Development of high performance systems for quantum communications

Quantum mechanics has proven to be one of the most successful theories of the 20th century, enabling revolutionary applications across multiple fields. Among these, quantum communication stands out for its ability to exploit the laws of quantum mechanics to achieve levels of security impossible with classical systems. In a world increasingly reliant on the secure transmission of information, Quantum Key Distribution (QKD) offers unconditional security based on fundamental physical principles rather than computational assumptions. Despite remarkable progress, the realization of practical, large-scale QKD networks still faces major technological challenges, including high-speed state preparation, precise synchronization, and long-term stability. This thesis presents the design and implementation of high-performance hardware systems for quantum communication, both for discrete-variable (DV) and continuous-variable (CV) systems. The work combines FPGA-based digital logic, optoelectronic control, and quantum optics to enable fast, stable, and reconfigurable experimental platforms. These technologies are applied to the realization of polarization- and time-bin-encoded sources for QKD, achieving gigahertz operation rates for the first and supporting high-dimensional quantum states for the second, with excellent phase stability for both. The same hardware framework is extended to digital signal processing for CV-QKD, demonstrating also the coexistence of DV and CV schemes within the same optical channel. This thesis aims to highlight recent developments in the pursuit of higher performance and scalability of quantum communication systems, paving the way for the realization of practical, large-scale QKD networks.