Spatially-dependent nonreciprocal photon blockade via magnonic Kerr nonlinear effect and magnetic parametric amplification

We propose a theoretical scheme for realizing spatially-dependent nonreciprocal photon blockade (NPB) in a cavity magnonic system. The setup comprises a yttrium iron garnet sphere exhibiting a magnon Kerr nonlinearity and a cavity supporting a transverse Laguerre–Gaussian (LG) mode. The results indicate that, in the presence of magnetic parametric amplification, spatially-dependent NPB can be achieved by changing the direction-dependent magnonic Kerr effect. Essentially, the nonreciprocity originates from complete or incomplete quantum destructive interference between distinct two-photon excitation pathways, while the spatial modulation arises from the spatially-dependent coupling between the magnon mode and the LG cavity mode. More interestingly, through the analysis of NPB bidirectional comparison, we demonstrate that ideal NPB can be achieved at specific spatial positions. Subsequently, we further explored the effects of other system parameters, such as Kerr nonlinearity coefficient, dissipation rate, and environmental thermal noise, on the photon statistical properties at positions. The results indicate that the nonreciprocity between photon bunching and antibunching can be achieved under weaker Kerr nonlinearity conditions, and is robust to photon dissipation. It is also worth noting that our results are more easily observable under low temperature conditions. This work offers a new route toward high-dimensional single-photon sources and nonreciprocal quantum devices, with potential applications in high-capacity quantum communication.