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The future envisaged global-scale quantum communication network will comprise various nodes interconnected via optical fibers or free-space channels, depending on the link distance. The free-space segment of such a network should guarantee certain key requirements, such as daytime operation and the compatibility with the complementary telecom-based fiber infrastructure. In addition, space-to-ground links will require the capability of designing light and compact quantum devices to be placed in orbit. For these reasons, investigating available solutions matching all the above requirements is still necessary. Here we present a full prototype for daylight quantum key distribution at 1550 nm exploiting an integrated silicon-photonics chip as state encoder. We tested our prototype in the urban area of Padua (Italy) over a 145m-long free-space link, obtaining a quantum bit error rate around 0.5% and an averaged secret key rate of 30 kbps during a whole sunny day (from 11:00 to 20:00). The developed chip represents a cost-effective solution for portable free-space transmitters and a promising resource to design quantum optical payloads for future satellite missions.
Measurement-device-independent quantum key distribution (MDI-QKD) removes all detector side channels and enables secure QKD with an untrusted relay. It is suitable for building a star-type quantum access network, where the complicated and expensive m
We designed and demonstrated experimentally a silicon photonics integrated dynamic polarization controller which is a crucial component of a continuous-variable quantum key distribution system. By using a variable step simulated annealing approach, w
The incorporation of multiplexing techniques used in Microwave Photonics to Quantum Key Distribution (QKD) systems bring important advantages enabling the simultaneous and parallel delivery of multiple keys between a central station and different end
We present a silicon optical transmitter for polarization-encoded quantum key distribution (QKD). The chip was fabricated in a standard silicon photonic foundry process and integrated a pulse generator, intensity modulator, variable optical attenuato
Many quantum key distribution (QKD) implementations using a free space transmission path are restricted to operation at night time in order to distinguish the signal photons used for a secure key establishment from background light. Here, we present