Single-photon sources are key components for solid-state-based quantum photonics. This research project has two primary goals in this context and is carried out in close collaboration with Ding’s RG. The first focus is on the fundamental understanding and reduction of quasi-classical noise in two technologically important types of quantum dots: (a) near-surface, passivated GaAs QDs, which promise superior coupling to hybrid quantum photonic structures and show – with suitable passivation – surprisingly good emission properties according to pre-experiments, and (b) novel semiconductor QDs in the range of telecommunication wavelengths, which promise very high quantum yield even at 1.55 μm. Both systems are subject to specific charge and spin noise, which will be identified, inter alia, by a combination of (quantum) spin noise spectroscopy and resonance fluorescence. This will help reduce the relevant noise sources and develop optimised single-photon sources, which are fabricated in Ding’s RG.
The second focus of the project is on the quantum mechanical noise of very high-quality GaAs QDs, which are coupled by photonic cavities and waveguides. This intrinsic quantum noise arises, in the simplest case, e.g. due to coherent population dynamics, and in the more general case due to the coupling of quasi-identical QDs. The noise will be studied first by ‘standard’ spin noise spectroscopy and, in the more general case, by correlated spin noise spectroscopy on the single-photon level in combination with resonance fluorescence. One aim of these measurements is not only to optimise the control of the noise, but also to deduce effective coupling strengths in photonic integrated circuits from quantum mechanical noise.
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