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Exceptional-point-based accelerometers with enhanced signal-to-noise ratio

Abstract

Exceptional points (EP) are non-Hermitian degeneracies where eigenvalues and their corresponding eigenvectors coalesce1,2,3,4. Recently, EPs have attracted attention as a means to enhance the responsivity of sensors, through the abrupt resonant detuning occurring in their proximity5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20. In many cases, however, the EP implementation is accompanied by noise enhancement, leading to the degradation of the sensor’s performance15,16,17,18,19,20. The excess noise can be of fundamental nature (owing to the eigenbasis collapse) or of technical nature associated with the amplification mechanisms utilized for the realization of EPs. Here we show, using an EP-based parity–time symmetric21,22 electromechanical accelerometer, that the enhanced technical noise can be surpassed by the enhanced responsivity to applied accelerations. The noise owing to eigenbasis collapse is mitigated by exploiting the detuning from a transmission peak degeneracy (TPD) — which forms when the sensor is weakly coupled to transmission lines — as a measure of the sensitivity. These TPDs occur at a frequency and control parameters for which the biorthogonal eigenbasis is still complete and are distinct from the EPs of the parity–time symmetric sensor. Our device shows a threefold signal-to-noise-ratio enhancement compared with configurations for which the system operates away from the TPD.

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Fig. 1: \(\boldsymbol{\mathscr{P}}\boldsymbol{\mathscr{T}}\)-symmetric platform for enhanced acceleration sensing.
Fig. 2: Experimentally measured response of the sensor to applied acceleration.
Fig. 3: Measured Allan deviation.

Data availability

The datasets generated during and/or analysed during the current study are available in the Zenodo repository at https://doi.org/10.5281/zenodo.6397748.

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Acknowledgements

We acknowledge partial support from NSF-CMMI-1925543, NSF-CMMI-1925530, ONR N00014-19-1-2480 and from a grant from Simons Foundation for Collaboration in MPS number 733698. R.T. and J.C. acknowledge the partial support for this research provided by the University of Wisconsin-Madison, Office of the Vice Chancellor for Research and Graduate Education with funding from the Wisconsin Alumni Research Foundation.

Author information

Authors and Affiliations

Authors

Contributions

R.K., J.C., F.E. and R.T. designed the mechanical device. R.K. and F.E. designed and fabricated the electronic circuit. J.C. and R.T. fabricated the mechanical device. R.K. performed the characterization and data processing of the accelerometer and developed the theory with the support of T.K. All authors discussed the results. T.K. conceived the project. R.K. and T.K. wrote the manuscript with input from all authors.

Corresponding author

Correspondence to Tsampikos Kottos.

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Competing interests

The authors declare no competing interests.

Peer review

Peer review information

Nature thanks Jan Wiersig and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Extended data figures and tables

Extended Data Fig. 1 Schematic of the circuit diagram.

The dark grey large boxes indicate the ADA4862- 3 operational amplifiers, while the light grey box indicates the spring mass which provides the acceleration dependent capacitance \({C}_{{cv}}\).

Extended Data Fig. 2 Details of the mechanical sensor elements.

a,b, Drawings of the copper platform. c,d, Drawings of the test mass.

Extended Data Fig. 3 Assembly process of the acceleration capacitive sensor.

a, Deposition of the gold nanofilms on a glass substrate that create conductive electrodes which form the capac- itors plates. Attachment of the glass plates to the stationary platform and test mass. b, Placement of the test mass with glass plate on top of the copper base. c, Assembled capacitive inertial sensor. The inset shows the magnified view of the area between the capacitor plates which is about 20 m.

Supplementary information

Supplementary Information

This file contains Supplementary text, figures, equations and references.

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Kononchuk, R., Cai, J., Ellis, F. et al. Exceptional-point-based accelerometers with enhanced signal-to-noise ratio. Nature 607, 697–702 (2022). https://doi.org/10.1038/s41586-022-04904-w

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