Tunable photon blockade with a single atom in a cavity under electromagnetically induced transparency

We present an experimental proposal to achieve a strong photon blockade by employing electromagnetically induced transparency (EIT) with single alkaline-earth-metal atom trapped in optical cavity. In the presence of Stark shift, both second-order correlation function and cavity transmission exhibit asymmetric structures between red blue sidebands For weak control field, quantum statistics for coherent window (i.e. atomic quasi-dark state resonance) are insensitive which should also be immune spontaneous emission excited taking advantage intrinsic dark-state polariton EIT. Interestingly, exploiting interplay shift at resonance has optimal $g^{(2)}(0)\sim10^{-4}$ high simultaneously. The underlying physical mechanism is ascribed enhanced spectrum anharmonicity EIT hosted nonlinearity loss-insensitive resonance, essentially different from conventional emerging Kerr cavity-EIT. Our results reveal new strategy realize high-quality sources, could open up avenue engineering nonclassical states electrodynamics.