STAGE Cavity-enhanced quantum engineering of light with cold Rydberg atoms

We recently built a new platform for quantum engineering of light, capable to create efficient
interactions between optical photons, tunable in range, strength and dimensionality. To induce
these interactions, we transiently convert the photons into Rydberg polaritons inside a cold gas of
Rb atoms trapped inside a “twisted optical resonator with a controllable geometry. By controlling
the resonator’s and the cloud’s parameters, we can manipulate photons propagating in free space
or confined inside the resonator, and control the dimension and the shape of the space they
explore.
This platform can be used to test the limits of fundamental no-go theorems in quantum logic,
perform quantum measurements impossible with current techniques, and generate non-classical
multi-mode states of free-propagating light. Moreover, it gives us access to a regime where
intracavity photons form a strongly correlated quantum fluid, making this setup is ideally suited for
real-time, single-particle-resolved investigations of topological effects appearing in condensedmatter
systems. Currently, we are benchmarking its performance as a single-photon source.
The M2 internship will aim at gaining control over the collective internal state of the atomic cloud
and use it as a single “super-atom with an enhanced coupling to the cavity. The following steps
will be to produce non-classical “Schrödinger’s cat states of free-propagating light in a
deterministic way. We will then investigate the possibility to implement a deterministic twophoton
logic gate using this platform, before moving towards a multi-photon, multi-mode regime
of strongly correlated quantum photonic fluids. The project is mainly experimental, with a strong
theoretical component.