Johannes Schall, Marielle Deconinck, Nikolai Bart, Matthias Florian, Martin von Helversen, Christian Dangel, Ronny Schmidt, Lucas Bremer, Frederik Bopp, Isabell Hüllen, Christopher Gies, Dirk Reuter, Andreas D. Wieck, Sven Rodt, Jonathan J. Finley, Frank Jahnke, Arne Ludwig, Stephan Reitzenstein

Adv. Quantum Technol. 4, 2100002 (2021)

Self-organized semiconductor quantum dots represent almost ideal two-levelsystems, which have strong potential to applications in photonic quantumtechnologies. For instance, they can act as emitters in close-to-ideal quantumlight sources. Coupled quantum dot systems with significantly increasedfunctionality are potentially of even stronger interest since they can be used tohost ultra-stable singlet-triplet spin qubits for efficient spin-photon interfacesand for deterministic photonic 2D cluster-state generation. An advancedquantum dot molecule (QDM) device is realized and excellent opticalproperties are demonstrated. The device includes electrically controllableQDMs based on stacked quantum dots in a pin-diode structure. The QDMsare deterministically integrated into a photonic structure with a circular Bragggrating using in situ electron beam lithography. A photon extraction efficiencyof up to (24±4)% is measured in good agreement with numericalsimulations. The coupling character of the QDMs is clearly demonstrated bybias voltage dependent spectroscopy that also controls the orbital couplingsof the QDMs and their charge state in quantitative agreement with theory.The QDM devices show excellent single-photon emission properties with amulti-photon suppression ofg(2)(0)=(3.9±0.5)×10−3. These metrics makethe developed QDM devices attractive building blocks for use in futurephotonic quantum networks using advanced nanophotonic hardware.