Fig. 1. Schematic of the dressed state energy levels of a single two-level atom-light field system

Fig. 2. Schematic of experimental setup for achieving photon blockade effect ^[9]

Fig. 3. Schematic of cavity EIT system ^[89]

Fig. 4. Photon statistics properties induced by cavity enhanced three-body interaction for single photon and single phonon blockade^[101]. (a) Single photon; (b) single phonon

Fig. 5. Vacuum Rabi mode splitting with a single photon^[109]. (a) Relationship between measured resonator transmission spectra and normalized external flux bias, and corresponding bias current applied to superconducting coil (top axis); (b) normalized resonator transmission; (c) resonator transmission approaching the degeneracy point; (d) vacuum Rabi mode splitting at degeneracy^point

Fig. 6. Localization of photonic crystal cavity modes relative to a single buried QD^[108]. (a) AFM topography of a photonic crystal nanocavity aligned to a hill of material on the surface arising from a QD buried below 63 nm; (b)electric field intensity of the photonic crystal cavity mode indicates the location of the buried QD; (c) photoluminescence spectrum before cavity fabrication of a single QD; (d) photoluminescence spectrum from the same QD after cavity fabrication ^[108]

Fig. 7. Schematic of experimental setup for on-chip nonclassical light generation ^[24]

Fig. 8. Schematic of strong photon blockade scheme^[36]. (a) Photon blockade scheme coupling a quantum dot with a nanocavity; (b) energy level diagram for a quantum dot coupled with the cavity field and the pump field; (c) energy level diagram of the dressed states in a coupled quantum dot-cavity system; (d) transition paths for the quantum interference model

Fig. 9. Unconventional photon blockade^[44]. (a) Conventional photon blockade by the anharmonicity of the JC ladder with suppression of two-photon component; (b) two excitation pathways (red and blue arrows) destructively interfere, in the unconventional photon blockade

Fig. 10. Experimental setup and results^[45]. (a) Microscope image of the two coupled Nb resonators used to observe the UPB; (b) evolution of the resonance frequency as a function of the superconducting quantum interference device (SQUID) flux; (c) evolution of |S12|2 as a function of frequency and SQUID flux; (d) microwave setup for measuring UPB

Fig. 11. Schematic of two-qubit cavity QED system with different cavity mode frequencies and qubit resonant frequencies^[123]

Fig. 12. Photon blockade combined with Stark frequency shift ^[46]. (a) Schematic of creation of photon blockade in a cavity with a single three-level atom; (b) typical anharmonic energy spectrum of the system; (c) relationship between vacuum Rabi splitting and optical Stark shift

Fig. 13. Nonreciprocal 1PB in a spinning Kerr resonator^[64]. (a) 1PB emerges by driving from its left side (ΔF>0); (b) PIT caused by two-photon resonance occurs by driving from the right side (ΔF<0)

Fig. 14. Experimental results^[135]. (a) Schematic of system; (b) ⁸⁷Rb atomic energy level structure

Fig. 15. Schematic of two PB mechanisms^[136]. (a) Hermitian mechanism; (b) NHPB mechanism

Fig. 16. Experimental setup for generating the two-photon blockade^[63]. (a) Schematic of single-atom cavity QED system; (b) energy level structure of strongly coupled cavity QED system; (c) energy level structure during cavity pumping; (d) energy level structure during atom driving; (e) vacuum Rabi splitting during cavity pumping and atom pumping

Fig. 17. Experimental setup and experimental scheme^[48]. (a) Schematic of the n-photon bunching emitter device; (b) a possible experimental scheme for placing quantum dots in micropillars^[48]

Fig. 18. Schematic of the two-photon JC model^[158]

Fig. 19. n-photon emission under atom-driven^[159]. (a) Intracavity photon number; (b) correlation functions; (c) distribution of g12τ (red-solid line) and g22τ (blue-dashed line) at the two-photon resonance; (d) distribution of g12τ (red-solid line) and g23τ (blue-dashed line) at the two-photon resonance

Fig. 20. Multimode transducer that enables conversion from single photons, two-photon bundles to super-Poissonian photon emission^[124]. Contour plots of (a) log[g120], (b) log[g130], and (c) n_s as functions of Δ_c and δ₂

Fig. 21. Single-photon, three-photon to four-photon bunching emission in a spin-3/2 JC model^[161]. Contour plots of (a) log[g140], (b) log[g150], and (c) n_s as functions of Δ_c and δ; (d) log[g1n0] and (e) n_s as a function of Δ_c; (f) distributions of g12τ (blue line) and g42τ (red line) at the four-photon resonance

Fig. 22. Schematic of energy level structures^[157]. (a) Schematic of model and Stokes resonance in the frequency domain; (b) ideal Raman process; energy level structures change in (c) strong coupling region and (d) strong driving (Mollow) region

Fig. 23. Statistic properties of motional two-phonon (left column) and three-phonon (right column) states^[62]. (a)(b) Distributions of g130 and g140 respectively, on the ω-δ parameter plane; (c) plots of g12τ (blue line) and g22τ (red-dashed line) at the red square in Fig. 23(a); (d) g12τ (blue line) and g32τ (red-dashed line) at the red square in Fig. 23(b)