Optical backaction-evading measurement of a mechanical oscillator

Abstract

Quantum mechanics imposes a limit on the precision of a continuous position measurement of a harmonic oscillator, due to backaction arising from quantum fluctuations in the measurement field. This standard quantum limit can be surpassed by monitoring only one of the two non-commuting quadratures of the motion, known as backaction-evading measurement. This technique has not been implemented using optical interferometers to date. Here we demonstrate, in a cavity optomechanical system operating in the optical domain, a continuous two-tone backaction-evading measurement of a localized gigahertz-frequency mechanical mode of a photonic-crystal nanobeam cryogenically and optomechanically cooled close to the ground state. Employing quantum-limited optical heterodyne detection, we explicitly show the transition from conventional to backaction-evading measurement. We observe up to 0.67 dB (14%) reduction of total measurement noise, thereby demonstrating the viability of backaction-evading measurements in nanomechanical resonators for optical ultrasensitive measurements of motion and force.

Laser Cooling of a Nanomechanical Oscillator to Its Zero-Point Energy

“…Laser cooling of mechanical systems occurs via coupling of mechanical and electromagnetic degrees of freedom (optomechanical coupling) and has been demonstrated with a wide range of structures [12,[16][17][18][19][20][21][22][23][24][25]. It has led to the observation of radiation pressure shot noise [26], ponderomotive squeezing of light [27,28], and motional sideband asymmetry [16,[29][30][31][32].Many optomechanical protocols, including mechanical squeezing [33][34][35][36], entanglement [37], state swaps [38], generation of non-classical states [39][40][41][42], and back-action evading (BAE) measurements below the standard quantum limit (SQL) [43][44][45], require ground state preparation of a wellsideband-resolved system, where Stokes and anti-Stokes motional transitions can be driven selectively. In this case, driving of anti-Stokes transitions can be efficiently applied to damp the motion and sideband cool the system.…”

An optomechanical heat engine with feedback-controlled in-loop light

“…The results that we have presented correspond to systems in the resolved sideband regime and in cryogenic environments (considering a 1 MHz resonator the results in figures 3, 5, 6 and 12 would correspond to an external temperature of 100 mK, the results of figures 7-10, instead, would correspond to 1.7 K). Many experimental setups, both in the optical or microwave regimes, can be employed for demonstrating our proposal as for example [22][23][24][25][26][27]. In order to test the efficiency of this device one should be able to measure the energy variations and to distinguish the contributions due to heat and work.…”

Estimation of squeezing in a nonlinear quadrature of a mechanical oscillator

“…Other more demanding options would include, for example, swapping the mechanical state to optics with subsequent optical tomography, or detection of the mechanical characteristic function via coupling to an atom (see [78] and references therein). The QND interaction has been implemented in the domains of electromechanics [17,79,80] and optomechanics [81].…”