A method for demonstrating violation of local realism with a two-photon downconverter without use of Bell inequalities

We show that the recent proposal by Hardy and Jordan for a test of local realism without the use of Bell inequalities can be implemented in two-photon coincidence measurements with linear polarizers, when the photon pairs are produced by parametric downconversion. If the probabilities measured with real detectors are proportional to the corresponding probabilities determined with ideal detectors, this method does not depend on the use of detectors with high or even known quantum efficiencies.Dedicated to H. Walther on the occasion of his 60th birthday     

Teleportation of a general two-mode coherent-state superposition via attenuated quantum channels with ideal and/or threshold detectors

Three novel probabilistic yet conclusive schemes are proposed to teleport a general two-mode coherent-state superposition via attenuated quantum channels with ideal and/or threshold detectors. The calculated total success probability is highest (lowest) when only ideal (threshold) detectors are used.     

Fragmentation Cross Sections of 158 AGeV Pb Projectiles

We investigate the fragmentation cross sections of 158 AGeV ^207Pb projectile interacting with different targets using CR39 nuclear track detectors. The exposure is made at SPS beam facility of CERN. The detectors are chemically etched to obtain data in the form of etched cone length. The nuclear and electromagnetic contributions to the measured total charge-changing cross sections are investigated. The estimated results are compared with those found in the literature for similar research work.     

Low capacitance CMOS silicon photodetectors for optical clock injection

We have studied the response of CMOS compatible detectors fabricated in a silicon-on-sapphire (SOS) process, operated under short pulse excitation in the blue. These high speed, low capacitance detectors would be suitable for very precise, surface-normal clock injection with silicon CMOS. We characterize the capacitance of the detector structure through a combination of experimental techniques and circuit-level and electromagnetic simulations. The transit-time-limited response of the detectors is validated through pump–probe experiments. Detector response times of ∼35 ps have been measured, and devices have capacitance as low as ∼4 fF.     

The time recovery of the spectroscopic properties of heavily irradiated CdZnTe and CdTe detectors

The time recovery of the spectroscopic capabilities of CdZnTe and CdTe detectors, irradiated with increasing doses of high- and low-energy neutrons, as well as electrons, has been investigated by studying their spectroscopic behavior at different photon energies using leakage current measurements and PICTS (photo-induced current transient spectroscopy) analysis. The detectors were stored at room temperature for up to one year to study the time evolution of their spectroscopic performance and to correlate it with the presence of defective states in the material. We have observed a clear improvement in the material’s detection properties with time, though only in those detectors which have not been severely degraded by the irradiation. The recovery can be associated with a decrease in the concentration of some defective states, thus allowing the assessment of the crucial role these play in determining the charge collection processes in the material and its spectroscopic capabilities. Received: 1 August 2001 / Accepted: 3 August 2001 / Published online: 20 December 2001     

Relativistic Energy Pb Projectile Fragmentation with Heavy Target Nuclei

We investigate the fragmentation of 158A GeV ^207Tpb projectiles with Bi, Pb, Cu and AI targets using CR-39 nuclear track detectors. The exposures were made at SPS-CERN. After the etching, the detectors were scanned using an optical microscope to collect the data of etched cone diameters and lengths. We measured the partial charge-changing cross sections using the data of etched cone lengths. The predicted cross sections are compared to similar measurements reported in literature and their dependences on projectile and target mass are described.     

Effect of interface states on negative capacitance characteristics in GaAs homojunction far-infrared detectors

Bias-, frequency- and temperature-dependent capacitance characteristics of p-GaAs homojunction interfacial work-function internal photoemission (HIWIP) far-infrared detectors are reported. A strong negative capacitance phenomenon has been observed. The origin of this effect is believed to be due to the carrier capture and emission at interface states, and has been confirmed by a comparison study of capacitance characteristics on p-GaAs HIWIP detectors with different interface state densities. A fitting data based on charging–discharging current and the inertial conducting current model show good agreement with the experimental observations. Received: 15 November 1999 / Accepted: 20 April 2000 / Published online: 5 October 2000     

The comparison of ZnO nanowire detectors working under two wavelengths of ultraviolet

Schottky-barrier ultraviolet (UV) detectors based on ZnO-nanowires (NWs) were fabricated with Pt as electrodes in this investigation. The ZnO NWs synthesized by the hydrothermal method were characterized by field-emission scanning electron microscopy (FE-SEM), Raman and PL spectroscopy. Photoelectric properties under 254 and 365 nm UV light were investigated. It is found that the photo-response properties of the devices under 365 nm UV light are better than those under 254 nm UV light, which is further illustrated by light transmission theory, energy-band diagram and absorption spectra. The results demonstrate that ZnO NWs detectors with selectivity to near-UV (NUV) light are promising candidates in photoelectric devices.     

Rapid structure determination of disordered materials: study of GeSe2 glass

X-ray diffraction experiments on GeSe₂ glass employing an Imaging Plate detector system have been carried out and their performance compared to that of traditional experiments employing point-type detectors. Imaging Plate detectors have been found to perform very well delivering good quality data for just a second. The analysis of the experimental data shows that the atomic ordering in GeSe₂ glass bears many of the characteristics of a random network of Ge-Se₄ tetrahedra.     

In-beam gamma-ray spectroscopy with exotic beams at the NSCL

Projectile fragmentation provides radioactive beams at intermediate velocities (v/c = 0.3-0.5) by physical means of fragment separation. With the development of position-sensitive photon detectors it has become possible to measure the energies and directions of photons emitted in-flight from such fast-moving exotic beams. This allows the reconstruction of the photons' energies emitted from an exotic projectile with high accuracy. It can be advantageous to employ photon detection in experiments with exotic beams since photons can traverse matter easily and their attenuation can be calculated. Experiments with standard luminosities can be carried out at intermediate beam energies with thick secondary targets (order of g/cm²) and very low incident beam rates (order of particle/s or less). Experimental success in this field is strongly correlated with the development of photon detectors such as position-sensitive scintillation detectors or segmented germanium detectors. In-beam gamma-ray spectroscopy of fast exotic beams has been successfully used at all projectile fragmentation facilities in intermediate-energy heavy-ion inelastic scattering experiments, knockout reactions and fragmentation reactions. Here, we focus on experimental results for neutron-rich exotic nuclei in the π(sd )-shell. Measurements and detector developments carried out at the NSCL at Michigan State University during the last four years are discussed. Received: 1 May 2001 / Accepted: 4 December 2001     

Detection

This review on second- and third-generation multidetectors devoted to heavy-ion collisions aims to cover the last twenty years. The presented list of devices is not exhaustive but regroups most of the techniques used during this period for nuclear reactions at intermediate energy (≃ 10A MeV to 1A GeV), both for charged-particle and neutron detection. The main part will be devoted to 4π multidetectors, projectile decay fragmentation, high-resolution magnetic spectrometers, auxiliary detectors and neutron detection. The last part will present the progress in electronics and detection in view of the construction of future-generation detectors.     

Current programs of search for gravitational waves by terrestrial detectors

We discuss the problem of of detection the gravitational radiation which could be produced by relativistic objects in the Universe. After a brief sketch of the detector world net the attention is concentrated on present programs of search for conceivable signals expected in the frame of modern astrophysics. It is concluded that the probability of succeeding with the modern generation of gravitational detectors, sensitive to the metric perturbation on the order of 10⁻²¹, is low. One of the ways to increase the probability is a search for “astro-gravity correlations” where a gravitational detector noise background is analysed referring to the data of gamma-ray and neutrino detectors. Author dedicates this article to Prof. Jiří Bičák’s 60th birthday.     

A novel nondeterministic scheme for a nondestructive two-qubit controlled phase gate with linear optics

A linear optical scheme for realizing the nondeterministic two-qubit quantum controlled phase gate is presented. The proposed setup involves a pair of product states, polarizing beam splitters, phase shifters and photon number resolving detectors. The omission of entangled ancilla input and additional single-qubit operations significantly reduces the complexity of this gate. This can be well implemented in experiment.     

Thermally stimulated current and high temperature resistivity measurements of 4H semi-insulating silicon carbide

High purity semi-insulating 4H SiC single crystals have potential applications for room temperature radiation detectors because of the wide band gap and radiation hardness. To control carrier lifetime, a key parameter for high performance radiation detectors, it is important to understand the nature of the deep traps in this material. For this purpose, we have successfully applied thermally stimulated current (TSC) and high temperature resistivity measurements to investigate deep level centers in semi-insulating 4H SiC samples grown by physical vapor transport. High temperature resistivity measurements showed that the resistivity at elevated temperatures is controlled by the deep level with an activation energy of 1.56 eV. The dominant traps revealed by TSC measurements were at 1.1-1.2 eV. The deep trap levels in 4H-SiC samples, the impurity and point defect nature of TSC traps peaked at ∼106 K (0.23 eV), ∼126 K (0.32 eV), ∼370 K (0.95 eV), ∼456 K (1.1-1.2 eV) are discussed.     

Chaos in photovoltaic HgCdTe detectors under laser irradiation

Chaos in photovoltaic HgCdTe detectors irradiated by a low-power stable continuous-wave laser is found in our experiment. The detectors give a chaotic output in the laser irradiation power density range a little higher than their saturation threshold. Chaos is diagnosed by calculating the power spectrum and the Lyapunov exponent with experimental data of the detectors’ output signals vs. time. We conclude with a qualitative discussion of the possible causes of the observed chaotic behavior. Received: 3 April 2002 / Revised version: 8 July 2002 / Published online: 25 October 2002 RID="*" ID="*"Corresponding author. (Fax: +86-0731/4514127, E-mail: maliqin01@263.net)     

Distillation of continuous-variable entanglement with optical means

We present an event-ready procedure that is capable of distilling Gaussian two-mode entangled states from a supply of weakly entangled states that have become mixed in a decoherence process. This procedure relies on passive optical elements and photon detectors distinguishing the presence and the absence of photons, but does not make use of photon counters. We identify fixed points of the iteration map, and discuss in detail its convergence properties. Necessary and sufficient criteria for the convergence to two-mode Gaussian states are presented. On the basis of various examples we discuss the performance of the procedure as far as the increase of the degree of entanglement and two-mode squeezing is concerned. Finally, we consider imperfect operations and outline the robustness of the scheme under non-unit detection efficiencies of the detectors. This analysis implies that the proposed protocol can be implemented with currently available technology and detector efficiencies.     

On the necessity of light transport simulation in scintillators

In this study, the light transport simulation in scintillators is introduced, the wavelength-dependencies in the process are taken into account, the effect of different shapes/lengths of lightguides on the response of the scintillation detectors are investigated and finally the need for such a simulation in addition to the particle transport simulation in a perfect response function predicting code is explained.     

Purity and entanglement of two-photon polarization states generated by spontaneous parametric down-conversion

We elucidate the dependence of purity and entanglement of two-photon states generated by spontaneous parametric down-conversion on the parameters of the source, such as crystal length, pump beam divergence, frequency bandwidth, and detectors angular aperture. The effect of crystal anisotropy is taken into account. Numerical simulations are presented for two types of commonly used source configurations.     

A linear optical protocol of random quantum key distribution by using polarization entangled photons

Utilized polarization entangled photons, a linear optical protocol for generating random quantum key distribution (QKD) is proposed, which is made up of EPR-source, linear optical elements, and conventional photon detectors. It is shown that total efficiency of QKD η=100% in theory.     

Dielectric properties and potential applications of nanocrystal networks

Nanocrystal networks, especially mixtures of chemically different components or gradient materials, may turn out to be absorbers, sensors, detectors, or converters, designed for a variety of specific purposes with high sensitivity and flexibility. Received: 27 March 1998