As the rivalry between quantum and classical computing intensifies, scientists are making unexpected discoveries about quantum systems.

Classical computers outperformed a quantum computer in simulations of a two-dimensional quantum magnet system, showing unexpected confinement phenomena. This discovery by Flatiron Institute researchers redefines the practical limits of quantum computing and enhances understanding of quantum-classical computational boundaries.

Earlier this year, researchers at the Flatiron Institute’s Center for Computational Quantum Physics (CCQ) announced that they had successfully used a classical computer and sophisticated mathematical models to thoroughly outperform a quantum computer at a task that some thought only quantum computers could solve.

Now, those researchers have determined why they were able to trounce the quantum computer at its own game. Their answer, presented on October 29 in Physical Review Letters, reveals that the quantum problem they tackled — involving a particular two-dimensional quantum system of flipping magnets — displays a behavior known as confinement. This behavior had previously been seen in quantum condensed matter physics only in one-dimensional systems.

This unexpected finding is helping scientists better understand the line dividing the abilities of quantum and classical computers and provides a framework for testing new quantum simulations, says lead author Joseph Tindall, a research fellow at the CCQ.

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