**(PhysicsWorld)** Researchers from the Hefei National Laboratory for Physical Sciences at the University of Science and Technology of China say they have observed parity-time symmetry breaking for the first time in an experiment. The result was obtained using a “dilation” technique on a single-spin system – a nitrogen-vacancy centre in diamond. “The information we extracted from the dynamics in our system extends and deepens our understanding of quantum physics,” team leader Jiangfeng Du said.

The researchers “dilated” their system, which means they extended it to a larger system – in this case, to one that is governed by a non-classical Hermitian Hamiltonian. In quantum mechanics, a Hamiltonian is an operator describing the energy of a system. The PT symmetry and Hermitian are two mathematical terms describing the properties of Hamiltonians.