Heterogenous quantum systems for single photon delay and pulse shaping (HQSys)

• Applicants: Professor Dr. Stephan Reitzenstein; Professor Dr. Janik Wolters
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 448532670

Photonic quantum technology is an exciting field in science and technology. Potential applications include secure quantum communication, quantum computing and on the long-term the Quantum Internet. These have in common that information is encoded in single photons acting as flying qubits. Importantly, these flying qubits need to be efficiently interfaced with stationary qubits to implement quantum memories and quantum gates. The overarching goal of this project is to develop and test a quantum memory for the storage and retrieval as well as for the efficient spectral/temporal waveform manipulation of single quantum dot photons. Our project realizes for the first time a heterogeneous quantum interface between semiconductor quantum dots and a quantum memory realized in alkaline atoms. This key building block in quantum nanophotonics enables the generation of almost perfectly indistinguishable photons and near unity entanglement swapping fidelity in quantum repeater protocols. At the same time, we envision that quantum information can be encoded into the temporal envelope and phase of the single photons allowing for high capacity quantum information transfer with large alphabet.The underlying technological approach is to combine the efficient and on-demand photon generation in semiconductor quantum dots with quantum memories implemented in warm atomic vapor. The source is realized deterministically by in-situ electron beam lithography of single-QD CBR devices. Here, the advanced in-situ EBL nanotechnology platform guarantees the fabrication of QD quantum light source with well-controlled emission wavelength and high photon extraction efficiency. The memory follows a fast ladder EIT scheme in warm Cs vapor.

• DFG Programme: Research Grants
• International Connection: South Korea
• Cooperation Partner: Professor Dr. Jin-Dong Song