Photonics technologies for quantum communication and metrology

Entanglement is the quantum resource at the heart of most protocols of quantum Information, allowing to outperform classical approaches of its application, such as quantum metrology and quantum communication. Photonic implementation of quantum information studies represents a convenient choice: using single photons as quantum carriers 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. A first work concerned the realization and characterization of an integrated tunable source of entangled pairs of photons with telecom wavelength. As a second step 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 has been experimentally realized. Further, the device has been exploited to investigate optimized adaptive learning protocols for quantum metrology tasks. Another learning protocol, based on genetic evolution algorithm, has been tested for the single phase estimation in a 2-modes Mach-Zehnder interferometer. In quantum communication framework, the entanglement distribution in two different platforms has been studied. A first experiment, demonstrated the distribution of an hybrid entangled polarization-vector vortex beam state of photons in telecom wavelength, through an air-core fiber. Then, in a multiparties scenario, the entanglement was distributed and verified inside a quantum network between four different laboratories, in which five different nodes exploit fours independent sources of entangled photon pairs. Finally, regarding quantum cryptography, the realization of a free-space quantum key distribution (QKD) has just been made. This QKD experiment is based on a modified version of the standard Ekert91 protocol, between two parties 270m apart.