Badania nad okresem póżnolateńskim i rzymskim

Zadanie pt. „Digitalizacja i udostępnienie w Cyfrowym Repozytorium Uniwersytetu Łódzkiego kolekcji czasopism naukowych wydawanych przez Uniwersytet Łódzki” nr 885/P-DUN/2014 dofinansowane zostało ze środków MNiSW w ramach działalności upowszechniającej naukę

A high-speed multi-protocol quantum key distribution transmitter based on a dual-drive modulator

We propose a novel source based on a dual-drive modulator that is adaptable and allows Alice to choose between various practical quantum key distribution (QKD) protocols depending on what receiver she is communicating with. Experimental results show that the proposed transmitter is suitable for implementation of the Bennett and Brassard 1984 (BB84), coherent one-way (COW) and differential phase shift (DPS) protocols with stable and low quantum bit error rate. This could become a useful component in network QKD, where multi-protocol capability is highly desirable.Comment: 15 pages, 7 figure

Free-running InGaAs single photon detector with 1 dark count per second at 10% efficiency

We present a free-running single photon detector for telecom wavelengths based on a negative feedback avalanche photodiode (NFAD). A dark count rate as low as 1 cps was obtained at a detection efficiency of 10%, with an afterpulse probability of 2.2% for 20 {\mu}s of deadtime. This was achieved by using an active hold-off circuit and cooling the NFAD with a free-piston stirling cooler down to temperatures of -110${^o}$C. We integrated two detectors into a practical, 625 MHz clocked quantum key distribution system. Stable, real-time key distribution in presence of 30 dB channel loss was possible, yielding a secret key rate of 350 bps.Comment: 4 pages, 4 figure

Advances in quantitative XRD analysis for clinker, cements, and cementitious additions

The Rietveld method allows a precise quantitative phase analysis of building materials. Thanks to the development of stable-functioning software and the use of high-performance detectors, a quantitative phase analysis by X-ray, including sample preparation, and measurement and evaluation, can be performed in fewer than ten minutes. This has made it possible to integrate the method into existing laboratory automation systems for process and quality control to provide a means of online monitoring. Due to the completely automated operating principle of the Rietveld software, no additional staff is required and the results are user-independent. The Rietveld method is now being employed in industrial laboratories and also in various cement plants owned by the Lafarge Group as the standard method of quantitative analysis of Portland Cement clinkers and Portland Cements (CEM I, CEM II A-L

Concise Security Bounds for Practical Decoy-State Quantum Key Distribution

Due to its ability to tolerate high channel loss, decoy-state quantum key distribution (QKD) has been one of the main focuses within the QKD community. Notably, several experimental groups have demonstrated that it is secure and feasible under real-world conditions. Crucially, however, the security and feasibility claims made by most of these experiments were obtained under the assumption that the eavesdropper is restricted to particular types of attacks or that the finite-key effects are neglected. Unfortunately, such assumptions are not possible to guarantee in practice. In this work, we provide concise and tight finite-key security bounds for practical decoy-state QKD that are valid against general attacks.Comment: 5+3 pages and 2 figure

Negative Ion Drift and Diffusion in a TPC near 1 Bar

Drift velocity and longitudinal diffusion measurements are reported for a Negative Ion TPC (NITPC) operating with Helium + carbon disulfide gas mixtures at total pressures from 160 to 700 torr. Longitudinal diffusion at the thermal-limit was observed for drift fields up to at least 700 V/cm in all gas mixtures tested. The results are of particular interest in connection with mechanical simplification of Dark Matter searches such as DRIFT, and for high energy physics experiments in which a low-Z, low density, gaseous tracking detector with no appreciable Lorentz drift is needed for operation in very high magnetic fields.Comment: 7 pages, 3 figure

Gas gain and signal length measurements with a triple-GEM at different pressures of Ar-, Kr- and Xe-based gas mixtures

We investigate the gas gain behaviour of a triple-GEM configuration in gas mixtures of argon, krypton and xenon with ten and thirty percent of carbon dioxide at pressures between 1 and 3 bar. Since the signal widths affect the dead time behaviour of the detector we present signal length measurements to evaluate the use of the triple-GEM in time-resolved X-ray imaging.Comment: 19 pages, 21 figures, revised version, accepted for publication in Nucl. Instr. and Meth.

2.23 GHz gating InGaAs/InP single-photon avalanche diode for quantum key distribution

We implement an InGaAs/InP single-photon avalanche diode (SPAD) for single-photon detection with the fastest gating frequency reported so far, of 2.23 GHz, which approaches the limit given by the bandwidth of the SPAD - 2.5 GHz. We propose a useful way to characterize the afterpulsing distribution for rapid gating that allows for easy comparison with conventional gating regimes. We compare the performance of this rapid gating scheme with free-running detector and superconducting single-photon detector (SSPD) for the coherent one-way quantum key distribution (QKD) protocol. The rapid gating system is well suited for both high-rate and long-distance QKD applications, in which Mbps key rates can be achieved for distances less than 40 km with 50 ns deadtime and the maximum distance is limited to ~190km with 5 $\mu$s deadtime. These results illustrate that the afterpulsing is no longer a limiting factor for QKD.Comment: 8 pages, 7 figures, submitted to Proceedings of SPI