Single-photon blockade in quasichiral atom–photon interaction: simultaneous high purity and high efficiency

We investigate the single-photon blockade (1PB) in quasichiral regime of atom-photon interaction that mediates via dissipative environment, where effective is asymmetrical but achiral. The synthetic magnetic current closed-loop coupling breaks down reciprocity interaction, resulting an and even completely unidirectional between two selected quantum states. As example, we couple single-atom cavity-QED (cQED) system to a strongly auxiliary cavity. find regime, unconventional photon (UPB) always incorporates with conventional (CPB) condition maximum chirality. Furthermore, show 1PB combines advantages UPB CPB, demonstrating perfect purity, higher efficiency, smooth time dynamics as well lower requirement modes achieve UPB. Our work paves way for towards practical applications reveals intriguing quantum-optics phenomena light-matter interaction.