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Authors
Abstract(s)
The goal of cryptography is to encode data in such a way that no one can decode it unless they are the
intended recipient. With the emergence of quantum computing, classical cryptography is not reliable
enough to protect sensitive information. Nevertheless, there are alternatives. Quantum Key Distribution
(QKD) is a method to secure communication based on the laws of quantum physics. Due to being
impossible to measure the quantum state of a system without disturbing it, QKD provides a way to
communicate between two parties while being, in theory, immune to eavesdropping.
In this work, a free-space high-speed QKD setup is proposed, with the objective of implementing
the polarization three-state one-decoy variant of the BB84 protocol. An assessment of the best type
of laser diode to use for free-space QKD is made between several options. The system’s performance
was assessed, incorporating a quantitative analysis of system losses and an estimation of the number
of photons traversing the quantum channel. The system achieved a Quantum Bit Error Rate (QBER)
of 1.58% for the Z basis and 1.46% for the X basis, for an average reception of two photons per pulse.
Preliminary QBER measurements were also undertaken in the context of Quantum Keyless Private
Communication protocols, focusing on the average number of photons per pulse.
Description
Keywords
Quantum Key Distribution Weak coherent pulses Quantum states measurements Secure optical communications.