Tunable single-photon frequency converter in a waveguide with a giant V-type atom

TL;DR

This paper investigates a tunable single-photon frequency converter using a giant V-type atom in a waveguide, demonstrating how nonreciprocity and quantum interference can enhance conversion efficiency.

Contribution

It introduces a model for single-photon frequency conversion with a giant V-type atom, analyzing nonreciprocal effects and the role of quantum self-interference in tuning conversion probabilities.

Findings

Conversion probability can reach unity with nonreciprocity.

Inelastic scattering spectra differ between Markovian and non-Markovian regimes.

Quantum self-interference controls the frequency conversion efficiency.

Abstract

We study the single-photon scattering in a one-dimensional (1D) waveguide coupled to one transition of a $V$-type giant atom (GA), whose other transition is coherently driven by an classical field. The inelastic scattering of single photons by the GA realizes the single-photon frequency conversion. By applying the Lippmann-Schwinger equation, the scattering coefficients for single photons incident from different directions are obtained, which present different scattering spectra in the Markovian and the non-Markovian regimes. The conversion contrast characterizing the nonreciprocity is also analyzed in both regimes. It is found that the probability of the frequency up- or down-conversion vanishes as long as the emission from either transition pathways for single photons is suppressed, but it is enhanced and even reach unity by introducing the nonreciprocity. It is the quantum self-interference induced by the scale of this two-legged GA and the phase difference between the GA-waveguide couplings that tune the probability of the frequency up- or down-conversion.