Eur. Phys. J. Special Topics 224, 17–24 (2015)
https://doi.org/10.1140/epjst/e2015-02340-6

Review

Quantum tunneling vs. thermal effects in experiments on adiabatic quantum computing

¹ The James Franck Institute and Department of Physics, The University of Chicago, Chicago, Illinois 60637, USA
² Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, California 91125, USA
³ Departments of Physics, Swiss Federal Institutes of Technology, Zurich and Lausanne, Switzerland
⁴ Paul Scherrer Institute, Villigen, Switzerland
⁵ London Centre for Nanotechnology and Department of Physics and Astronomy, UCL, London WC1E 6BT, UK

^a e-mail: tfr@caltech.edu

Received: 19 September 2014
Revised: 16 December 2014
Published online: 5 February 2015

Abstract

Traditional simulated annealing uses thermal fluctuations for convergence in optimization problems. Quantum tunneling provides a different mechanism for moving between states, with the potential for reduced time scales and different outcomes. Thermal and quantum annealing are compared in two concentration regimes of a model disordered magnet, where the effects of quantum mechanics can be tuned both by varying an applied magnetic field and by controlling the strength of thermal coupling between the magnet and an external heat bath. The results indicate that quantum annealing hastens convergence to the final state, and that the quantum character of the final state can be engineered thermodynamically.