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 (QED) system. The mechanism relies on the multi-photon paths interference within the waveguide, which is clearly shown by the analytic parameter regime for $g^{(2)}(0)\approx0$. 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 $N$ ($N\ge2$), with a coherent state emerging for even numbers of cavities and a single-photon state for odd numbers. Our work 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.