Reconfiguring the Order of Exceptional Points in a Scalable High‐Order Anti‐Parity‐Time Symmetric System

Abstract Exceptional points (EPs) are singularities in non‐Hermitian systems that feature as two or more eigenvalues and eigenvectors coalesce simultaneously, offering exceptional sensitivity depending on the order of EPs. Especially, in the second‐order dissipative coupling system, the eigenvalues exhibit EP shift in the presence of external perturbations or fabrication imperfections. Here, a scalable arbitrary order anti‐parity‐time (APT) symmetric system is proposed, of which the EPs experience consecutively processes of order decrease, the second‐order EP (EP2) shifts, and order increase in response to external perturbations. In a conventional coherent coupling system, EPs are completely disrupted by the perturbation, causing all eigenvalues to deviate from the EPs. On the contrary, when introducing perturbations into the proposed APT system, all eigenvalues divide into one or more pairs, with each pair forming an EP2 indicating that high‐order EPs degenerate into one or more EP2s. Counter‐intuitively, the order decrease of EPs can also exhibit an enhancement proportional to upon a perturbation in an ‐order system. Notably, one or more EP2s survive in the presence of perturbations, a distinct property making the high‐order dissipative system suitable for multiple sensing scenarios in chronological sequences. This property also warrants further exploration of EP‐related phenomena under the influence of external perturbations, with the potential to yield significant advancements in the field. These findings will inspire constructing arbitrary order EPs and the design of exceptionally sensitive sensors for real‐world applications.