A Major Quantum Computing Problem May Finally Have an Answer: Can We Trust the Results?

Researchers can now put numerical error limits on quantum simulations, showing how much confidence to place in their results.

As quantum simulators become powerful enough to tackle problems beyond the reach of conventional computers, a difficult question follows: how can researchers know whether their answers are accurate? When classical calculations are still possible, the two approaches can be compared directly. Once quantum systems move beyond that point, however, scientists need another way to verify the results.

Researchers led by Tristan Kraft of the Technical University of Munich and Peter Zoller of the University of Innsbruck and the Institute for Quantum Optics and Quantum Information at the Austrian Academy of Sciences, together with Barbara Kraus of the Technical University of Munich, have demonstrated a method for experimentally characterizing a quantum simulator and turning its uncertainties into numerical error limits. A team led by Manoj Joshi and Christian Roos tested the approach with an ion-trap quantum simulator containing as many as 51 ions.

Real devices introduce unavoidable uncertainty

Quantum simulators are physical systems designed to reproduce the behavior of other quantum systems. They are especially useful for studying complicated many-particle systems whose calculations can quickly become too demanding for classical computers.