Realizing quantum optics in structured environments with giant atoms

To go beyond quantum optics in free-space setups, atom-light interfaces with structured photonic environments are often employed to realize unconventional quantum electrodynamics (QED) phenomena. However, when employed as quantum buses, those long-distance nanostructures are limited by fabrication disorders. In this work, we alternatively propose to realize structured lightmatter interactions by engineering multiple coupling points of hybrid giant atom-conventionalenvironments without any periodic structure. We present a generic optimization method to obtain the real-space coupling sequence for multiple coupling points. We report a broadband chiral emission in a very wide frequency regime, with no analog in other quantum setups. Moreover, we show that the QED phenomena in the band gap environment, such as fractional atomic decay and dipole-dipole interactions mediated by a bound state, can be observed in our setup. Numerical results indicate that our proposal is robust against fabrication disorders of the coupling sequence. Our work opens up a new route for realizing unconventional light-matter interactions.