We envision future information society enabled by superconducting logic working in core networks to switch and rout data streams in optical communications network. Until now, the efficient utilisation of superconducting rapid single flux quantum (RSFQ)-logic has been impeded by the difficulty in making the electrical interconnection from the RSFQ-chip to the external world because the RSFQ-chips operate in cryostats at 4 K temperature.

We propose a fiber optic connection to the RFSQ in order to tap into its potential and allow more than 100 times lower power consumption per logic operation than state-of-the-art electronics today. Moreover, RSFQ-circuits are very fast (200–300 GHz clock frequency), enabling low latencies in networking. In the LIGHTNING project we demonstrate for the first time high-efficiency 100 GHz, 1.55 μm photodiodes (PD) and their integration to single mode optical fibers, working at 4 K temperature and an electrical link from the PD to the RSFQ-chip.