Changing optical band structure with single photons

TL;DR

This paper proposes a theoretical method to alter the optical band structure using a single photon in a cold atom-nanophotonic system, enabling potential single-photon switching for quantum information applications.

Contribution

It introduces a novel mechanism where a single photon modifies the band structure via atom-photon interactions, leading to a single-photon switch in a nanophotonic system.

Findings

Single photon changes the atomic chain's effective periodicity.

System can switch from high transmission to high reflection.

Signatures observable through non-classical photon correlations.

Abstract

Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide (PCW), long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.