Highest redshift quasars and the early growth of supermassive black holes in the universe

The discovery of luminous quasars at z > 6 indicates the existence of billion-solar-mass black holes at the end of cosmic dark ages. They provide the best probes of the early growth of supermassive black holes in the universe, the relation between the formation of early galaxies and black holes, and put constraints on the role of quasars and AGNs to the cosmic reionization. About 1000 quasars have been discovered at z > 4, including 50 at z > 5 and eight at z > 6. In this proceeding, I review the recent observational results on surveys and detailed follow-up observations of the highest redshift quasars, including the evolution of luminosity function, the evolution of spectral properties and chemical enrichment history, distribution of black hole masses and the host galaxy properties.