Location: LOMA, Bordeaux University, France

Type: Experimental

Supervisor(s): Nicolas Bachelard (LOMA, Bordeaux University)

Email(s): nicolas.bachelard@u-bordeaux.fr

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Optical levitation is an emerging theme in optomechanics where a nanoparticle is trapped in a vacuum using a laser focused by high numerical aperture optics. The laser produces an optical force equivalent to a mechanical spring, and the system can be considered 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 perspective 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.

During 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. The applicant has to possess a citizenship from the EU or an affiliated country, such as the UK, Switzerland or Norway.