Single-Photon Scattering Properties Based On Giant Atoms Interacting With 1D Waveguides

As an extension of cavity quantum electrodynamics(QED)system,waveguide QED system which explores the interaction between waveguide and matter has received extensive attention.Compared with the localized mode,the photons in the waveguide can be easily guided to the distant subsystem.Therefore,waveguide QED is widely used in quantum networks.In recent years,with the continuous development and great progress of artificial atom and superconducting quantum circuit experiments,the waveguide QED experiment has made rapid progress.It has been used not only to explore the interaction between small atoms and photons in waveguides,but also to study the interaction between giant atoms and photons in waveguides.Here,the difference between a small atom and a giant atom is whether the size is much smaller than the wavelength of light,or comparable to the appearance of light waves.Compared with the small atom,the giant atom has multiple pins effectively coupled with the waveguide,which enables the photon in the waveguide and the giant atom to generate quantum interference for many times,making the system of interaction between the giant atom and the waveguide more controllable.In view of this,this paper intends to explore the scattering characteristics of single photon in waveguide based on this system,and provide certain theoretical basis for the development and design of efficient single photon quantum devices.In this paper,we mainly study the single photon scattering phenomena in two giant atomwaveguide systems.The first is a cascade coupling system of two two-level giant atoms with one-dimensional waveguides.The coupling strength of the two-level giant atoms with onedimensional waveguides has phase difference in spatial arrangement.We study the properties of single photon transport in the quantum optical system and find that multiple quantum interference occurs during the transport of single photon in the system.Due to the spatial asymmetry of the coupling pins of two-level giant atoms,the photon transmission in the waveguide is non-reciprocal.The principle design of single photon quantum diode can be realized.The second is the nested coupling system of single-pin two-level atom and three-pin two-level giant atom with waveguide.The single-pin two-level giant atom and three-pin two-level giant atom are arranged regularly in the waveguide.In this system,the coupling point of the single-pin two-level giant atom and the waveguide is coincident with the coupling point of the three-pin two-level giant atom and there is interaction between the single-pin two-level giant atom and the three-pin two-level giant atom.We find that due to the interaction between two two-level giant atoms,the two-level atomic energy levels are reconstructed to form a cascade three-level structure.The single photon in the three-level system is similar to the driving light.When the energy of the light is equal to the energy of the two-level atom transition,the Fano resonance and e IT-like phenomena will appear when the spacing of the atomic pin is adjusted.The transmission peak of EIT can be adjusted by the number of atoms.Our research has some significance for realizing the design of frequency comb and quantum optical switch.