extreme quality mirrors (Reflection> 99.999%, optical absorption < 1ppm, flatness < 0.5 nm, scattering < 10 ppm)

a sophisticated distributed network of sensors to evaluate and subtract environmental background: electromagnetic perturbations, non-stationary ground deformations, sea waves, cloud passage, electromagnetic waves, cosmic rays, acoustic noise vibrations, anthropogenic movements

a sophisticated distributed and intelligent system of feedback controls and state of the art data analytics, machine and deep learning methods

state of the art laser injection system as well as a state-of-the-art detection and protection system, including sensors and baffles to control stray light, producing noise and, in the squeezed quantum state regime, de-coherence

super-attenuators damping seismic vibrations (<10-12 seismic reduction) of all the sensitive parts of the interferometer

ultra-high vacuum in the two 3 km tubes (P<10-9 Torr, the highest volume vacuum in Europe for Virgo and second in the world after the LIGO antenna’s having 4km tubes)

advanced quantum sensing techniques (frequency squeezing) taking the measurement errors below the quantum limit