基于局域耦合相位调控的巨原子单光子散射

Single-photon Scattering in Giant-atom Waveguide Systems with Modulated Coupling Phases

人造巨原子与波导多点耦合系统可打破传统量子光学偶极近似,诱导原子自干涉效应,近年来成为研究光子散射的重要物理平台。本文研究了该模型与一维波导多点手性耦合时,耦合点局域相位对单光子散射的影响。通过实空间哈密顿量方法精准解得系统的透射率与反射率表达式,传播相位被修正为依赖于入射光传播方向的手性相位,并通过设计手性相位来研究散射谱中手性引起的效应。研究发现当手性相位满足与耦合点个数无关的条件时,可使得兰姆能移消失,入射光子的透射谱能在共振处实现完美透射到完全反射的转变。此外,本文展现了引入原子内部自发辐射后,无需利用非马尔可夫延迟效应,仅调控手性相位即可实现完美的非互易光子散射。本文研究表明具有手性耦合点局域相位的巨原子-波导系统能为实现单光子路由提供颇具前景的候选平台。

Objective In quantum optics,(nature)atoms are orders of magnitude smaller than the wavelength of the light they interact with,which justifies the dipole approximation by allowing them to be viewed as point-like emitters.However,recent experiments extending the small(nature)atom platform to artificial'giant'atomic systems built from superconducting circuits,represent a breakdown of the dipole approximation and have attracted significant attention.The waveguide quantum electrodynamics systems with giant atoms have emerged as a new promising platform for engineering transport of photons and single-photon routing.The system enables strong tunable atom-waveguide coupling and manifests multiple-point self-interference in the photon scattering spectra.Recently,a setup with chiral interfaces between giant atoms and waveguides is no longer challenging based on technological progress,in particular,the chiral coupling can also allow decoherence-free states,nonreciprocal photon transport,and tunable Markovianity.Few studies have also considered the unequal local phases at different coupling points for photon routing.Nevertheless,here we study the single-photon scattering problem by considering chiral local coupling phases.Method We consider the system Hamiltonian in real-space and linear dispersion relation.We solve the Schrödinger equation within the single-photon manifold by considering theδ-function potential effect of the atom at the coupling point,where an appropriate ansatz is used for the probability amplitudes of the system's state,and the transmission and reflection coefficients are found with the direction-dependent propagating phases.The effects induced by chiral phases in the scattering spectra are studied by engineering the local coupling phases and coupling strengths.Results and Discussions We show that the transmission spectrum of an incident photon can transition from complete transmission to total reflection when the chiral phases satisfy specific conditions,regardless of the number of coupling points.In particular,the Lamb shifts vanishes at resonance,allowing for in situ control of the photon transport by varying the propagating phases.Moreover,when the internal atomic spontaneous emission is introduced,we show that perfect nonreciprocal photon scattering can be achieved by engineering the chiral local phases,in contrast to the non-Markovian retardation effect.Conclusion We have studied the effect of chiral local coupling phases on single-photon scattering.By engineering the chiral phases,it is not only possible to flexibly control the single-photon scattering properties,but also to achieve perfect nonreciprocal photon scattering.The findings of this study indicate that the giant-atom-waveguide system with chiral local coupling phases is a promising candidate for realizing single-photon routers and has potential applications in quantum network engineering and quantum information processing.