Applicazione della luce quantistica alla rivelazione del rumore ologra?co

One of the main challenges in physics today is to merge quantum theory and the theory of general relativity into a unified framework, the so-called quantum gravity. Several attempts in this sense have been considered, but only in the past few years the possibility of testing experimentally predictions of these models has become real. More specifically, effects connected to the hypothesis of non commutativity of positions variables in different directions have been considered in a system of two coupled Michelson interferometer, the so-called ¿holometer". This idea led to the planning of a double 40 m high-sensitive interferometer at Fermilab. In the first part of this study the essential aspects of the Fermilab experiment are reviewed, explaining how they can be used to experimentally demonstrate the non commutativity of positions variables through the detection of an additional phase noise, the so-called ¿holographic" noise. The fluctuations induced by holographic noise in a single interferometer are expected to be extremely faint, completely hidden by the shot-noise. However in two interferometers close each other, the fluctuation are expected to be correlated and thus more easily identified by statistical rejection of uncorrelated noise. However, the ultimate limit for holometer sensitivity, as for any classical-light based apparatus, is dictated by the shot-noise. This noise has its origin in the quantum nature of light and is proportional to sqrtN, where N is the average number of photons implied. It can accordingly be reduced using more power in the system, but since for technical reason power can not be increased arbitrarily the possibility of going beyond the shot-noise limit by exploiting quantum optical states is of the greatest interest. This thesis, after an introduction to some of the main topics in quantum optics, presents how quantum states of light could lead to significant improvements in the holometer sensitivity. In particular, consequences of the injection of squeezed light and twin-beam state are analyzed, and respective advantages underlined. This result has two interesting aspects: on the one hand it shows that quantum, and in particular correlated states of light can lead to great advantages in interferometric measurements and this paves the way for future metrology applications. On the other hand it prompts the possibility of testing quantum gravity in experimental configurations affordable in a traditional quantum optics laboratory with current technology. The last part of this study deal with the experimental implementation, in INRiM laboratories, of a holometer injected with quantum light. The final goal is to demonstrate that the injection of squeezed light in the normally unused ports reduces the noise below the shot-noise limit, achieving unprecedented sensitivity in detecting phase fluctuation. It would be the first time that quantum light is used to enhance the performance of a system of this kind. The work we did during my stage at the INRiM is described in detail. We first prepared and characterized two classical 1 m Michelson interferometers in power recycling configuration, then we projected and implemented proper systems to control their degrees of freedom. Preliminary measurements of visibility, calibration, divergence of the lasers are also reported. The aim of the future work will be to compare the sensitivities achieved in the different configurations, thus demonstrating the quantum improvements