Cavity QED Based on Strongly Localized Modes: Exponentially Enhancing Single-Atom Cooperativity

Large single-atom cooperativity in quantum systems is important for quantum information processing. Here, we propose to exponentially enhance the single-atom cooperativity parameter by exploiting the strongly localized effect of modes in cavity quantum electrodynamics (QED) systems. By increasing the wing width of a cavity with special geometry symmetry, the interference property allows us to exponentially improve the quality factor Q without altering the mode volume V for cavities supporting subwavelength light modes. This effectively overcomes the trade-off between Q and V in conventional subwavelength Fabry-P\'erot cavities. Consequently, we demonstrate the occurrence of ultralong vacuum Rabi oscillations and the generation of strong photon blockade by enhancing the single-atom cooperativity parameter. This Letter offers a promising approach for advancing coherent manipulation and holds significant potential for applications in establishing longer-distance quantum communication networks, enhancing the precision and stability of quantum sensors, and improving the efficiency of quantum algorithms.