Towards entanglement and interconversion of single mm-wave and optical photons in a hybrid cavity-QED system with Rydberg atoms

I will present our most recent progress towards entangling and interconverting single millimeter wave (mm-wave) and optical photons using Rydberg atoms as a transducer. Hybrid systems, which cross-couple optical and microwave regimes, can harness the unique strengths of optical systems for communication and microwave systems for quantum information processing, yielding a more powerful toolset for quantum information technology. The mm-wave band additionally offers access to single photon resolution at 1K, due to low thermal photon occupation at high frequencies. I will present our recent realization of a hybrid cavity with crossed mm-wave and optical modes, enabling smooth integration of cold atoms, laser beams and Rydberg excitations. The high-Q mm-wave cavity has a Q_tot = 3×10⁷ at 98GHz and mode volume of V =0.1λ³, which allows strong coupling with cooperativity of h=22000 between single mm-wave photon and a single Rydberg atom on the 36S → 35P transition. I will report our first observations of intra-cavity vacuum Rabi Splitting, Rydberg Electromagnetically Induced Transparency (EIT) and outline our path towards creating strong interactions between single mm-wave and optical photons.