Electronically programmable polaritonic molecule for on demand quantum memory

Spectral hole burning in a spectrally disordered ensemble of coherent emitters coupled to a cavity leads to the observation of a resonance feature within the spectral hole. This feature is narrower than the bare cavity resonance and stems from the reduced group velocity in the hole. We show rigorously through an effective Fano-Feshbach projection that the observed feature is a polaritonic resonator mode in a low-energy subspace. We create a ''polaritonic molecule " by burning two spectrally disparate holes in an ensemble of erbium ions doped in lithium niobate micro ring resonator and couple the two modes electronically with an RF field, resulting in oscillation of the slow light field between the two modes. By tailoring the relative widths of the spectral holes, we create an asymmetric molecule that can store and release a photon on demand.