000231531 001__ 231531 000231531 005__ 20181203024832.0 000231531 0247_ $$2doi$$a10.1103/PhysRevX.7.031055 000231531 022__ $$a2160-3308 000231531 02470 $$2ISI$$a000411769600001 000231531 037__ $$aARTICLE 000231531 245__ $$aQuantum Correlations of Light from a Room-Temperature Mechanical Oscillator 000231531 260__ $$aCollege Pk$$bAmerican Physical Society$$c2017 000231531 269__ $$a2017 000231531 300__ $$a9 000231531 336__ $$aJournal Articles 000231531 520__ $$aWhen an optical field is reflected from a compliant mirror, its intensity and phase become quantum-correlated due to radiation pressure. These correlations form a valuable resource: the mirror may be viewed as an effective Kerr medium generating squeezed states of light, or the correlations may be used to erase backaction from an interferometric measurement of the mirror's position. To date, optomechanical quantum correlations have been observed in only a handful of cryogenic experiments, owing to the challenge of distilling them from thermomechanical noise. Accessing them at room temperature, however, would significantly extend their practical impact, with applications ranging from gravitational wave detection to chip-scale accelerometry. Here, we observe broadband quantum correlations developed in an optical field due to its interaction with a room-temperature nanomechanical oscillator, taking advantage of its high-cooperativity near-field coupling to an optical microcavity. The correlations manifest as a reduction in the fluctuations of a rotated quadrature of the field, in a frequency window spanning more than an octave below mechanical resonance. This is due to coherent cancellation of the two sources of quantum noise contaminating the measured quadrature-backaction and imprecision. Supplanting the backaction force with an off-resonant test force, we demonstrate the working principle behind a quantum-enhanced "variational" force measurement. 000231531 700__ $$0245939$$aSudhir, V.$$g201058 000231531 700__ $$0246969$$aSchilling, R.$$g222928 000231531 700__ $$0249431$$aFedorov, S. A.$$g260066 000231531 700__ $$aSchutz, H. 000231531 700__ $$0246503$$aWilson, D. J.$$g225172 000231531 700__ $$0244694$$aKippenberg, T. J.$$g182444 000231531 773__ $$j7$$k3$$q031055-1$$tPhysical Review X 000231531 909C0 $$0252348$$pLPQM 000231531 909CO $$ooai:infoscience.tind.io:231531$$particle$$pSB$$pSTI 000231531 917Z8 $$x268358 000231531 937__ $$aEPFL-ARTICLE-231531 000231531 973__ $$aEPFL$$rREVIEWED$$sPUBLISHED 000231531 980__ $$aARTICLE