Use of a RF-SQUID in a quantum non demolition scheme

The sensitivity required for detecting gravitational waves seems higher than the limit imposed to a linear detector by quantum mechanics. To overcome this drawback, many groups are developing quantum non demolition (QND) schemes. Here we present a QND scheme based on the use of an RF-SQUID. The SQUID is used as a non linear element in order to obtain a combination of a three frequencies inverting and non inverting up-converter.