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Wolfgang Fischer

Publications and source records attributed to Wolfgang Fischer.

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Cooperative Adaptive Cruise Control with Variable Time Headway for Graceful Degradation under Fluctuating Network Quality of Service

This paper proposes a dynamic distance adaptation for Cooperative Adaptive Cruise Control (CACC) under time-varying network conditions. When the Quality of Service (QoS) drops below a level required to maintain desired inter-vehicle distances, an online adaptation of the reference distances, reflected by a change of the time headway factor, becomes necessary. We present a control design algorithm realizing a graceful degradation, for which a distance control to a virtual preceding vehicle is introduced. Furthermore, the Integral Quadratic Constraints (IQC) framework is applied to guarantee robust stability of the time-varying system. The concept is validated in simulation and experimentally using small-scale test vehicles.

eess.SY

Triggered telecom C-band single-photon source with high brightness, high indistinguishability and sub-GHz spectral linewidth

Long-range, terrestrial quantum networks will require high brightness single-photon sources emitting in the telecom C-band for maximum transmission rate. Many applications additionally demand triggered operation with high indistinguishability and narrow spectral linewidth. This would enable the efficient implementation of photonic gate operations and photon storage in quantum memories, as for instance required for a quantum repeater. Especially, semiconductor quantum dots (QDs) have shown these properties in the near-infrared regime. However, the simultaneous demonstration of all these properties in the telecom C-band has been elusive. Here, we present a coherently (incoherently) optically-pumped narrow-band (0.8 GHz) triggered single-photon source in the telecom C-band. The source shows simultaneously high single-photon purity with $g^{(2)}(0) = 0.026$ ($g^{(2)}(0) = 0.014$), high two-photon interference visibility of 0.508 (0.664) and high application-ready rates of 0.75 MHz (1.45 MHz) of polarized photons. The source is based on a QD coupled to a circular Bragg grating cavity combined with spectral filtering. Coherent (incoherent) operation is performed via the novel SUPER scheme (phonon-assisted excitation).

quant-ph