Chirped Multi-photon adiabatic passage for a four-level ladder-type Rydberg excitation

We develop a multi-photon adiabatic passage to realize a highly efficient Rydberg excitation in a four-level ladder-type atomic system. The adiabatic passage is based on the existence of a novel quasi-dark state in the cascade excitation system where the frequencies of the lasers are appropriately chirped with time. We also investigate the influence of the interatomic Rydberg interaction on the passage and extend its application to the preparation of anti-blockade Rydberg atom pairs in the Rydberg blockade regime.