We propose an algorithm inspired by optical coherent Ising machines to solve
the problem of polynomial unconstrained binary optimisation (PUBO). We
benchmark the proposed algorithm against existing PUBO algorithms on the
extended Sherrington-Kirkpatrick model and random third-degree polynomial
pseudo-Boolean functions, and observe its superior performance. We also address
instances of practically relevant computational problems such as protein
folding and electronic structure calculations with problem sizes not accessible
to existing quantum annealing devices. In particular, we successfully find the
lowest-energy conformation of lattice protein molecules containing up to eleven
amino-acids. The application of our algorithm to quantum chemistry sheds light
on the shortcomings of approximating the electronic structure problem by a PUBO
problem, which, in turn, puts into question the applicability of quantum
annealers in this context.Comment: 10 pages, 6 figure