An interferometric gravitational wave detector as a quantum-gravity apparatus

As a consequence of the extreme precision of the measurements it performs, a LIGO/VIRGO-type interferometric gravitational wave detector (IGWD) is a macroscopic apparatus for which quantum effects are not negligible. We observe that this property of IGWDs can be exploited to probe some aspects of the interface between Quantum Mechanics and Gravity. In particular, we find that IGWDs can test two recent proposals concerning the interplay between “system” and apparatus in Quantum Gravity regimes. We also show that there is an absolute limitation on the measurability of the amplitude of a gravitational wave. This measurability bound is obtained by combining a well-known “standard quantum limit,” which depends on the mass of the mirrors used by the IGWDs, and a limitation on the mass of the mirrors that is imposed by gravitational effects.