Observation of topologically protected bound states in a one dimensional photonic system

TL;DR

This paper demonstrates the experimental observation of topologically protected bound states in a one-dimensional photonic system, revealing new phenomena and advancing control over topological phases in quantum systems.

Contribution

It provides the first direct imaging of topologically protected localized states in photonic quantum walks and uncovers a novel topological bound state unique to periodically driven systems.

Findings

Confirmed topologically protected localized states in photonic systems

Discovered a new topological bound state in periodically driven systems

Showed control of topological properties via periodic driving

Abstract

One of the most striking features of quantum mechanics is the appearance of phases of matter with topological origins. These phases result in remarkably robust macroscopic phenomena such as the edge modes in integer quantum Hall systems, the gapless surface states of topological insulators, and elementary excitations with non-abelian statistics in fractional quantum Hall systems and topological superconductors. Many of these states hold promise in the applications to quantum memories and quantum computation. Artificial quantum systems, with their precise controllability, provide a versatile platform for creating and probing a wide variety of topological phases. Here we investigate topological phenomena in one dimension, using photonic quantum walks. The photon evolution simulates the dynamics of topological phases which have been predicted to arise in, for example, polyacetylene. We experimentally confirm the long-standing prediction of topologically protected localized states associated with these phases by directly imaging their wavefunctions. Moreover, we reveal an entirely new topological phenomenon: the existence of a topologically protected pair of bound states which is unique to periodically driven systems. Our experiment demonstrates a powerful new approach for controlling topological properties of quantum systems through periodic driving.