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Quantum Optomechanics with a levitating nanoparticle

Periodic Reporting for period 3 - QnanoMECA (Quantum Optomechanics with a levitating nanoparticle)

Reporting period: 2018-10-01 to 2020-05-31

Micro- and nano-mechanical oscillators with high quality (Q)-factors have gained great interest for their capability to sense very small forces. Recently, this interest has exponentially grown owing to their potential to push the current limits of experimental quantum physics and contribute to our further understanding of quantum effects with large objects. Despite recent advances in the design and fabrication of mechanical resonators, their Q-factor 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 performances required for some of the envisioned applications. A very attractive alternative to conventional mechanical resonators is based on optically levitated nano-objects in vacuum. In particular, a nanoparticle trapped in the focus of a laser beam in vacuum is mechanically disconnected from its environment and hence does not suffer from clamping losses. First experiments on this configuration have confirmed the unique capability of this approach and demonstrated the largest mechanical Q-factor ever observed at room temperature. The QnanoMECA project aims at capitalizing on the unique capability of optically levitating nanoparticles to advance the field of optomechanics well beyond the current state-of-the-art. The project is primarily aimed at bringing us closer to ground-state cooling at room temperature. We also explore new paradigms of optomechanics based on the latest advances of nano-optics. The unique optomechanical properties of the developed systems based on levitated nanoparticles will be used to explore new physical regimes whose experimental observation has been so far hindered by current experimental limitations.
The work performed so far can be summarized as follows:

- Towards ground state cooling at room temperature – A first main part of our work was the implementation of a novel cooling experiment involving the coupling of a levitated nanoparticle to a high-finesse optical macrocavity. While this novel platform has already enabled us to observed efficient resolved sideband cooling, we are currently optimizing the set-up to achieve unprecedented cooling performance and get us closer to mechanical ground-state at room temperature.

- Novel optomechanical configurations based on near field optical cavities – Another major part of our work has focused on the coupling of a levitated nanoparticle to a near field optical nanocavity. We have so far focused our efforts on designing and fabricating the optical nanocavity as well as developing a suitable loading procedure to control the nanoparticle/nanocacvity interaction.

- Optomechanics with single quantum emitters – Last but not least, the final main part of our work so far has dealt with extending levitation optomechanics to nano-objects having internal energy levels. To this aim, we have developed a novel experiment combining electrostatic (Paul) and optical trapping. As a proof of principle, we have already demonstrated trapping of individual nanodiamonds hosting a single NV center.
On the one hand, the QnanoMECA is foreseen to push the limits of experimental physics, by enabling us to enter so far unexplored physical regimes. On the other hand, it will also advance our understanding of fundamental physics and answer questions that remain without answers. Beyond this generation of knowledge, the project will train young scientist, both at the pre-doc and postdoc levels, who are the next generation of European scientific leaders.