Massimo Giacomin

The successful application of Quantum Key Distribution is dependent on the accurate generation and detection of quantum states, and a communication mechanism that can withstand disturbances caused in the channel. The selection of the optimal encoding strategy is complex and is influenced by external elements such as the characteristics of the quantum channel. Polarization encoding is acknowledged for its dependability and low error rate, rendering it ideal for free-space links, whereas time-bin encoding is robust to birefringence, thereby making it suitable for optical fiber networks. The strength of polarization-based protocols is based on the full characterization of the receiver, to reconstruct the information encoded in the shared qubits. This is typically achieved through tomographic analysis, which adds to the complexity of the final protocol. In this research, we introduce a unique cross-encoded method, where high precision quantum states are produced using a self-regulating, calibration-free polarization modulator and then conveyed through a polarization-to-time-bin converter. A hybrid receiver is used to carry out both time-of-arrival and polarization measurements for decoding the quantum states. Moreover, the suggested receiver is optimized to perform a self-characterization process, utilizing the same photons in which the information is encoded. The adaptability of our approach can lead to a significant advancement in the creation of hybrid networks that incorporate both optical fiber and free-space networks.