Quantum Optomechanics

A large part of our research efforts involves the use of radiation-pressure coupling to control the state of microscopic and nanoscopic mechanical systems through the powerful tool embodied by light. The implications of this mechanism for our quest on quantum control at the mesoscopic level are very interesting!

The typical configuration of an optomechanical cavity: a Fabry-Perot resonator with a movable end-mirror, driven by a strong external pump.

In 2006, three seminal experiments have demonstrated the potential for radiation-pressure coupling implemented in a set-up consisting of an optical cavity with a vibrating end-mirror to cool mechanical micro/nano-structures all the way down to their quantum mechanical ground state. This will imply the possibility to observe the discreteness of the spectrum of a massive mechanical oscillator and, thus, the observation of genuine quantum mechanical effects. Ground-state cooling of mechanical motion has been demonstrated experimentally in at least three diverse settings:

Since then, the occurrence of non-classical phenomena, such as the emergence of opto-mechanical entanglement, the squeezing of the state of a mechanical oscillator, the engineering of strategies for the enforcement of quantum features in massive vibrating structures, have been predicted. Cavity quantum optomechanics is now one of the most exciting and fervent areas of modern quantum physics and embodies a viable route towards mesoscopic quantumness and the exploration of the quantum-to-classical transition. QTeQ has given a great contribution to both the experimental and theoretical efforts in this field. Besides being part of the first seminal experiment proving passive cooling of a mechanical structure by radiation pressure coupling, we have worked intensively on five different directions:

1. Revelation of optomechanical entanglement and non-classical features: we are looking for non-disruptive, experimentally friendly ways to infer the non-classical properties of a massive mechanical device. Our strategies include the use of light, coherent atomic samples, and single-atom probes.
2. Hybridization of quantum optomechanics: we are studying the interplay between mechanical structures, light, and ultracold atomic gases for the sake of building quantum interfaces and achieving genuine mesoscopic quantum mechanical features.
3. Enforcing non-classicality: we are working on quantum optics schemes for the enforcement of quantum mechanical properties in the state of massive mechanical systems. We have proposed and all-optical way to achieve and certify non-classicality in a single-mode mechanical device and a protocol to “activate” optomechanical entanglement.
4. New effects in cavity optomechanics (interference and cooperativity): we study new interferometric designs for cavity quantum optomechanics able to exploit quantum interference in order to enhance the possibilities inherent in the radiation-pressure coupling. Our approach uses scattering as a resource to understand and enhance optomechanics and its features for non-linear optics.
5. Optomechanical networking: we believe that extended networks for quantum communication can be made out of optomechanical nodes connected by optical fields. We have investigated the feasibility of entanglement distribution among such nodes and its retrieval.