Quantum Key Distribution Exploiting a Faraday Rotator and a Single Spad

Nowadays encryption is exploited for protecting information exchange in several applications. Nevertheless the security of commonly used algorithms of encryption is based on the extremely high computational cost required for message decryption. On the other hand, quantum key distribution (QKD) allows for exchanging a key between two users (Alice and Bob) in a way that has been proved as unconditional secure, thanks to the fundamental principles of quantum physics [1–3]. However to make the QKD a reliable and effective widespread solution, it is essential to reduce the cost and expand the scalability.