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Quantum Optomechanics with a levitating nanoparticle

Periodic Reporting for period 4 - QnanoMECA (Quantum Optomechanics with a levitating nanoparticle)

Reporting period: 2020-06-01 to 2020-09-30

Nano-mechanical resonators have gained great interest owing to their potential to push the current limits of experimental quantum physics and contribute to our further understanding of quantum effects with objects of increasing complexity. Despite recent advances in the design and fabrication of mechanical resonators, their performance has so far been limited by coupling to the environment through physical contact to a support. This limitation is foreseen to become a bottleneck in the field which might hinder reaching the targeted physical regimes. A very attractive alternative to conventional mechanical resonators is based on levitated nano-objects in vacuum. In particular, a nanoparticle trapped in the focus of a laser beam in vacuum is mechanically isolated from its environment and hence does not suffer from clamping losses. Original experiments have confirmed the unique capabilities of this configuration and demonstrated the sharpest mechanical resonances ever observed at room temperature. QnanoMECA capitalized on the unique capability of levitated nanoparticles to advance the field of optomechanics well beyond the current state-of-the-art. The project primarily aimed at bringing the particle in the quantum regime where its motion is reduced to its fundamental limit. The second main objective was to explore new regimes of optomechanics based on the latest advances of nano-optics. Finally, we aimed at extending levitation to more complex nanoparticles whose intrinsic properties could allow further control of the optomechanical properties.
The first main part of our work focused on achieving an extreme isolation of the levitated nanoparticle to a level where its motion is governed by quantum mechanics. This was achieved by coupling an optically trapped particle to a very stable optical cavity formed by two facing mirrors. Under specific conditions, the cavity has the ability to convert mechanical energy into light and hence reduce the particle motion. This approach enabled us to stabilize the nanoparticle to its fundamental limit, known as the mechanical quantum regime.
A second aspect of our work related to exploring how the concept of levitation optomechanics could benefit from a more efficient interaction of the levitated particle with light, enabled by the latest advances in nano-optics. Through nano-structuring of optical materials nano-optics enables to concentrate light well-beyond what is allowed by conventional optics using lenses and mirrors. By exploiting the enhanced light matter-interaction resulting from the coupling of the levitated particle to a nano-optical cavity, we were able to reach unprecedented optomechanical regimes foreseen to benefit, for instance, the development of ultra-sensitive inertial sensors.
Last but not least, the third part of our work focused on extending levitation optomechanics to nanoparticles hosting quantum emitters. The properties of the latter indeed offer, through the use of a specific light, further control over the particle motion. To this aim, we successfully developed a novel hybrid levitation platform, combining optical and electric forces, which paves the way to the future generation of optomechanical experiments.
QnanoMECA has been overall very successful by meeting all original objectives. The scientific outcome has led to more than ten publications in prestigious scientific journals (three additional manuscripts have been already submitted and two other ones are in preparation) and multiple invited talks in international conferences.
On the one hand, QnanoMECA advanced the field of optomechanics by developing new levitation schemes that address the limitations of prior configurations and enable a further control over the levitated object dynamics. On the other hand, our work also contributed to gain fundamental understanding of levitated optomechanical systems and allowed accessing new physical regimes that were not accessible so far.