Phd in PHYSICS

Thesis title: Photonics Technologies for Quantum Communication and Metrology

Entanglement is the quantum resource at the heart of most protocols of Quantum Information. It allows to outperform classical approaches, as in Quantum Metrology and Quantum Communication. Photonic implementation of quantum information studies represents a convenient choice: using single photons as quantum carrier has several advantages, such as easy mobility and manipulation. Here, integrated photonics represents one of the best technological platforms for the realization of quantum information protocols, allowing a better stability and scalability of quantum systems involving light. My thesis work investigated several scenarios by achieving experimental results in Quantum Metrology, Quantum Communication and Cryptography. In Quantum Communication framework, the entanglement distribution into different platforms was studied. A first work concerned the realization and characterization of an integrated tunable source of entangled pairs of photons at telecom wavelength. Another experiment, demonstrated the distribution of an hybrid entangled polarization-vector vortex beam state of photons at telecom wavelength, through an air-core fiber. Then, in a multipartite scenario, the entanglement was distributed and verified inside a quantum network between four different laboratories, in which five different nodes exploit four independent sources of entangled photon pairs. Finally, regarding Quantum Cryptography, the realization of a quantum key distribution (QKD) was realized. The adopted protocol is based on a modified version of the standard Ekert91 protocol. Notably, the QKD experiment was realized in a free-space urban channel between two parties 270 m apart. Then, we investigated the research area of Quantum Metrology. In this framework we studied the state of the art of Photonic Quantum Metrology and realized a review on this topic. In parallel a reconfigurable integrated multimode interferometer designed for the simultaneous estimation of two optical phases was experimentally realized and tested in quantum regime. Further, we tested the Neural Network performance in calibrating the same device. Then, the device was exploited to investigate optimized adaptive learning protocols for Quantum Metrology tasks. Another learning protocol, based on genetic evolution algorithm, was tested for the single phase estimation in a bulk two-mode Mach-Zehnder interferometer.