Squeezed light from a silicon micromechanical resonator

Quantum fluctuations of a laser are transferred onto the motion of a mechanical resonator and interfere with the fluctuations of the light reflected from the resonator, leading to ‘squeezed’ light with optical noise suppressed below the standard quantum limit. Squeezed-light chips in prospect Light falling on a mechanical object exerts a small force that alters the object's motion — an effect that is studied in the field of optomechanics. The motion of the object itself exerts back-action on the light, resulting in 'squeezed' light with non-classical behaviour. Squeezed light with quantum fluctuations below that of the vacuum field was proposed nearly three decades ago as a means of beating the standard quantum limits in precision force measurements. Safavi-Naeini et al . demonstrate squeezed-light generation using continuous position measurement of a solid-state optomechanical system fabricated from a silicon microchip and composed of a micromechanical resonator coupled to a nanophotonic cavity. With further device improvements, on-chip squeezing at significant levels should be possible, making such integrated microscale devices ideal for precision metrology applications. Monitoring a mechanical object’s motion, even with the gentle touch of light, fundamentally alters its dynamics. The experimental manifestation of this basic principle of quantum mechanics, its link to the quantum nature of light and the extension of quantum measurement to the macroscopic realm have all received extensive attention over the past half-century 1 , 2 . The use of squeezed light, with quantum fluctuations below that of the vacuum field, was proposed nearly three decades ago 3 as a means of reducing the optical read-out noise in precision force measurements. Conversely, it has also been proposed that a continuous measurement of a mirror’s position with light may itself give rise to squeezed light 4 , 5 . Such squeezed-light generation has recently been demonstrated in a system of ultracold gas-phase atoms 6 whose centre-of-mass motion is analogous to the motion of a mirror. Here we describe the continuous position measurement of a solid-state, optomechanical system fabricated from a silicon microchip and comprising a micromechanical resonator coupled to a nanophotonic cavity. Laser light sent into the cavity is used to measure the fluctuations in the position of the mechanical resonator at a measurement rate comparable to its resonance frequency and greater than its thermal d