High-speed device-independent quantum key distribution against collective attacks

The security of quantum key distribution (QKD) usually relies on that the users’s devices are well characterized according to the security models made in the security proofs. In contrast,device-independent QKD an entanglement-based protocol permits the security even without any knowledge of the underlying devices. Despite its beauty in theory, device-independent QKD is elusive to realize with current technology. This is because a faithful realization requires ahigh-quality violation of Bell inequality without the fair-sampling assumption. Particularly, in a photonic realization, a rather high detection efficiency is needed where the threshold values depend on the security proofs; this efficiency is far beyond the current reach. Here, both theoretical and experimental innovations yield the realization of device-independent QKD based on a photonic setup. On the theory side, to relax the threshold efficiency for practical deviceindependent QKD, we exploit the random post-selection combined with adding noise for preprocessing, and compute the entropy with complete nonlocal correlations. On the experiment side, we develop a high-quality polarization-entangled photonic source and achieve state-of-theart (heralded) detection efficiency of 87.49%, which outperforms previous experiments and satisfies the threshold efficiency for the first time. Together, we demonstrate device-independent QKD at a secret key rate of 466 bits/s over 20 m standard fiber in the asymptotic limit against collective attacks. Besides, we show the feasibility of generating secret keys at a fiber length of 220 meters. Importantly, our photonic implementation can generate entangled photons at a high rate and in the telecom wavelength, which is desirable for high-speed key generation over long distances. The results not only prove the feasibility of device-independent QKD with realistic devices, but also push the security of communication to an unprecedented level.

Neutrinoless Double Beta Decay with Germanium Detectors: 1026 yr and Beyond

In the global landscape of neutrinoless double beta (0νββ) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the 76Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive 0νββ decay search. The Majorana and Gerda experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of 2.53 ± 0.08 keV at the Qββ and an unprecedented low background level of 5.2×10−4 cts/(keV·kg·yr), respectively. In this paper, we will review the path of 0νββ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the Gerda experiment setting a limit on the half-life of 76Ge 0νββ decay at T1/2>1.8×1026 yr (90% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to 1028 yr and beyond, opening the way to the exploration of the normal ordering region.

MBGEM: a stack of borated GEM detector for high efficiency thermal neutron detection

A new position-sensitive thermal neutron detector based on boron-coated converters has been developed as an alternative to today’s standard $$^3\mathrm{He}$$ 3 He -based technology for application to thermal neutron scattering. The key elements of the development are the boron-coated GEM foils (Sauli in Nucl Instrum Methods Phys Res Sect A Accel Spectrom Detect Assoc Equip 386:531, 1997) that are used as a multi-layer neutron converter via the $$^{10}\mathrm{B}(n,\alpha )^7\mathrm{Li}$$ 10 B ( n , α ) 7 Li reaction together with an efficient collection of the produced secondary electrons. This paper reports the test performed on a 3 layers converter prototype coupled to a GEMPix detector (Murtas in Radiat Meas 138:106421, 2020), carried out in order to study the possibility to produce a large-scale multi-layer neutron detector capable to reach high detection efficiency with high spatial resolution and able to sustain the high neutron flux expected in the new neutron spallation source under development like the ESS.

Data Authentication for Wireless Sensor Networks with High Detection Efficiency Based on Reversible Watermarking

Data authentication is an important part of wireless sensor networks (WSNs). Aiming at the problems of high false positive rate and poor robustness in group verification of existing reversible watermarking schemes in WSNs, this paper proposes a scheme using reversible watermarking technology to achieve data integrity authentication with high detection efficiency (DAHDE). The core of DAHDE is dynamic grouping and double verification algorithm. Under the condition of satisfying the requirement of the group length, the synchronization point is used for dynamic grouping, and the double verification ensures that the grouping will not be confused. According to the closely related characteristics of adjacent data in WSNs, a new data item prediction method is designed based on the prediction-error expansion formula, and a flag check bit is added to the data with embedded watermarking during data transmission to ensure the stability of grouping, by which the fake synchronization point can be accurately identified. Moreover, the embedded data can be recovered accurately through the reversible algorithm of digital watermarking. Analysis and experimental results show that compared with the previously known schemes, the proposed scheme can avoid false positive rate, reduce computation cost, and own stronger grouping robustness.

A Simulation of a Novel High Quantum Efficiency Scintillating Fiber Detector with Anti-scatter Properties for Megavoltage X-Ray Imaging

To further develop a MV x-ray portal imaging device with high detection efficiency and adequate spatial resolution for image guided radiation therapy, the experimental results for a prototype detector were matched using Monte-Carlo software to then improve upon the design. The simulation and experiment were carried out using a 6 MV beam from a linear accelerator machine. An adequate match was obtained with the spatial resolution matching up to a MTF value of 0.2 and then diverging and the total signal registered in the central fiber was matched for field sizes ranging from 3 cm by 3 cm to 20 cm by 20 cm for 5 cm, 15 cm and 25 cm air gaps within 3%. The design was altered from a hexagonal array of round double cladded fibers to a square array of single cladded square fibers. The spatial resolution was improved from 0.242 lp mm-1 to 0.359 lp mm-1 at an MTF value of 0.5 from the original design to a square array of square fibers 0.5 mm wide separated by 0.25 mm of lead foil. With further optimization of the detector design it may be possible to increase spatial resolution for MV x-ray imaging while maintaining an adequate detection efficiency.

A Simulation of a Novel High Quantum Efficiency Scintillating Fiber Detector with Anti-scatter Properties for Megavoltage X-Ray Imaging

To further develop a MV x-ray portal imaging device with high detection efficiency and adequate spatial resolution for image guided radiation therapy, the experimental results for a prototype detector were matched using Monte-Carlo software to then improve upon the design. The simulation and experiment were carried out using a 6 MV beam from a linear accelerator machine. An adequate match was obtained with the spatial resolution matching up to a MTF value of 0.2 and then diverging and the total signal registered in the central fiber was matched for field sizes ranging from 3 cm by 3 cm to 20 cm by 20 cm for 5 cm, 15 cm and 25 cm air gaps within 3%. The design was altered from a hexagonal array of round double cladded fibers to a square array of single cladded square fibers. The spatial resolution was improved from 0.242 lp mm-1 to 0.359 lp mm-1 at an MTF value of 0.5 from the original design to a square array of square fibers 0.5 mm wide separated by 0.25 mm of lead foil. With further optimization of the detector design it may be possible to increase spatial resolution for MV x-ray imaging while maintaining an adequate detection efficiency.

Designing and setting up the scintillationdetector using CsI(Tl) crystals and avalanche photodiode for gamma-ray measurement

Localization of the scintillation detectors manufacturing process has many benefits because of the high detection efficiency of the detectors, user-friendly, and consistent with general research objectives. Using a photodiode instead of a photomultiplier tube (PMT) allows saving energy, shortening the detector volume, and removing high voltage power supply and amplifier. The combination of CsI(Tl) scintillator, avalanche photodiode, charge sensitive preamplifier, wide range amplifier, and power supply system has been integrated into the detector. This study presents new results in manufacturing a home-made scintillation detector using avalanche photodiode. The detectors of this type can be used in hospitals, in the nuclear laboratory of universities for the students training, etc.