Quantum annealing of the Traveling Salesman Problem

We propose a path-integral Monte Carlo quantum annealing scheme for the symmetric Traveling Salesman Problem, based on a highly constrained Ising-like representation, and we compare its performance against standard thermal Simulated Annealing. The Monte Carlo moves implemented are standard, and consist in restructuring a tour by exchanging two links (2-opt moves). The quantum annealing scheme, even with a drastically simple form of kinetic energy, appears definitely superior to the classical one, when tested on a 1002 city instance of the standard TSPLIB.