The Formation of Photon-Molecules in Nanoscale Waveguides

TL;DR

This paper explores how photons can form bound states, called photon-molecules, within nanoscale waveguides due to vibrational interactions, with implications for quantum information processing.

Contribution

It introduces a formalism using Green's functions and T-matrix approximation to analyze photon-molecule formation and identifies conditions for their emergence in nanowires.

Findings

Photon-molecules form at a critical temperature.

Photon bound states exhibit significant quantum nonlinear phase.

Photon-molecules can function as quantum logic gates.

Abstract

We investigate the formation of photon bound states in a system of interacting photons inside nanoscale wires. The photons interact through the exchange of vibrational modes induced along the waveguide mainly due to radiation pressure. The problem of many-body photons is treated in using the formalism of contour Green's functions under the T-matrix approximation. The complex pole of the T-matrix is a signature for the appearance of photon-molecules. The analysis of such singularity provides the critical temperature at which the T-matrix approximation breaks down and photon-molecules appear. For strongly interacting slow photons the amplitude of the photon-molecule wavefunction acquires a significant quantum nonlinear phase inside the nanowire. Photon bound-states can be implemented for quantum information processing as quantum logic gates, e.g. for $\pi$ phase shift the photon-molecule is shown to serve as a Z-controlled gate.