Аннотация:Interferometric detection of gravitational waves at levels of astrophysical interest is expected to require measurement of optical phase differences of $\ensuremath{\le}{10}^{\ensuremath{-}10}$ rad. To achieve this sensitivity the measurement must be made at the quantum (shot noise) limit. We have built a laboratory-scale interferometer to investigate limits to sensing the phase at this level, and obtained, with 70 W of circulating power, a phase sensitivity limited by shot noise of $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}10}\phantom{\rule{0ex}{0ex}}\mathrm{rad}/\sqrt{\mathrm{Hz}}$ at frequencies above 1.5 kHz. We describe the experiment and discuss the implications for the Laser Interferometer Gravitational-Wave Observatory (LIGO).
