Japan-U.S.-Canada research simulates the distribution of defects with results consistent with quantum phase transition theory

A research team led by Specially Appointed Professor Hidetoshi Nishimori of the Quantum Computing Unit, International Research Frontiers Initiative, Tokyo Institute of Technology, in collaboration with D-Wave Quantum Inc. of Canada, Saitama Medical University, and the University of Southern California, has simulated the distribution of defects in a material using D-Wave's quantum annealing device, and succeeded in obtaining results that are almost perfectly consistent with the theory of quantum phase transitions under ideal noise-free conditions.

The research team performed quantum simulations by quantum annealing on time variations in the number of defects in a material due to quantum phase transitions in one-dimensional materials. Specifically, an artificial quantum system with 2,000 qubits arranged in one dimension was implemented on a quantum annealing device, and the number of defects in it was measured at different experimental times. The results of this quantum simulation were in almost perfect agreement with the predictions of the theory of quantum phase transitions, assuming a noise-free ideal environment. This is the first example of a large-scale superconducting artificial quantum system with thousands of qubits and variable connections between qubits that can operate according to quantum mechanical theory without the influence of noise from the environment.

"An important goal moving forward is to verify quantum physics theories that have been difficult to test with classical computers and to discover new physical phenomena," explains Nishimori. "We also expect that we will need high-quality solutions to combinatorial optimization problems that are free from the effects of noise and anticipate that research and development and demonstration experiments will be conducted to solve many optimization problems in the real world with high speed and accuracy."

■ D-Wave Quantum Inc.: A Canadian company that develops and markets equipment that implements quantum annealing.

■ Quantum annealing: A method of finding the minimum value of a certain function using the effects of quantum mechanics. It is also used for quantum simulations. In 1998, Tadashi Kadowaki of the Tokyo Institute of Technology (now at Denso) and Professor Nishimori presented the basic theory, and in 2011, D-Wave commercialized the hardware.