Deterministic solid state quantum light sources are considered key building blocks for future communication networks. While several proof-of-principle experiments of quantum communication using such sources have been realized, most of them required large setups—often involving liquid helium infrastructure or bulky closed-cycle cryotechnology. In this work, we report on the first quantum key distribution (QKD) testbed using a compact benchtop quantum dot single-photon source operating at telecom wavelengths. The plug&play device emits single-photon pulses at O-band wavelengths (1321 nm) and is based on a directly fiber-pigtailed deterministically fabricated quantum dot device integrated into a compact Stirling cryocooler. The Stirling is housed in a 19 in. rack module including all accessories required for stand-alone operation. Implemented in a simple QKD testbed emulating the BB84 protocol with polarization coding, we achieve an multiphoton suppression of g(2)(0)=0.10±0.01 and a raw key rate of up to (4.72 ± 0.13) kHz using an external pump laser. In this setting, we further evaluate the performance of our source in terms of the quantum bit error ratios, secure key rates, and tolerable losses expected in full implementations of QKD while accounting for finite key size effects. Furthermore, we investigate the optimal settings for a two-dimensional temporal acceptance window applied on the receiver side, resulting in predicted tolerable losses up to 23.19 dB. Not least, we compare our results with previous proof-of-concept QKD experiments using quantum dot single-photon sources. Our study represents an important step forward in the development of fiber-based quantum-secured communication networks exploiting sub-Poissonian quantum light sources.
It is part of the standard repertoire of Eulenspiegel research to point out that the jest novel Ein kurtzweilig Lesen von Dil Ulenspiegel (1510/15) places a highly contradictory protagonist of heterogenous motivations at the centre of its plot, which oscillates between vita and episode sequence. Rarely, however, have the instruments of structuralist narratology been used systematically to investigate how this heterogeneity and contradiction comes about and what strategies the text uses to connect the individual episodes. Using the example of the recurring element of ‘falling bodies’, this article analyzes the eventfulness, the production of coherence and the function of certain action patterns in the individual episodes. One central hypothesis of this article is that by means of recurrence and variation falling bodies establish a literary paradigm in the novel keeping a central theme of the text present: the dissociation of a superior protagonist who eludes the demands of the community on his body.
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We report on BB84 quantum key distribution tests employing a benchtop plug&play quantum-dot based single-photon source operating at O-band wavelengths. We perform a detailed characterization and exploit optimized temporal filters to maximize the tolerable losses.
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