Non-Hermiticity can lead to the emergence of many intriguing phenomena that are absent in Hermitian systems,enabled by exceptional topological defects,among which Weyl exceptional rings(WER)are particularly interestin...Non-Hermiticity can lead to the emergence of many intriguing phenomena that are absent in Hermitian systems,enabled by exceptional topological defects,among which Weyl exceptional rings(WER)are particularly interesting.The topology of a WER can be characterized by the quantized Berry phase and a nonzero Chern number,both encoded in the eigenvectors of the non-Hermitian Hamiltonian.So far,WERs have been realized with classical wave systems,whose eigenvectors can be well described by classical physics.We here report the first quantum-mechanical implementation of WERs and investigate the related topology transitions.The experiment system consists of a superconducting qubit and a dissipative resonator,coupled to each other.The high flexibility of the system enables us to characterize its eigenvectors on different manifolds of parameter space,each of which corresponds to a quantum-mechanical entangled state.We extract both the quantized Berry phase and Chern number from these eigenvectors,and demonstrate the topological transition triggered by shrinking the size of the corresponding loop or manifold in parameter space.展开更多
Non-Hermitian(NH)systems can display exceptional topological defects without Hermitian counterparts,exemplified by exceptional rings in NH two-dimensional systems.However,exceptional topological features associated wi...Non-Hermitian(NH)systems can display exceptional topological defects without Hermitian counterparts,exemplified by exceptional rings in NH two-dimensional systems.However,exceptional topological features associated with higher-dimensional topological defects have only recently come into attention.We here investigate the topology of the singularities in an NH threedimensional system.We find that the third-order singularities in the parameter space form an exceptional surface(ES),on which all three eigenstates and eigenenergies coalesce.Such an ES corresponds to a two-dimensional extension of a point-like synthetic tensor monopole.We quantify its topology with the Dixmier-Douady invariant,which measures the quantized flux associated with the synthetic tensor field.We further propose an experimentally feasible scheme for engineering such an NH model.Our results pave the way for investigations of exceptional topology associated with topological defects with more than one dimension.展开更多
基金supported by the National Natural Science Foundation of China(12274080,12474356,12475015,and U21A20436)Innovation Program for Quantum Science and Technology(2021ZD0300200 and 2021ZD0301705)。
文摘Non-Hermiticity can lead to the emergence of many intriguing phenomena that are absent in Hermitian systems,enabled by exceptional topological defects,among which Weyl exceptional rings(WER)are particularly interesting.The topology of a WER can be characterized by the quantized Berry phase and a nonzero Chern number,both encoded in the eigenvectors of the non-Hermitian Hamiltonian.So far,WERs have been realized with classical wave systems,whose eigenvectors can be well described by classical physics.We here report the first quantum-mechanical implementation of WERs and investigate the related topology transitions.The experiment system consists of a superconducting qubit and a dissipative resonator,coupled to each other.The high flexibility of the system enables us to characterize its eigenvectors on different manifolds of parameter space,each of which corresponds to a quantum-mechanical entangled state.We extract both the quantized Berry phase and Chern number from these eigenvectors,and demonstrate the topological transition triggered by shrinking the size of the corresponding loop or manifold in parameter space.
基金supported by the National Natural Science Foundation of China(Grant Nos.12474356,12475015,12274080,12204105,and 11875108)。
文摘Non-Hermitian(NH)systems can display exceptional topological defects without Hermitian counterparts,exemplified by exceptional rings in NH two-dimensional systems.However,exceptional topological features associated with higher-dimensional topological defects have only recently come into attention.We here investigate the topology of the singularities in an NH threedimensional system.We find that the third-order singularities in the parameter space form an exceptional surface(ES),on which all three eigenstates and eigenenergies coalesce.Such an ES corresponds to a two-dimensional extension of a point-like synthetic tensor monopole.We quantify its topology with the Dixmier-Douady invariant,which measures the quantized flux associated with the synthetic tensor field.We further propose an experimentally feasible scheme for engineering such an NH model.Our results pave the way for investigations of exceptional topology associated with topological defects with more than one dimension.
