In August 2017 Virgo made its first gravitational-wave detections together with LIGO. The detection of the gravitational-waves emitted by the binary black-hole coalescence (GW170814) and the binary neutron star coalescence (GW170817, with its electromagnetic counterparts GRB170817a and AT2017gfo) had dramatic consequences for astrophysics, cosmology and tests of general relativity. In order to increase the volume of the observed sky and the signal-to-noise ratio of the signals detected, then fully to exploit the scientific potential of the gravitational-wave detector network, an increase of the Virgo sensitivity is crucial. In the next years, periods of data takings alternated with periods of detector’s upgrades will be performed. The goal of this thesis is to twofold: 1) Using advanced data-analysis and data processing techniques, the candidate will contribute to the improvement of the quality of the Virgo data and identification of the noise sources, 2) The candidate will contribute to the experimental activitiy carried out on the Virgo site in order to reduce the detector's noise, understand the optical properties of the interferometer and implement the technique of the squeezed states of light. 

The candidate will be based at APC laboratory, within the Virgo-APC group. Visits on the Virgo site will be made on a regular basis.