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Video: Cryogenic Integrated SPDC, Nina Amelie Lange, 2022

We published an extended version of this video as well, check it out here.

About us

The Mesoscopic Quantum Optics (MQO) group uses light to try and expose nonclassical phenomena at larger and larger energy scales. The most interesting and counter-intuitive consequences of quantum mechanics, for example superposition, wave-particle duality and nonlocality, are not part of our everyday experience of the world. We wish to find out what the scale limits are on phenomena like these, and whether they can be overcome. Our route to building large quantum system is to make large building blocks - fundamental quantum units that can be combined to build even larger systems. This approach combines sophisticated techniques in nonlinear optics, integrated optics and superconducting detectors, as well as theoretical techniques to deal with large data sets and develop protocols in this new, mesoscopic regime of quantum optics.

Latest publications

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Compact Metasurface-Based Optical Pulse-Shaping Device

R. Geromel, P. Georgi, M. Protte, S. Lei, T. Bartley, L. Huang, T. Zentgraf, Nano Letters (2023), 23(8), pp. 3196 - 3201

Dispersion is present in every optical setup and is often an undesired effect, especially in nonlinear-optical experiments where ultrashort laser pulses are needed. Typically, bulky pulse compressors consisting of gratings or prisms are used to address this issue by precompensating the dispersion of the optical components. However, these devices are only able to compensate for a part of the dispersion (second-order dispersion). Here, we present a compact pulse-shaping device that uses plasmonic metasurfaces to apply an arbitrarily designed spectral phase delay allowing for a full dispersion control. Furthermore, with specific phase encodings, this device can be used to temporally reshape the incident laser pulses into more complex pulse forms such as a double pulse. We verify the performance of our device by using an SHG-FROG measurement setup together with a retrieval algorithm to extract the dispersion that our device applies to an incident laser pulse.

Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry

T. Hummel, A. Widhalm, J.P. Höpker, K. Jöns, J. Chang, A. Fognini, S. Steinhauer, V. Zwiller, A. Zrenner, T. Bartley, Optics Express (2023), 31(1), 610

<jats:p>Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.</jats:p>


Electrochemical performance of KTiOAsO_4 (KTA) in potassium-ion batteries from density-functional theory

A. Bocchini, U. Gerstmann, T. Bartley, H. Steinrück, G. Henkel, W.G. Schmidt, Phys. Rev. Materials (2022), 6, pp. 105401

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Open list in Research Information System

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