Control of non-classical light states by linear and non-linear interaction in hybrid systems of single semiconductor quantum dots and alkali atomic vapor

• Applicants: Dr. Robert Löw; Professor Dr. Peter Michler
• Subject Area: Experimental Condensed Matter Physics
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 281308554

The central aim of the proposed research project is the realization and detailed investigation of new hybrid concepts and schemes which provide control to generate and/or manipulate non-classical states of light by distinct interaction between photons emitted from single semiconductor-quantum dots (QDs) and alkali atomic vapor as the control medium. The fundamental basis for all planned investigations is the generation of spectrally narrow-band resonance fluorescence (RF) from individual single Indium-Gallium-Arsenide (InGaAs)-QDs as a source of photons which can be brought to controlled interaction with the optical resonances of atomic cesium (133Cs) at ~894 nm (D1 hyperfine structure quadruplet). One important prerequisite for sophisticated QD-atom interaction experiments will be a precise tuning capability of RF with respect to the fixed atomic reference frequencies of the D1 hyperfine structure. The efficiency of (non-)linear interactions will critically depend on the mutual spectral similarity between the photon source and the spectral response characteristics of the thermal atomic gas, dominated by Doppler broadening, which acts as the control medium. Therefore, another very important aspect will be to gain flexible control on the RF emission linewidth in order to adjust its bandwidth to the atomic transitions. In this project, we plan to utilize different conditioning techniques, i.e. (a) deterministic pi-pulsed optical QD excitation, (b) direct generation of ultra-narrowband sub-Poissonian RF by coherent, elastic photon scattering on a single QD in the weak excitation regime (Heitler regime), and (c) spectral post-filtering of single-QD RF from the regimes of pi-pulsed and also cw-dressed emission above saturation. This can be achieved by using a specially designed high-finesse Fabry-Pérot interferometer, or alternatively, for the first time in combination with QD-RF, the technique of FADOF-type (Faraday anomalous dispersion optical filter) transmission filtering. Using such conditioned photons, the anticipated goals of the project focus on fundamental applications in the field of optical quantum information processing. One of our aimed applications will be controlled single-photon storage and delay by generation of slow light within the strongly dispersive frequency regime between selected Cs-D1 resonances and storage via an off-resonant Raman-scheme. The second major goal of the project focuses at the manipulation of stored photons and the generation of higher-order photon number (Fock) states by using cesium atomic vapor in combination of highly excited Rydberg gas medium with controllably attractive or repulsive atom-atom interaction. A Rydberg gas can act e.g., as an optical transistor for two individual photons to merge into a common mode channel. The effect of photon-photon scattering can be controlled externally by an appropriate Rydberg pump laser for the atomic medium.

• DFG Programme: Research Grants