Quantum annealing

Quantum annealing is an optimization process for finding the global minimum of an objective function over a set of candidate solutions by using quantum fluctuations. It is used mainly where the search space is discrete and has many local minima, such as finding the ground state of a spin glass or solving QUBO problems that can encode Max-Cut, graph coloring, satisfiability or the traveling salesman problem. The term was first proposed in 1988 by Apolloni, Cesa Bianchi and De Falco as a quantum-inspired classical algorithm, and it took its present form in 1998 with Kadowaki and Nishimori. The system starts in a superposition of all candidate states and evolves under the time-dependent Schrodinger equation while a transverse field is switched off, so quantum tunneling carries it toward the ground state that encodes the answer.