We propose a scheme for generating high-purity fluorescence two-photon bundles from two spatially separate two-level emitters, whose correlated excitation is mediated by a strongly driven auxiliary emitter. Unlike bosonic-mode-based approaches, the finite excitation space of the two target emitters intrinsically excludes higher-excitation manifolds, and thus eliminates impurity photons associated with undesired higher-excitation states. We further analytically characterize the residual population of off-resonant single-excitation states and show that suppressing the corresponding leakage improves photon bundle purity. Our scheme offers a feasible pathway for constructing high-purity quantum light sources with promising applications in quantum information processing.
N-photon bundles constitute a class of highly nonclassical quantum states of light. They are a specific type of photon emission, where light quanta are released from a cavity only in groups of
N particles with a characteristic photon number statistics that may be taken as their fingerprint. We consider two solid-state cavity quantum electrodynamics (cQED) systems in terms of their suitability as emitters of
N-photon bundles. As one example, we consider a semiconductor quantum-dot--microcavity system coupled to longitudinal acoustic phonons. There, we find the environmental influence to be detrimental to the emission of
N-photon bundles. The other example is a superconducting qubit inside a microwave resonator. In these systems, pure dephasing is not important and an experimentally feasible parameter regime is found, where bundle emission can be observed.