Sensor-performance limitations at exceptional points

Determine the performance limitations of sensors operating at exceptional points in non-Hermitian photonic systems.

Background

Exceptional points (EPs) are non-Hermitian spectral degeneracies where eigenfrequencies and eigenmodes coalesce. EPs have been proposed for ultra-sensitive sensing applications, motivating careful quantification of feasible performance in realistic systems.

The paper develops a contour-integration and algorithmic-differentiation framework to compute eigenfrequency sensitivities near EPs, enabling analysis and optimization of EP-based devices. Within this context, the authors explicitly note that limitations affecting sensor performance at EPs remain an open problem in the field.

References

The research on EPs is still a vital field with open problems, such as sensor-performance limitations or Petermann factor divergence at EPs.

— Computing eigenfrequency sensitivities near exceptional points  (2402.17648 - Binkowski et al., 2024) in Introduction

The open problem is to turn reservoir memory into a controllable spectral resource while preserving readout fidelity and device stability.

— Exceptional Points in Photonics: From Non-Hermitian Physics to Applications  (2609.01239 - Zhang et al., 1 Sep 2026) in Section 5, subsection “Frontier directions and open questions”

The unresolved issue is therefore whether a complete quantum measurement protocol can convert spectral amplification into metrological gain after noise and discarded information are counted.

— Exceptional Points in Photonics: From Non-Hermitian Physics to Applications  (2609.01239 - Zhang et al., 1 Sep 2026) in Section 5, subsection “Frontier directions and open questions”