Chiral Interaction Induced Near-Perfect Photon Blockade

Based on the scattering matrix method, we theoretically demonstrate that the chiral interaction can induce the almost perfect photon blockade (PB) in the waveguide-cavity quantum electrodynamics system. The mechanism relies on the multiphoton path's interference within the waveguide, which is clearly shown by the analytic parameter regime for g^{(2)}(0)≈0. When N cavities are introduced into the system, there are N optimal parameter points accordingly for the almost perfect PB, where the required lowest chirality decreases exponentially with increasing N, and these optimal points are robust against disorder in the system's frequencies. Under resonant driving and fixed chirality conditions, the output light depends solely on the parity of N (N≥2), with a coherent state emerging for even numbers of cavities and a single-photon state for odd numbers. Our Letter offers an alternative route for achieving almost perfect PB effects with high single-photon transmission by employing the chirality of system, with potential application in the on-chip single-photon source with integrability.