BROADBAND QUANTUM LIGHT: FROM SOURCE ENGINEERING TO QUANTUM METROLOGY

Abstract

The coming of quantum mechanics in the last century has represented one of the biggest revolutions of Physics and technology thereafter. The exploitation of quantum discoveries for the radical amelioration of currently technology provides one of the tantalising challenges of our time, in response to the Moore’s law that cannot escape from the bounds of the quantum reality itself. Citing the Quantum Manifesto: "previously untapped aspects of quantum theory are ready to be used as a resource in technologies with farreaching applications, including secure communication networks, sensitive sensors for biomedical imaging and fundamentally new paradigms of computation". Since light is increasely becoming a valuable carrier for modern communication, the upgrade to its quantum counterpart, quantum optics, seems to be in the same way one of the better proposal to implement in the future quantum technology. Going down this road in last decade many photon-based approaches have been attempted, with the deployment of single photons in order to transfer all the basic elements of quantum communication in the optical language. However, this new perspective of quantum technology needs also solid supports, assuring the efficiency and control of photonic devices, such as single-photon sources. In this thesis I examined the possibility of assessing frequency correlations occurring in a probabilistic two-photon generation event, the parametric down-conversion, through the use of quantum metrological approach. In order to well understand the current techniques for identification and measurement of spectral entanglement, a first exploration has been performed with pulse-shaping strategy through the use of spectral resolutive instruments. However, for nearly continuous wave pump light, things become quite more demanding, in terms of frequency resolution. Hence the needs of using quantum metrology schemes in order to find those methods aiming at circumvent such issue. After the comprehension of the opportunities provided by the multi parameter estimation approach on the characterisation of dispersive materials, a combination of metrological techniques, proofing that it constitutes a valuable tool in order to solve the spectral correlation assessment, even in future developments.