Photonic integration technology is essential in achieving the goal of developing affordable and miniaturized quantum key distribution components. One of these components which is developed in the course of UNIQORN project is the “DPS Transmitter” chip.

In differential phase shift quantum key distribution, the information is encoded in the relative phase of two consequtive pulses, while the strength of the optical signal is reduced to have around 0.1 photon per each pulse. The protocol requires the generation of a coherent optical signal, together with operations such as pulse generation, phase encoding and optical attenuation. A monolithically integrated transmitter chip, which is shown in the microscope image above, is designed by the researchers from Photonic Integration group in Eindhoven University of Technology. The designed photonic chip incorporates the necessary optical components on an area of of 2mm x 4.6mm in order to generate and output the phase-encoded quantum signal.