I was at a conference in Grenoble last year. Apart from the science, this was most memorable for the “cultural activity”: laserquest. When it came to picking teams, some bright spark suggested “physicists vs computer scientists”. Immediate shuffling on the part of most people, and then something interesting happened. We had people hesitating in the middle, unsure of which side to go to. General consensus sorted them out, and then objections were raised to some of those who had chosen immediately; “come on, of course you’re a computer scientist!” was one comment to a self-proclaimed physicist, who subsequently switched sides. I stayed and played, unchallenged, on the physics team (we lost). Back in the UK I started to tell colleagues the story, smug in my existential physics-ness, to be met with a curious gaze and the blunt question, “so which team did you play for?”.
It’s not just physics and computer science, of course. Quantum computing is a strange city, inhabiting multiple spaces. Mathematics, engineering, philosophy, and even some new tentative forays into biology. It’s a two-way process: you only have to think about how quantum computing has changed the way quantum mechanics is taught in undergraduate physics courses to see the back-reaction at work. Quantum computing and information theory has added a whole new arsenal of tools to theoretical computer science; driven advances in, for example, category theory; been the impetus behind developing semiconductor and nanophotonic technologies; and helped redefine concepts of information and knowledge of physical systems.
But what if you want to go the other way – what if you want to work on quantum computing itself, not just on how it interacts with and reflects back on one particular academic discipline? What determines whether that is physics, computer science, maths… ? Perhaps it’s the questions that are asked, that some questions are fundamentally “physics” questions, and so on. Or perhaps it’s the tools used to answer the questions – if you use computer science tools such as complexity theory then of course you’re doing computer science. Or is it a function of the background of the researcher? If the researcher is in a mathematics department then as a matter of course their research is mathematics…
The problem is, while the distinctions between the fields are clear in a lot of cases, quantum computing by its very nature sits on the cracks in the pavement. Building a quantum computer, programming it, knowing what it is capable of, this requires knowledge, skills and people from all these different areas. Often questions don’t play fair, don’t sit easily in one subject or another. For example, if we’re to design a repeater network as physicists, do we work out an interlink possibility then throw our hands in the air and say “I’m not going to look at how the links are composed, that doesn’t have a Hamiltonian in it so it’s not my business”? Of course not, because how we want to propagate information through the network determines the best physical link mechanism to use.
I say “of course not”, but yet that seems to be the norm of what actually happens. Physicists, computer scientists, engineers… , all wandering around Besźel and Ul Qoma, occupying the same problem space but studiously “unseeing” the landscape of the other fields. Designated cross-over points, generally conferences, are allowed, but try to do that in your everyday research and you’re soon in trouble. Which journals do you publish in? If you’re in a physics department, do your computer science publications count for the RAE? (answer: no). Who do you apply for jobs with? If you get a job in that department, how much does that restrict where you apply next? (answer: a lot). Who do you apply to for funding? And, looming over everything, where will you aim to get that all-important permanent position? And how much are you damaging that possibility by having a “fractured” “interdisciplinary” track record?
There are of course people who bridge the gaps between the fields, who can quite happily work with people on both sides. They all, however, tend to be established researchers with unimpeachable credentials firmly in one discipline. Perhaps that’s then the way forward – we stick dutifully to one area for a good long post-doc stretch, and at the end we’re rewarded with brownie points to go and spend on interdisciplinary projects. The problem I find is in reconciling this way of working with actually doing good science. If there’s a problem that crosses the boundaries, why not use techniques and skills from the “other” city? If the problem pushes into a crosshatched street, why not follow it? How is science served by wearing blinkers that tell us to sidestep questions that aren’t in “our” field, even though they’re directly relevant to work that we’re told is? Perhaps we could all do with a bit more Breaching of boundaries in our work – seeing the city and the city, quantum computing and quantum computing.