Topological Eigenvalue Braiding and Quantum State Transfer Near a Third-Order Exceptional Point
Journal article, 2025
Non-Hermitian systems exhibit a variety of unique features rooted in the presence of exceptional points (EPs). The distinct topological structure in the proximity of an EP gives rise to counterintuitive behaviors absent in Hermitian systems, which emerge after encircling the EP either quasistatically or dynamically. However, experimental exploration of EP encirclement in quantum systems, particularly those involving high-order EPs, remains challenging due to the difficulty of coherently controlling more degrees of freedom. In this work, we experimentally investigate the eigenvalue braiding and state transfer arising from the encirclement of EP in a three-dimensional non-Hermitian quantum system using superconducting circuits. We characterize the second- and third-order EPs through the coalescence of eigenvalues. Then we reveal the topological structure near the EP3 by quasistatically encircling it along various paths with three independent parameters, which yields the eigenvalue braiding described by the braid group B3. Additionally, we observe chiral state transfer between three eigenstates under a fast driving scheme when no EPs are enclosed, while time-symmetric behavior occurs when at least one EP is encircled. Our findings offer insights into understanding non-Hermitian topological structures and the manipulation of quantum states through dynamic operations.
Author
He Zhang
Chinese Academy of Sciences
Tong Liu
Chinese Academy of Sciences
Chalmers, Microtechnology and Nanoscience (MC2), Quantum Technology
Zhongcheng Xiang
Hefei National Laboratory for Physical Sciences at Microscale
Songshan Lake Materials Laboratory
Chinese Academy of Sciences
Beijing Academy of Quantum Information Sciences
Kai Xu
Beijing Academy of Quantum Information Sciences
Hefei National Laboratory for Physical Sciences at Microscale
Songshan Lake Materials Laboratory
Chinese Academy of Sciences
Heng Fan
Chinese Academy of Sciences
Hefei National Laboratory for Physical Sciences at Microscale
Beijing Academy of Quantum Information Sciences
Songshan Lake Materials Laboratory
Dongning Zheng
Chinese Academy of Sciences
Songshan Lake Materials Laboratory
Hefei National Laboratory for Physical Sciences at Microscale
PRX Quantum
26913399 (eISSN)
Vol. 6 2 020328Subject Categories (SSIF 2025)
Condensed Matter Physics
DOI
10.1103/PRXQuantum.6.020328