Researchers at the University of Science and Technology of China have successfully observed a new class of energy-level degeneracies, known as Dirac exceptional points. This discovery opens up exciting possibilities for studying non-Hermitian dynamics and developing protocols to control quantum systems.
Dirac exceptional points are unique features that occur in non-Hermitian systems, where two different physical concepts blend together. Building on recent theoretical studies, the researchers set out to experimentally observe this type of degeneracy, which was first proposed over a century ago.
The team used nitrogen-vacancy defects in diamond as atomic-scale quantum systems within a solid-state material. They created a non-Hermitian Hamiltonian that hosted Dirac exceptional points by introducing a spin-squared operator term into a three-level system. The existence of Dirac exceptional points was confirmed by observing real eigenvalues near the degeneracy and eigenstate degeneracy at the point itself.
The discovery of Dirac exceptional points has significant implications for understanding non-Hermitian dynamics and developing new approaches to controlling quantum states. Unlike typical exceptional points, which are accompanied by complex eigenvalues, Dirac exceptional points exhibit a unique real-valued eigenvalue spectrum in their vicinity. This characteristic enables adiabatic evolution in non-Hermitian systems while overcoming dissipative effects.
The researchers hope that their study will spark further advances in the field of non-Hermitian and quantum physics. Their experimental observation of Dirac exceptional points could provide a promising avenue for achieving greater control over various cutting-edge quantum technologies, including quantum sensors and computers.
Source: https://phys.org/news/2025-04-experimental-dirac-exceptional.html