Scientists have used a quantum computer to conduct large-scale simulations of two types of quantum materials. These studies involved about 2,000 quantum bits, or qubits — many more than the tens of qubits available in most quantum computers.
The results, published in two recent studies in Science and Nature, provide a new realization of the vision of physicist Richard Feynman, who hoped to use quantum computers — rather than computers based on standard, or classical, physics — to simulate quantum systems and study their behavior. “Nature isn’t classical, dammit, and if you want to make a simulation of nature, you’d better make it quantum mechanical,” he famously said in 1981.
Performed on a computer built by D-Wave Systems Inc. of Burnaby, Canada, the simulations provide a way to study phenomena that are very difficult to replicate with classical computers. “These are really rather beautiful pieces of science,” says physicist Seth Lloyd of MIT. The researchers are “able to reproduce all kinds of predicted phenomena.”
D-Wave’s machines, however, have attracted skepticism, and some physicists are not convinced of the importance of the new results.
In a study published August 22 in Nature, D-Wave physicists describe simulating the physics of a two-dimensional magnetic material, identifying a transition in which whirlpoollike defects known as vortices pair up in the material when the temperature drops. The theoretical prediction of this phase transition won the 2016 Nobel Prize in physics, and the phenomenon is relevant to the physics of superconductors, materials that transmit electricity without resistance at low temperatures (SN: 10/29/16, p. 6). The simulation’s results matched the output of simulations performed on classical computers.
Another simulation, reported July 13 in Science, replicated the behavior of a 3-D material that transitioned between different magnetic phases when the researchers changed variables such as an applied magnetic field. The observed phases included a disordered state known as a spin glass.