  We present QuantumSync, the first quantum algorithm for solving a
synchronization problem in the context of computer vision. In particular, we
focus on permutation synchronization which involves solving a non-convex
optimization problem in discrete variables. We start by formulating
synchronization into a quadratic unconstrained binary optimization problem
(QUBO). While such formulation respects the binary nature of the problem,
ensuring that the result is a set of permutations requires extra care. Hence,
we: (i) show how to insert permutation constraints into a QUBO problem and (ii)
solve the constrained QUBO problem on the current generation of the adiabatic
quantum computers D-Wave. Thanks to the quantum annealing, we guarantee global
optimality with high probability while sampling the energy landscape to yield
confidence estimates. Our proof-of-concepts realization on the adiabatic D-Wave
computer demonstrates that quantum machines offer a promising way to solve the
prevalent yet difficult synchronization problems.
