Efficient single-photon directional transfer between waveguides via two giant atoms.

We investigate the single-photon transport properties in a double-waveguide quantum electrodynamic system. We force the energy degeneracy of the collective states by adjusting the direct coupling strength between the two giant atoms. Our results indicate that resonant photons can be completely transferred between the two waveguides owing to the scattering interference of eigenstates, which also results in the directional propagation of resonant photons in the output waveguide.