(color online) Integrated photonic devices for QKD. (a) Alice’s module is integrated on InP, (b) Bob’s module is integrated on SiO_xN_y chip. (c) and (f) The waveguide cross-section based on InP and SiO_xN_y platform, respectively. (d) Wavelength tunable laser made of two tunable distributed Bragg reflectors (T-DBR) and a semiconductor optical amplifier (SOA). (e) Electro-optic phase modulators (EOPM). (g) Microscopic image of the receiver’s delay lines. Reproduced from Ref. [137].