Observing and Evading Quantum Backaction in an Interferometer

The pursuit to eliminate classical noise sources in an interferometer has a long history Only recently have experimental conditions matured enough to enable measuring quantum backaction in the continuous displacement detection of a solid mechanical resonator Moreover reaching the regime in which mechanical vacuum fluctuations dominate opens the door to variety of experiments from ultra high position and force sensitivity to producing mechanical quantum states We use a macroscopic silicon nitride membrane