Missions

Optical levitation is an emerging theme in optomechanics where a nanoparticle is trapped in vacuum using a laser focused through a high numerical aperture objective. The laser produces an optical force equivalent to a mechanical spring, and the system can be regarded as a mass-spring resonator oscillating at kHz frequencies. Due to the quality of their resonances, levitated systems are currently being exploited for high-sensitivity metrology, detecting gravitational waves, or searching for dark matter. Above all, levitation offers the remarkable prospect of exalting quantum properties at the mesoscopic scale (i.e., at the quantum-classical transition) to confirm (or rule out) fundamental hypotheses of quantum physics.

To reach the quantum regime, the nanoparticle must be cooled close to its fundamental vibrational state (i.e., to a few quanta of vibrational energy). In other words, the amplitude of its oscillations, which are driven by collisions with residual air molecules in the vacuum chamber, must be reduced. This cooling can be achieved using optical methods by monitoring the nanoparticle's motion and temporally modulating the laser to exert a force constantly opposed to the object's displacements. However, due to the relative weakness of the optical forces involved, such methods have not yet succeeded in reaching the fundamental quantum state of a levitated nanoparticle.

Throughout this thesis, the candidate will experimentally implement a new optical levitation architecture to achieve the first optical cooling of a nanoparticle to its fundamental quantum state. This new architecture will also be used to prepare the nanoparticle in non-classical (i.e., quantum) vibrational states. The student will be closely supervised and will acquire theoretical and experimental skills in optomechanics, optical levitation, quantum mechanics, and quantum optics.

Activités

The candidate will focus on developing an experimental optical levitation platform to cool a nanoparticle to its fundamental quantum state. Additionally, the setup will be used to implement temporal protocols for preparing non-classical states. During this primarily experimental thesis, the candidate may need to perform theoretical developments in quantum optomechanics and numerical simulations based on the encountered needs.

Compétences

The candidate should have basic practical experience in optics (Fourier optics, geometric optics, etc.) and electronics and be able to handle lasers and simple optoelectronic systems. Theoretical knowledge in quantum optics and optomechanics is not required but would be an asset.

Contexte de travail

The candidate will join Nicolas Bachelard's team, composed of 3 PhD students working on related themes. He or she will benefit from daily interactions with the supervisor and regular meetings to best guide the thesis progress. All necessary materials for implementing the experimental setup have already been procured.

Contraintes et risques

Use of Class 4 infrared lasers.