Cavity nano-optomechanics in the single-photon strong-coupling regime – SinPhoCOM

The objectives of the project are to develop and explore a novel approach in cavity nano-optomechanics so as to reach the hitherto unexplored ultrastrong coupling regime, where a single intracavity photon can have a measurable impact on the oscillator and in turn on the cavity states. This regime, also called single-photon optomechanics, is a long lasting Grail in the field of cavity optomechanics, and has remained up to now far from experimental reach. This is due to the weak level of the optomechanical interaction of a single photon with macroscopic mechanical resonators, which was compensated by employing large photon numbers. However, in that situation, the intrinsic non-linearity of the optomechanical interaction gets diluted, while it represents an interesting resource for quantum optics and quantum communications by enabling the onset of non-linearities at the intracavity single photon level.

The regime of single photon cavity optomechanics can be achieved by combining ultrasensitive nanomechanical force sensors, with demonstrated sensitivities at the 10zN/Hz^(1/2) at 20mK, with optical microcavities which helps confining and enhancing the electromagnetic field.

The fundamental motivations for reaching this novel regime are multiple. First it will open the road towards novel applications in quantum optics and quantum information processing with photons, such as enabling quantum non-demolition readout of photon fluxes at extremely low light powers, measuring the single-photon recoil or providing a system for which non linearities are built up at the single intracavity photon level. Furthermore, there is also a large theoretical interest to explore those novel regimes, where mean fields and fluctuations in the intracavity photon number are of similar magnitudes, which remain largely unexplored up to now.

The nanoresonators employed are silicon carbide suspended nanowires, recently employed at Institut Néel as ultrasensitive vectorial force field sensors. Two types of optical microcavities will be used: fiber microcavities developed at Laboratoire Kastler Brossel in the Atomchips group, and photonic crystal cavities, developed at C2N. Both systems differ via their compacity and tunability, which permits to cover a broader span of applications while simultaneously allowing further optimization of those microstructures in novel regimes. Theoretical developments will be realized at LOMA. They will aim at exploring and formalizing this novel regime of cavity optomechanics, which allows to generate strong non-linearities at the single photon level, with fundamental applications in quantum optics and quantum measurement theory.