Single photons by quenching the vacuum

TL;DR

This paper explores how to generate single photons from vacuum fluctuations by controlling a two-level system ultrastrongly coupled to a waveguide, resulting in non-Gaussian superpositions or individual photons depending on the system parameters.

Contribution

It demonstrates a method to engineer single-photon emission from vacuum fluctuations using a 2LS in the ultrastrong coupling regime, with detailed state characterization.

Findings

Vacuum fluctuations can be converted into single photons or non-Gaussian states.

The 2LS nonlinearity shapes the vacuum radiation into superpositions of cat states.

Photon emission can be approximated as individual photons when within band gaps.

Abstract

Heisenberg's uncertainty principle implies that the quantum vacuum is not empty but fluctuates. These fluctuations can be converted into radiation through nonadiabatic changes in the Hamiltonian. Here, we discuss how to control this vacuum radiation, engineering a single-photon emitter out of a two-level system (2LS) ultrastrongly coupled to a finite-band waveguide in a vacuum state. More precisely, we show the 2LS nonlinearity shapes the vacuum radiation into a nonGaussian superposition of even and odd cat states. When the 2LS bare frequency lays within the band gaps, this emission can be well approximated by individual photons. This picture is confirmed by a characterization of the ground and bound states, and a study of the dynamics with matrix product states and polaron Hamiltonian methods.