WebAssembly has come a long way from the browser; it can be used for building https://thenewstack.io/python-and-webassembly-elevating-performance-for-web-apps/, for https://thenewstack.io/webassembly/serverless-webassembly-for-browser-developers/, and for https://thenewstack.io/webassembly-5-predictions-for-2023/. Quantum computing uses https://thenewstack.io/quantum-computing-use-cases-how-viable-is-it-really/ (large, expensive and very, very cold) to model complex systems and problems that need more memory than the largest supercomputer: it stores information in equally exotic quantum states of matter and runs computations on it by controlling the interactions of subatomic particles. But alongside that futuristic quantum computer, you need traditional computing resources to feed data into the quantum system, to get the results back from it — and to manage the state of the qubits to deal with errors in those fragile quantum states.
The control system software is “preparing quantum states, doing some mid-circuit measurements, taking those mid-circuit measurements, maybe doing a little bit of classical calculation in the control system software and then passing those values to the WebAssembly environment.”
In the end, esoteric as the work is, the appeal of WebAssembly for quantum computing error correction is very much what makes it so useful in so many areas.