Generation of indistinguishable single photons from resonantly driven semiconductor quantum dots by quantum frequency conversion to the telecom c-band

• Applicants: Professor Dr. Christoph Becher; Professor Dr. Peter Michler
• Subject Area: Experimental Condensed Matter Physics ; Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 257649910

The goal of the research project is the generation of indistinguishable single photons in the telecom C band (1550 nm) and the demonstration of a photonic quantum gate which makes use of these single photons. The generation of telecom photons is accomplished using a hybrid approach: starting point are self-organized InGaAs quantum dots embedded in planar waveguide structures emitting single photons in the near infrared (900 nm) upon optical excitation. We plan to excite the quantum dots using resonant, coherent two-photon pi-pulse excitation of the bi-exciton leading to a high degree of indistinguishability of the successively emitted photons. In a next step we convert the single photons at 900 nm via non-linear optical difference frequency generation to a wavelength of 1550 nm. As recently demonstrated in a joint effort of the applicants, the non-classical properties of the original light field are preserved during the conversion process, thus properly described as quantum frequency conversion. The important and new goal here is to test whether the indistinguishability of successively emitted photons of one and the same quantum dot is also preserved in the conversion process. Basic requirements for these experiments on one hand are reproducible fabrication of high quality InGaAs quantum dots embedded in waveguiding structures (by Institut für Halbleiteroptik und Funktionelle Grenzflächen, Universität Stuttgart) and development of portable frequency conversion setups with high efficiency and large noise suppression (by AG Quantenoptik, Universität des Saarlandes) on the other hand. Main goal of the project is quantum frequency conversion of single photons from two spatially remote, resonantly excited InGaAs quantum dots to a common wavelength within the telecom C band and demonstration of two-photon interference of the telecom photons. The small variations of the quantum dots´ emission wavelengths, naturally resulting from small variations of their geometric dimensions, are erased by frequency conversion to a common target wavelength. In a last step we demonstrate the applicability of the indistinguishable single telecom photons by implementing a quantum gate (CNOT gate) using fiber-optic components. The latter experiments are performed jointly by the two applicants´ groups. The planned experiments on deterministic generation of indistinguishable photons in the telecom band are of particular interest for scalability of future quantum information platforms.

• DFG Programme: Research Grants
• Major Instrumentation: 2x Laser, Wellenlänge: 2,2 µm
• Instrumentation Group: 5700 Festkörper-Laser