Controlled Single-Photon Emission

Marlan O. Scully

Recent work has shown that collective single photon emission from an ensemble of resonate two-level atoms, i.e., single photon superradiance, is a rich field of study. The present Letter addresses the flip side of superradiance, i.e., subradiance. Single photon subradiant states are potentially stable against collective spontaneous emission and can have ultrafast readout. In particular it is shown how many atom collective effects provide a new way to control spontaneous emission by preparing and switching between subradiant and superradiant states.

Shengwang Du

Björn Jonas, Dirk Heinze, Eva Schöll +8 more

Tailored nanoscale quantum light sources, matching the specific needs of use cases, are crucial building blocks for photonic quantum technologies. Several different approaches to realize solid-state quantum emitters with high performance have been pursued and different concepts for energy tuning have been established. However, the properties of the emitted photons are always defined by the individual quantum emitter and can therefore not be controlled with full flexibility. Here we introduce an all-optical nonlinear method to tailor and control the single photon emission. We demonstrate a laser-controlled down-conversion process from an excited state of a semiconductor quantum three-level system. Based on this concept, we realize energy tuning and polarization control of the single photon emission with a control-laser field. Our results mark an important step towards tailored single photon emission from a photonic quantum system based on quantum optical principles.

Sang Kyu Kim, Eduardo Zubizarreta Casalengua, Katarina Boos +9 more

In the single-photon emission from a two-level system, multiphotons are generally regarded as accidental, undesired, and unrelated to the mechanism. In coherently driven systems, however, they form the cornerstone of single-photon emission, which arises from quantum interferences between virtual multiphoton fluctuations of the emitter and the Poissonian superposition of all number states induced by the driving. Here, we demonstrate how one can control the multiphoton dynamics by disrupting these quantum interferences through an external homodyne control of the emitter's mean field. Experimentally, we observed a transition from single-photon to multiphoton emission, up to three-photon correlations. We show that, counterintuitively, quantum fluctuations always play a major qualitative role, even and, in fact, especially when their quantitative contribution is vanishing. Our findings provide distinct insights into the paradoxical character of quantum mechanics and open pathways for mean-field engineering as a tool for precision multiphoton control.

Matthew T. Rakher