High Purcell\nEnhancement in Quantum-Dot Hybrid Circular\nBragg Grating Cavities for GHz Clock Rate Generation of Indistinguishable\nPhotons

We present Purcell-enhanced (<i>F</i><sub>P</sub> > 25)\nsemiconductor InAs quantum dot decay times of <i>T</i><sub>1</sub> < 30 ps, enabled by deterministic hybrid circular Bragg\ngratings (hCBGs). We investigate the benefits of these short <i>T</i><sub>1</sub>-times on the two-photon indistinguishability\nfor quasi-resonant and strictly resonant excitation and observe visibilities\nof ≥96% at 12.5 ns time delay of consecutively emitted photons.\nThe strongly Purcell-enhanced decay times enable a high degree of\nindistinguishability for elevated temperatures of up to 30 K and,\nmoreover, allow for excitation of up to 1.28 GHz repetition rate.\nOur work highlights the prospects of highly Purcell-enhanced solid-state\nquantum emitters for applications in quantum information and technologies\noperating at GHz clock rates.