**(R&DMag)** Heidelberg University physicist Dr. Philipp Hauke and colleagues from Dresden and Innsbruck (Austria) have demonstrated that digital quantum simulations can be more “robust” and hence much more stable than previously assumed.

Calculations using conventional computers require resources that increase exponentially with the number of constituent quantum particles. Digital quantum simulation provides one possible workaround. The nonequilibrium dynamics are studied with simulators that themselves are governed by quantum-mechanical laws.

“A simulation that can predict the behaviour of many quantum particles over a longer time therefore becomes more and more likely. This further opens the door for practical applications, ranging from materials science and quantum chemistry to issues in fundamental physics,” states Hauke, who heads the “Quantum optics and quantum many-body theory” research group.

Using numerical demonstrations and analytical arguments, the researchers have now shown that quantum simulation is much more “robust” and hence more stable than previously assumed, as long as only values that are relevant in practice—such as averages across the entire system—are considered and not the full state of each individual particle. For such values, there is a sharp threshold between a region with controllable errors and a simulation that can no longer deliver a usable result.