Phase Noise in Real-World Twin-Field Quantum Key Distribution

We investigate the impact of noise sources in real-world implementations of Twin-Field Quantum Key Distribution (TF-QKD) protocols, focusing on phase noise from photon sources and connecting fibers. Our work emphasizes the role of laser quality, network topology, fiber length, arm balance, and detector performance in determining key rates. Remarkably, it reveals that the leading TF-QKD protocols are similarly affected by phase noise despite different mechanisms. Our study demonstrates duty cycle improvements of over 2x through narrow-linewidth lasers and phase-control techniques, highlighting the potential synergy with high-precision time/frequency distribution services. Ultrastable lasers, evolving toward integration and miniaturization, offer promise for agile TF-QKD implementations on existing networks. Properly addressing phase noise and practical constraints allows for consistent key rate predictions, protocol selection, and layout design, crucial for establishing secure long-haul links for the Quantum Communication Infrastructures under development in several countries.Comment: 18 pages, 8 figures, 2 table

Corrugated Waveguide Slow-Wave Structure for THz Travelling Wave Tube

THz applications require sources and amplifiers compact, lightweight and powerful. Vacuum electron devices are the candidate solution. Among others, the Corrugated Waveguide Slow-Wave Structure seems particularly suitable for Traveling Wave Tubes in the THz region. THz vacuum electron devices require high precision technological processes with high aspect ratio such as SU-8 process. However, fabrication tolerances could highly affect the overall performances. Therefore a statistical analysis is fundamental for a reliable design. In this summary it is proposed a method based on an analytical model of the corrugated waveguide together with the Pierce theory, to fastly compute the gain of corrugated waveguide vacuum traveling wave tubes. The method is validated by three-dimensional electromagnetic softwares, both for cold and hot parameters. The proved accuracy and fast computation time make the model suitable for performing the sensitivity analysis of the Corrugated waveguide Vacuum tube to be realized by SU-8 technology process

Packaged Single Pole Double Thru (SPDT) and True Time Delay Lines (TTDL) Based on RF MEMS Switches

Packaged MEMS devices for RF applications have been modelled, realized and tested. In particular, RF MEMS single ohmic series switches (SPST) have been obtained on silicon high resistivity substrates and they have been integrated in alumina packages to get single-pole-double-thru (SPDT) and true-time-delayline (TTDL) configurations. As a result, TTDLs for wide band operation, designed for the (6-18) GHz band, have been obtained, with predicted insertion losses less than 2 dB up to 14 GHz for the short path and 3 dB for the long path, and delay times in the order of 0.3-0.4 ns for the short path and 0.5-0.6 ns for the long path. The maximum differential delay time is in the order of 0.2 ns

Antenna-coupled heterostructure field effect transistors for integrated terahertz heterodyne mixers

We present the realization of high electron mobility transistors on GaN-heterostructures usable for mixing and rectification in the THz range. Device fabrication is fully compatible with industrial processes employed for millimetre wave integrated circuits. On-chip, integrated, polarization- sensitive, planar antennas were designed to allow selective coupling of THz radiation to the three terminals of field effect transistors in order to explore different mixing schemes for frequencies well above the cutoff frequency for amplification. The polarization dependence of the spectral response in the 0.18-0.40 THz range clearly demonstrated the possible use as integrated heterodyne mixers. © 2013 Copyright SPIE

Development and characterization of xyloglucan-poly(vinyl alcohol) hydrogel membrane for Wireless Smart wound dressings

Hydrogel-based smart wound dressings that combine the traditional favourable properties of hydrogels as skin care materials with sensing functions of relevant biological parameters for the remote monitoring of wound healing are under development. In particular, lightweight, ultra-high frequency radiofrequency identification (UHF RFID) sensor are adjoined to xyloglucan-poly(vinyl alcohol) hydrogel films to battery-less monitor moisture level of the bandage in contact with the skin, as well as wireless transmit the measured data to an off-body reader. This study investigates the swelling behavior of the hydrogels in contact with simulated biological fluids, and the modification of their morphology, mechanical properties, and dielectric properties in a wide range of frequencies (100–106 Hz and 108–1011 Hz). The films absorb simulated body fluids up to approximately four times their initial weight, without losing their integrity but undergoing significant microstructural changes. We observed relevant linear increases of electric conductivity and permittivity with the swelling degree, with an abrupt change of slope that is related to the network rearrangements occurring upon swelling