Strong photon antibunching and photon pair emission in a two-atom cavity QED system with van der Waals interaction

We investigate the generation of strong antibunching photons/photon pairs in a two-atom cavity QED system leveraging interatomic van der Waals (vdW) interaction. We show that the vdW interaction shifts the energy of double excited state, enabling the suppression of two-photon excitation via destructive interference in a diamond configuration. This leads to antibunching photon emission with extremely high purity. Furthermore, by tuning the vdW interaction strength, the conditions for conventional and unconventional photon blockades can be satisfied simultaneously, which significantly enhances the generation of single photon. Conversely, at the antiblockade excitation frequency, quantum Monte Carlo simulations demonstrate the feasibility of generating antibunching photon pairs with a high purity and reasonable leaking rate by selecting appropriate driving field Rabi frequency and vdW interaction strength. These findings on enhanced photon antibunching and photon pair emission may lead to more efficient and brighter quantum light sources, which is a key mechanism for optical quantum devices.