Non-classical light generated by quantum-noise-driven cavity optomechanics

Abstract

Optomechanical systems, in which light drives and is affected by the motion of a massive object, will comprise a new framework for nonlinear quantum optics, with applications ranging from the storage and transduction of quantum information to enhanced detection sensitivity in gravitational wave detectors. However, quantum optical effects in optomechanical systems have remained obscure, because their detection requires the object’s motion to be dominated by vacuum fluctuations in the optical radiation pressure; so far, direct observations have been stymied by technical and thermal noise. Here we report an implementation of cavity optomechanics using ultracold atoms in which the collective atomic motion is dominantly driven by quantum fluctuations in radiation pressure. The back-action of this motion onto the cavity light field produces ponderomotive squeezing. We detect this quantum phenomenon by measuring sub-shot-noise optical squeezing. Furthermore, the system acts as a low-power, high-gain, nonlinear parametric amplifier for optical fluctuations, demonstrating a gain of 20 dB with a pump corresponding to an average of only seven intracavity photons. These findings may pave the way for low-power quantum optical devices, surpassing quantum limits on position and force sensing, and the control and measurement of motion in quantum gases.

Cavity-mediated coupling of mechanical oscillators limited by quantum back-action

“…We observe the quantum back-action noise imparted by the optical coupling resulting in correlated mechanical fluctuations of the two oscillators. Our results illustrate challenges and opportunities of coupling quantum objects with light for applications of quantum cavity optomechanics [8][9][10][11][12][13][14] .Cavity optomechanical systems comprised of a single mechanical oscillator interacting with a single electromagnetic cavity mode 15 serve useful quantum-mechanical functions, such as generating squeezed light [16][17][18] , detecting forces with quantum-limited sensitivity 19 or through back-action-evading measurement 20 , and both entangling and amplifying mechanical and optical modes 21 . Systems containing several mechanical elements offer additional capabilities.…”

“…Cavity optomechanical systems comprised of a single mechanical oscillator interacting with a single electromagnetic cavity mode 15 serve useful quantum-mechanical functions, such as generating squeezed light [16][17][18] , detecting forces with quantum-limited sensitivity 19 or through back-action-evading measurement 20 , and both entangling and amplifying mechanical and optical modes 21 . Systems containing several mechanical elements offer additional capabilities.…”

Cascaded optical transparency in multimode-cavity optomechanical systems

“…For example, quantum memories have been proposed based on EIT 8,9 , where the optical transmission and delay directly determine the information transfer efficiency and storage time 10,11 . EIT has also been demonstrated with cavity optomechanical systems 6,7 , which has advanced into the quantum regime, and paved the way to realize integrated quantum devices [12][13][14][15][16] . In spite of great advances in the performance of optomechanical devices, it remains challenging to realize EIT with both high optical transmission and long optical delay.…”

Quantum Limits on Measurement and Control of a Mechanical Oscillator

“…Figure 4.4 shows the resulting homodyne photocurrent spectrum, showing optical squeezing at the level of ≈ 1.5%, arising from imprecision-back-action correlations in the homodyne detector. Squeezing due to the radiation pressure interaction, recently been observed in other experiments [302,324,325], is a canonical indicator of both the intrinsic quantum correlations present in the meter field, and the quantum-limited detection capability of the experiment.…”

“…Back-action arises from vacuum fluctuations of the amplitude quadrature, which are imprinted onto the phase via the back-action-driven motion of the oscillator. In a homodyne detector, these quantum correlations manifest as ponderomotive squeezing of an appropriately chosen field quadrature [294,302,303]. In a heterodyne detector, they manifest as motional sideband asymmetry [304][305][306][307].…”