Fig. 8From: Prospects and applications of on-chip lasersSilicon-based integrated quantum photonic applications. a The first field tests for a metropolitan QKD connected by optical fiber.Adapted with permission from [152]. copyright 2018, APS. b Daylight free-space QKD using silicon photonic circuits. Adapted with permission from [153], copyright 2021, NPG. c A programmable qudit-based quantum processor in silicon-based IQP circuits. Adapted with permission from [154], copyright 2022, NPG. d A quantum photonic simulator and diamond nitrogen-vacancy center. Adapted with permission from [155] copyright 2017, NPGBack to article page