Photoswitchable quantum electrodynamics in a hybrid plasmonic quantum emitter

The design and preparation of quantum states free from environmental decohering effects is critically important for the development of on-chip quantum systems with robustness. One promising strategy is to harness quantum state superposition to construct decoherence-free subspace (DFS), which is termed dark state. Typically, the excitation of dark states relies on anti-phase-matching on two qubits and the inter-qubit distance is of wavelength scale, which limits the development of compact quantum chips. In the current work, a hybrid plasmonic quantum emitter was proposed, which was composed of strongly correlated quantum emitters intermediated by a plasmonic nanocavity. Through turning the plasmonic loss from drawback into advantage, the anti-phase-matching rule was broken by rapidly decaying the superposed bright state and preparing a sub-100 nm dark state with decay rate reduced by 3 orders of magnitudes. More interestingly, the dark state could be optically switched to a single-photon emitter with enhanced brightness through photon-blockade, with the quantum second order correlation function at zero delay showing a wide range of tunability down to 0.02.