Interferometric gravitational wave detectors: state of the art and fundamental noise issues

Interferometric gravitational wave detectors, such as Virgo in Italy, LIGO in the US and GE0600 in Germany, have already completed scientific data runs. 2nd generation detectors, such as Advanced Virgo and Advanced LIGO will start operation within the next 5 years and preliminary design studies have already begun for 3rd generation detectors. It is hoped that we will soon be able to reach the holy grail of the first direct detection of gravitational radiation and start the exciting field of gravitational wave astronomy. The LIGO Scientific Collaboration (LSC) and the Virgo collaboration have published many observational results of great scientific relevance. For the future, the main challenge is to further increase the detector sensitivity by reducing the instrumental noise, in particular quantum noise, i.e. a fundamental noise term intrinsic to the measurement process itself. This can be achieved by the implementation of forefront quantum optics techniques.