Single-Photon Transport In A Waveguide-QED Structure Containing Two Giant Atoms

Waveguide quantum electrodynamics(QED)system is an important platform to study the interaction between light and matter.In recent years,the structures consisting of a new type of giant atoms coupled to a waveguide have attracted extensive attentions,resulting in a new frontier of research,called quantum optics based on giant atom.The novelty of a giant atom system is that its multiple coupling points will produce interference effects and photon exchanges,resulting in many interesting phenomena,including the frequency-dependent decay rate and Lamb shift,decoherence-free interaction between two braided giant atoms,the non-exponential atomic dissipation,the oscillating bound states of photons,and so on.In particular,it’s important to study the scattering processes of a waveguide-QED system with giant atoms,which can deepen our understanding on the light-matter interactions,and help us to find new ways to manipulate single photons.In this paper,we focus on the single-photon transport properties in a one dimensional waveguide coupled with two giant atoms.Utilizing a real-space scattering method,we obtain the general analytical expressions of the single-photon scattering amplitudes,which are available for three basic topologies of the double-giant-atom systems.Then,based on these general expressions and by analyzing the master equation,we discuss the characteristics of the scattering spectrum,especially two important phenomena,asymmetric Fano lineshapes and EIT without control-field.On the one hand,we find the conditions of appearance of Fano lineshapes,and discuss the influences of the configurations of system and the phase delays between coupling points.On the other hand,we reveal two kinds of ways to achieve EIT-like spectra in double-giant-atom systems,which are based on multi-level systems consisting of atomic collective states and single-atom states,respectively.These phenomena may provide good guidance for manipulating photon transport and have potential applications in future quantum networks.