# Asymmetric balance in symmetry breaking

## TL;DR

This paper experimentally demonstrates that introducing a second controllable asymmetry can restore features of spontaneous symmetry breaking destroyed by a single asymmetry, revealing that asymmetries can balance each other and offering new practical applications.

## Contribution

It is the first experimental study of two controllable asymmetries in symmetry breaking, showing how they can balance each other to restore symmetry-breaking features.

## Key findings

- Features of spontaneous symmetry breaking can be restored by a second asymmetry.
- Asymmetries can be exploited as an additional degree of freedom.
- First observation of polarization symmetry breaking in passive driven nonlinear resonators.

## Abstract

Spontaneous symmetry breaking is central to our understanding of physics and explains many natural phenomena, from cosmic scales to subatomic particles. Its use for applications requires devices with a high level of symmetry, but engineered systems are always imperfect. Surprisingly, the impact of such imperfections has barely been studied, and restricted to a single asymmetry. Here, we experimentally study spontaneous symmetry breaking with two controllable asymmetries. We remarkably find that features typical of spontaneous symmetry breaking, while destroyed by one asymmetry, can be restored by introducing a second asymmetry. In essence, asymmetries are found to balance each other. Our study illustrates aspects of the universal unfolding of the pitchfork bifurcation, and provides new insights into a key fundamental process. It also has practical implications, showing that asymmetry can be exploited as an additional degree of freedom. In particular, it would enable sensors based on symmetry breaking or exceptional points to reach divergent sensitivity even in presence of imperfections. Our experimental implementation built around an optical fiber ring additionally constitutes the first observation of the polarization symmetry breaking of passive driven nonlinear resonators.