In quantum annealing, a system with two non-commuting time dependent interactions is slowly evolved from an initial trivial state to a final complex classical state. If the evolution is slow enough, the final state can represent the solution of a difficult optimization  problem encoded in the Hamiltonian. Practical implementations of quantum annealing are limited by short coherence times, however, and there are also still  fundamental questions about the speedup that can be achieved relative to classical optimization. I will discuss  experiments [1] on a device with more than 5000 programmable superconducting qubits (the D-Wave Advantage system) with couplings programmed to one of the prototypical hard optimization problems - the 3D Ising spin glass.  While the coherence times are not long enough to reach the ground state, the results and comparisons with numerical simulations show that the system traverses the spin glass transition, and the final state reached for different system sizes and annealing times correctly reproduces expectations from scaling theory. The state of the art is now approaching the point where quantum annealing can address problems beyond the reach of classical computers.
 

 [1] A. King et al., Nature 617, 61 (2023).
 

Anders Sandvik is a Professor of Physics at Boston University and a Visiting Professor of the Institute of Physics of the Chinese Academy of Sciences in Beijing. He completed his PhD at the University of California, Santa Barbara, in 1993, then carried out postdoctoral work at Florida State University and the University of Illinois at Urbana-Champaign before returning to his native country as a Senior Fellow of the Academy of Finland in 2000. He joined the faculty of Boston University in 2004. He is a Fellow of the American Physical Society, a Simons Investigator in Physics, and the 2021 recipient of the Aneesur Rahman Prize for Computational Physics. His research focuses on computational studies in quantum many-body physics. He is the inventor of the Stochastic Series Expansion method and several other widely used simulation techniques. His studies of quantum lattice models have provided unique insights into collective quantum many-body states and their quantum phase transitions.

Please contact phweb@ust.hk should you have questions about the talk.