Quantum-optical spectroscopy of a two-level system using an electrically driven micropillar laser as a resonant excitation source

Two-level emitters are the main building blocks of photonic quantum technologies and are model systems for the exploration of quantum optics in the solid state. Most interesting is the strict resonant excitation of such emitters to control their occupation coherently and to generate close to ideal quantum light, which is of utmost importance for applications in photonic quantum technology. To date, the approaches and experiments in this field have been performed exclusively using bulky lasers, which hinders the application of resonantly driven two-level emitters in compact photonic quantum systems. Here we address this issue and present a concept for a compact resonantly driven single-photon source by performing quantum-optical spectroscopy of a two-level system using a compact high- β microlaser as the excitation source. The two-level system is based on a semiconductor quantum dot (QD), which is excited resonantly by a fiber-coupled electrically driven micropillar laser. We dress the excitonic state of the QD under continuous wave excitation, and trigger the emission of single photons with strong multi-photon suppression ( g ( 2 ) ( 0 ) = 0.02 ) and high photon indistinguishability ( V = 57±9%) via pulsed resonant excitation at 156 MHz. These results clearly demonstrate the high potential of our resonant excitation scheme, which can pave the way for compact electrically driven quantum light sources with excellent quantum properties to enable the implementation of advanced quantum communication protocols. Microlasers: tiny pillars yield practically perfect quantum light Sending encrypted quantum data over long distances is set to become more feasible using a low-cost system for generating photons one at a time. Repeating signals in a quantum network requires techniques for emitting single photons that preserve information such as polarization states. Stephan Reitzenstein from the Technische Universität Berlin, Germany, and co-workers report that bulky lasers used in typical quantum repeaters can be downsized using low-dimensional semiconductor nanostructures known as quantum dots. They fabricated micropillar structures, each containing aluminum–gallium–arsenic-based quantum dots as active medium, which produce coherent laser pulses when electrically stimulated. By directing the micropillar-driven pulses onto another quantum dot that resonates after absorbing laser light, the team triggered emission of high-quality, individual photons that may be beneficia