On-demand Parity-Time symmetry in a lone oscillator through complex, synthetic gauge fields

TL;DR

This paper demonstrates a method to implement and control parity-time symmetry in a single, tunable LC oscillator using synthetic gauge fields, revealing PT transitions and exceptional point phenomena.

Contribution

It introduces a novel protocol for achieving on-demand PT symmetry in a lone oscillator through synthetic gauge fields, enabling dynamic control of gain-loss profiles.

Findings

Observation of static and Floquet PT breaking transitions.

Detection of conserved quantities in the gain-loss system.

Unveiling of giant dynamical asymmetry along exceptional point contours.

Abstract

What is the fate of an oscillator when its inductance and capacitance are varied while its frequency is kept constant? Inspired by this question, we propose a protocol to implement parity-time (PT) symmetry in a lone oscillator. Different forms of constrained variations lead to static, periodic, or arbitrary balanced gain and loss profiles, that can be interpreted as purely imaginary gauge fields. With a state-of-the-art, dynamically tunable LC oscillator comprising synthetic circuit elements, we demonstrate static and Floquet PT breaking transitions, including those at vanishingly small gain and loss, by tracking the circuit energy. Concurrently, we derive and observe conserved quantities in this open, balanced gain-loss system, both in the static and Floquet cases. Lastly, by measuring the circuit energy, we unveil a giant dynamical asymmetry along exceptional point (EP) contours that emerge symmetrically from the Hermitian degeneracies at Floquet resonances. Distinct from material or parametric gain and loss mechanisms, our protocol enables on-demand parity-time symmetry in a minimal classical system -- a single oscillator -- and may be ported to other realizations including metamaterials and optomechanical systems.