Description du sujet de thèse

Optomechanics explores the interaction between light and mechanical vibrations [1]. As a typical example, one can consider a Fabry-Perot cavity (i.e., optical mode), in which one of the two mirrors is vibrating (i.e., mechanical mode). These devices serve as invaluable platforms for studying macroscopic quantum phenomena such as macroscopic quantum coherence and classical-to-quantum transition. In particular, macroscopic quantum entanglement involving two massive oscillators has recently been observed in optomechanical platforms [2]. Practically, the applicability of modern quantum technologies in optomechanical networks ultimately requires quantum entanglement of light and many vibrations—i.e., multiple degenerate mechanical modes (i.e., same frequency) used as nodes of the network [3].

To display quantum properties, a mechanical mode must be cooled down close to its ground state (i.e., down to a few quanta of vibrational energy), which is typically achieved by leveraging the optical field. Sadly, when considering multiple degenerate modes, one cannot apply conventional cooling techniques that have been devised for single modes. There, the challenge originates from the emergence of dark modes (i.e., hybridization of degenerate modes), which are decouple from the optical field and cannot be cooled (thus precluding any quantumness) [4].

Throughout this PhD, the candidate will experimentally implement a new cooling technique intended to achieve the first-ever cooling of degenerate modes of a mechanical membrane. Compared to former strategies, here, a spatial light modulator is used to spatially shape the wavefront of the light beam. Such a modulation enables to exert simultaneously adapted optical forces on each mode in order to reduce (i.e., cool) their individual vibrations. The student will be closely guided by the advisor and will acquire both theoretical and experimental skills on optomechanics, quantum physics and spatial modulation techniques.

[1] Aspelmeyer et al., Rev Mod Phys, 2014
[2] Riedinger et al., Nature, 2018
[3] Kimble, Nature, 2008
[4] Lai et al., Phys Rev Letters, 2022

Contexte de travail

The PhD will take place in the team "Photonique et Matériaux" at LOMA (University of Bordeaux). The student will join the group of Nicolas Bachelard, whose activty focuses on quantum optomechanics.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.

Contraintes et risques

Use of class IV laser in the near infrared. Use of electric devices.