Phase-controlled single-photon router and chiral scattering in a <i>π</i>-shaped waveguide with giant atoms

Abstract We investigate a π -shaped single-photon router composed of an infinite waveguide and two semi-infinite waveguides coupled through double two-level giant atoms, where each giant atom is further coupled to a single-mode cavity. Using the real-space approach, analytical expressions of the single-photon scattering amplitudes are derived. The numerical results show that optimal routing with unit efficiency can be achieved by precisely adjusting frequency detunings between the incident photon and the atomic as well as cavity resonances, the accumulated phase, local coupling phases and coupling strengths between atoms, waveguides and cavities. Additionally, chiral single-photon scattering is observed, demonstrating a strong direction-dependence in the scattering properties, with perfect chiral scattering achieved under specific phase-matching conditions. We believe that our research has considerable potential applications for designing advanced optical quantum devices and implementing efficient single-photon quantum routing based on giant atom architectures.