Cooperative Photon Emission from Indistinguishable Quantum Dots in Free Space

The ability to observe cooperative effects in light-matter coupling such as super-radiance is an important steppingstone towards realizing photon-mediated communication between matter qubits and a versatile quantum optics platform. Here, we experimentally demonstrate cooperative emission from a pair of individually tunable semiconductor quantum dots in a free-space (2D) geometry. By measuring photon correlations with Hanbury-Brown and Twiss and Hong-Ou-Mandel interferometers, we fully map the quantum optical signatures of super-radiant photon emission for resonant driving and incoherent pumping as a function of detuning. We find unambiguous evidence for collective emission, with particularly clear signatures of super-radiance from pulsed resonance fluorescence. This includes the observation of photon bunching and Poissonian photon statistics of the super-radiant state. Our data is well-described by a theoretical model which incorporates the sub-micron spacings between these emitters and the decoherence from the emitters’ solid-state environment. Our work represents an important step towards tailoring controllable cooperative behavior, enabling prospects for harnessing collective light-matter interaction effects.