I believe that quantum simulation is slated for a breakthrough by 2020 (Nature 463, 26–32; 2010). In a groundbreaking lecture (Intl J. Theor. Phys. 21, 467–488; 1982), Richard Feynman pointed out that large quantum systems are impossible to simulate with a classical computer. He proposed that they might instead be simulated with a quantum-mechanical machine — in short, a quantum simulator.

Some promising technologies have emerged, but verifying a quantum simulation is not straightforward. Do the results demonstrate properties of the simulated model, or are they due to unrelated features of the simulator? At first, this quandary seems insoluble, as the same complexity that drives one to attack the problem on a quantum simulator will thwart any attempt, whether analytical or on a regular computer, to prove the quantum-simulation result is correct.

But if the same physics models are simulated on different quantum simulators based on different technologies, it is quite likely that common features of all the results will be due to the quantum-physical model and not to the systematics of the simulators. Scientists and funders should therefore support development of as many technologies as possible.