Fig. 1. （a） Diagrammatic sketch of Gaussian imaging system; (b) Airy spot formed with different number of photons, N is the photon number

Fig. 2. （a） Experimental setup of first-photon imaging; （b） Experimental results of first-photon imaging: The first column is the point cloud recorded by the avalanche photodiode, the second column is the reflectivity estimated from the time-of-flight of the first photon, the third column is the computational image via regularization method, the fourth column is the 3-dimentianl image estimated from the different views^[12]

Fig. 3. Diagrammatic sketch of the principle of correlated imaging

Fig. 4. Unfolded picture of the ghost imaging system with psudothermal light

Fig. 5. （a） Experimental setup of ghost imaging with entanglement source; (b) Results of ghost imaging with entanglement source^[54]

Fig. 6. （a） Experimental setup of heralded ghost imaging ; (b) Comparison between the results from heralded ghost imaging and that via direct imaging^[14]

Fig. 7. （a） Experimental setup of quantum imaging with entanglement source; (b) Comparison between the results from quantum imaging with entanglement source and that via direct imaging^[58]

Fig. 8. （a） Principle of ghost imaging with coherent detection and pulse compression; (b)Simulation results of ghost imaging with coherent detection and pulse compression^[46]

Fig. 9. Simulation results of the three ghost imaging LiDAR under different detection signal-to-noise ratio^[47]

Fig. 10. （a） Diagrammatic sketch of ghost imaging at 1.3 km; (b) Comparison between the experimental results of the temporal correlation method and that from traditional method; (c) Imaging results of objects at different distance from the temporal correlation method^[49]

Fig. 11. (a) Statistical distribution of photon pulses detected by bucket detector in single photon ghost imaging; (b) Results of ghost imaging single photon^[50]

Fig. 12. （a） Diagrammatic sketch of single photon ghost imaging；（b）Results of single photon polarization ghost imaging^[51]

Fig. 13. (a) Diagrammatic sketch of first-photon imaging; (b) Experimental results of fast first-photon ghost imaging^[52]

Fig. 14. Experimental setup and results of fast first-photon ghost imaging for 3-dimentional object at 100 km distance^[53]

Fig. 15. （a） Experimental setup of zero-photon imaging; (b) Photon statistical and the experimental results of zero-photon imaging^[73]