**(EurekaAlert)** Researchers have observed a break in a single quantum system for the first time. The observation has potential implications for physics beyond the standard understanding of how quantum particles interact to produce matter and allow the world to function as we know it.

Called Parity-Time (PT) Symmetry, the mathematical term describes the properties of a quantum system–the evolution of time for a quantum particle, as well as if the particle is even or odd. Whether the particle moves forward or backward in time, the state of oddness or evenness remains the same in the balanced system. When the parity changes, the balance of system — the symmetry of the system — breaks.

In order to better understand quantum interactions and develop next-generation devices, researchers must be able to control the symmetry of systems. If they can break the symmetry, they could manipulate the spin state of the quantum particles as they interact, resulting in controlled and predicted outcomes. “Our work is about that quantum control,” said Yang Wu, an author on the paper and a PhD student in the Hefei National Laboratory for Physical Sciences at the Microscale and Department of Modern Physics at the University of Science and Technology of China.