Optical photons are excellent carriers of quantum information, but their lack of mutual interactions is a major roadblock for quantum technologies. We enable such interactions by transiently injecting the photons into an intra-cavity cold atomic gas and converting them into strongly interacting Rydberg polaritons. The Rydberg-blockaded cloud then acts as an effective two-level superatom with an enhanced coupling to light. We can coherently manipulate and efficiently detect its state, and use it to deterministically generate pulses of light with negative Wigner functions. This platform opens many perspectives for developing deterministic multi-photon gates, performing quantum measurements impossible with current techniques, generating non-classical optical resource states, and studying strongly correlated quantum fluids of light. We recently expanded this setup towards the multi-superatom regime. A possible M2 internship will consist in studying the effective interactions between optical pulses reflected from the cavity with two superatoms, leading to a PhD project focused on deterministic multi-photon quantum logic and Wigner-negative light states generation. Another internship topic will focus on the design and construction of a new setup with single atoms trapped next to a superatom. The following experimental PhD thesis will aim at developing quantum interconnects between static and flying qubits, in a collaboration with the quantum tech company Pasqal.