# Covert Scattering Control in Metamaterials with Non-Locally Encoded Hidden Symmetry

arXiv: https://arxiv.org/abs/2305.00906 · HTML: https://mlsanity.com/paper/2305.00906/

## Key facts

- Cited by 1 papers in the map (data through 14 Oct 2026).
- First posted on arXiv 26 Apr 2023.

## Built on by (most cited first, 1 of 1)

- [Target localization, identification and sensing using latent symmetries](https://mlsanity.com/paper/2606.01421/) (2026)

## Abstract (arXiv)

Symmetries and tunability are of fundamental importance in wave scattering control, but symmetries are often obvious upon visual inspection which constitutes a significant vulnerability of metamaterial wave devices to reverse-engineering risks. Here, we theoretically and experimentally show that it is sufficient to have a symmetry in the reduced basis of the "primary meta-atoms" that are directly connected to the outside world; meanwhile, a suitable topology of non-local interactions between them, mediated by the internal "secondary" meta-atoms, can hide the symmetry from sight in the canonical basis. We experimentally demonstrate covert symmetry-based scattering control in a cable-network metamaterial featuring a hidden parity (P) symmetry in combination with hidden-P-symmetry-preserving and hidden-P-symmetry-breaking tuning mechanisms. First, we achieve physical-layer security in wired communications, using the domain-wise hidden P-symmetry as shared secret between the sender and the legitimate receiver. Then, within the approximation of negligible absorption, we report the first tuning of a complex scattering metamaterial without mirror symmetry to feature exceptional points (EPs) of PT-symmetric reflectionless states, as well as quasi-bound states in the continuum. Finally, we show that these results can be reproduced in metamaterials involving non-reciprocal interactions between meta-atoms, including the first observation of reflectionless EPs in a non-reciprocal system.