group in Vienna and the then newly founded Perimeter Institute was also very important. Being at Oxford University and having world-leaders in computer science like Samson Abramsky involved in the development of CQM has played a huge role. It is fair to say that these two institutions and our group have been the pillars on which the new Quantum Foundations community has developed.
Quantum Foundations in Quantum Industry
It is my view that many governmental funding bodies are letting foundational work down again by directing excessive resources to research projects based on their ability to show “short term” impact. The sad reality is that for many founding fathers of Quantum Information like David Deutsch, their pioneering research would today not be possible. Hopefully this year’s physics Nobel prize may change that, as long as we all keep making the case loudly enough that Quantum Information and hence Quantum Technology is very much a product of Quantum Foundations.
When Quantinuum embraced our way of conceiving quantum theory, it was a sign of a shift in the locus of Quantum Foundations from academia towards industry. Many of us have chosen to pursue our research in firms that value Quantum Foundations, leaving behind us forever the need to work in stealth mode.
Today, ZX calculus has become the beating heart of Quantinuum’s TKET-compiler — one of the reasons it performs so efficiently. CQM has made possible the discovery of quantum-native natural language processing, a field where AI truly goes hand-in-hand with quantum theory, and takes important inspiration from it in the form of “compositionality”. And the number of scientific papers published with reference to ZX calculus continues to grow exponentially, and so does the number of firms using it.
But technology is not where this story ends. Besides technology we also need the broader world to get familiar with the new quantum realm that increasingly will become part of our lives. We need to recover our appetite for learning what quantum observations tell us about the way the world works. We need to prepare for Quantum Foundations to occupy a place much closer to the heart of things.
To help us prepare for this quantum future, we are in the process of finalising a book that will be accessible for members of the public, and which was partially designed to be understood by High School students. It will provide readers with the true face of quantum theory by going straight to its entangled and non-local heart, just as Schrödinger predicted. The title of this book will be Quantum in Pictures.
