Spontaneous Symmetry Breaking of an Optical Polarization State in a Polarization-Selective Nonlinear Resonator

TL;DR

This paper demonstrates spontaneous symmetry breaking and bistability in optical polarization states using atomic rubidium vapor, with potential applications in optical Ising machines for solving complex optimization problems.

Contribution

It introduces a novel mechanism leveraging polarization self-rotation and feedback in a resonator to induce symmetry breaking and bistability, enabling optical simulation of Ising models.

Findings

Observation of polarization symmetry breaking in rubidium vapor

Bistable polarization patterns due to vacuum fluctuations

Proposal for optical Ising machine implementation

Abstract

We exploit polarization self-rotation in atomic rubidium vapor to observe spontaneous symmetry breaking and bistability of polarization patterns. We pump the vapor cell with horizontally polarized light while the vertical polarization, which is initially in the vacuum state, is resonated in a ring cavity. Vacuum fluctuations in this mode experience cumulative gain due to the compound action of amplification due to the self-rotation and feedback through the resonator, eventually acquiring a macroscopic magnitude akin to an optical parametric oscillator. The randomness of these fluctuations results in a bistable, random macroscopic polarization pattern at the output. We propose utilizing this mechanism to simulate Ising-like interaction between multiple spatial modes and as a basis for a fully optical coherent Ising machine.