# Measuring the knot of non-Hermitian degeneracies and non-commuting braids.

@article{Patil2022MeasuringTK, title={Measuring the knot of non-Hermitian degeneracies and non-commuting braids.}, author={Yogesh S S Patil and Judith H{\"o}ller and Parker A Henry and Chitres Guria and Yiming Zhang and Luyao Jiang and Nenad Kralj and Nicholas Read and Jack G E Harris}, journal={Nature}, year={2022}, volume={607 7918}, pages={ 271-275 } }

Any system of coupled oscillators may be characterized by its spectrum of resonance frequencies (or eigenfrequencies), which can be tuned by varying the system's parameters. The relationship between control parameters and the eigenfrequency spectrum is central to a range of applications1-3. However, fundamental aspects of this relationship remain poorly understood. For example, if the controls are varied along a path that returns to its starting point (that is, around a 'loop'), the system's…

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