Tight information bounds for spontaneous emission lifetime resolution of quantum sources with varied spectral purity

We generalize the theory of resolving a mixture of two closely spaced spontaneous emission lifetimes to include pure dephasing contributions to decoherence, leading to the resurgence of Rayleigh's Curse at small lifetime separations. Considerable resolution enhancement remains possible when lifetime broadening is more significant than that due to pure dephasing. In the limit that lifetime broadening dominates, one can achieve super-resolution either by a tailored one-photon measurement or Hong-Ou-Mandel interferometry. We describe conditions for which either choice is superior.