Detector Side Research Articles

(Invited) Inkjet-Printed Terahertz Detector

Terahertz waves have shown promise for a number of applications but challenges in developing sources and detectors in this frequency range have prevented broader adoption of the technology. On the detector side, recent work has focused on developing imaging arrays and in improving their performance, which often requires cooling of devices made by photolithography on rigid substrates. Here we present a different approach that focuses on room-temperature detection using inkjet-printed carbon nanotube (CNT) devices. The inkjet printing approach allows for facile, on-the-fly design and printing of devices, including in array format. The structural flexibility of the devices opens new avenues for imaging in non-planar geometries. In this presentation, I will discuss the challenges in developing and printing CNT inks for this particular application, and their properties in the THz. Results of THz detection of CNT pixel arrays will be presented, as well as the factors that impact performance.

One-sided measurement-device-independent quantum key distribution

Measurement-device-independent quantum key distribution (MDI-QKD) protocol was proposed to remove all the detector side channel attacks, while its security relies on the trusted encoding systems. Here we propose a one-sided MDI-QKD (1SMDI-QKD) protocol, which enjoys detection loophole-free advantage, and at the same time weakens the state preparation assumption in MDI-QKD. The 1SMDI-QKD can be regarded as a modified MDI-QKD, in which Bob's encoding system is trusted, while Alice's is uncharacterized. For the practical implementation, we also provide a scheme by utilizing coherent light source with an analytical two decoy state estimation method. Simulation with realistic experimental parameters shows that the protocol has a promising performance, and thus can be applied to practical QKD applications.

Upgrade of the compact neutron spectrometer for high flux environments

In this paper new version of the 6Li-based neutron spectrometer for high flux environments is described. The new spectrometer was built with commercial single crystal Chemical Vapour Deposition diamonds of electronic grade. These crystals feature better charge collection as well as higher radiation hardness. New metal contacts approaching ohmic conditions were deposited on the diamonds suppressing build-up of space charge observed in the previous prototypes. New passive preamplification of the signal at detector side was implemented to improve its resolution. This preamplification is based on the RF transformer not sensitive to high neutron flux. The compact mechanical design allowed to reduce detector size to a tube of 1 cm diameter and 13 cm long. The spectrometer was tested in the thermal column of TRIGA reactor and at the DD neutron generator. The test results indicate an energy resolution of 300 keV (FWHM), reduced to 72 keV (RMS) excluding energy loss, and coincidence timing resolution of 160 ps (FWHM). The measured data are in agreement with Geant4 simulations except for larger energy loss tail presumably related to imperfections of metal contacts and glue expansion.

Decoy-State Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution With Biased Bases

Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) can eschew the alignment of reference frames in practical systems and defeat all potential detector side channel attacks. Here, we propose the decoy-state RFI-MDI-QKD protocol with biased bases. In this protocol, two legitimate parties Alice and Bob prepare signal states in $Z$ , $X$ , and $Y$ bases and decoy states in $X$ and $Y$ bases, which avoids the futility in $Z$ basis for decoy states and simplifies the operation of existing systems. Considering the security against coherent attacks with statistical fluctuations, we investigate the performance of the decoy-state RFI-MDI-QKD protocol with biased bases in the environment of unknown and slowly drifting reference frames and make comparisons with the original decoy-state RFI-MDI-QKD protocol under the same conditions. Simulation results show that the proposed protocol can increase the achievable secret key rate and transmission distance obviously compared with the original protocol, which is very promising in real-life QKD systems.

Introducing a Novel Parallel Hole Collimator: The Theoretical and Monte Carlo Investigations

To assess function of various organs as well as recognize malignancy in its initial stages, single photon emission computed tomography system is employed in which the collimators can obtain the qualified images toward better diagnostic on the lesions and metabolic performance. Although new designs and optimized methods as well as the analytical models have been proposed to improve tradeoff between resolution and sensitivity in the collimators, but opposing behavior of them still remains as one of the major problems associated with the parallel hole collimators (PCs). In this paper, a new design, namely, extended parallel hole collimator (EPC) in which trapezoidal denticles are added upon the collimator septa at the detector side, has been proposed to improve performance of the PCs. Two PCs as PC35 and PC41 with hole sizes of 1.5 mm and hole lengths of 35 and 41 mm, respectively, are considered for comparison and investigation of the EPC performance. Theory and Monte Carlo simulations have been carried out to evaluate some of its related parameters such as sensitivity, resolution, and contrast. To reconstruct the tomographic images of Jaszczak phantom, the maximum-likelihood expectation maximization algorithm is chosen. The results have been indicated that the EPC has increased the amount of sensitivity as 10.2% compared to the PCs at the same resolution, and decreased the penetrating ratio as well as produced the tomographic images with lower noise coefficient (NC%), and improved contrast to noise ratio. Finally, it is found that the EPC may obtain the qualified images.

Measurement-device-independent quantum key distribution robust against environmental disturbances

Measurement-device-independent quantum key distribution (MDI QKD) is a promising protocol for removing all detector side channel attacks. However, the variation of reference frames, e.g., polarization and phase reference, would be an acute threat to the performance of MDI systems. Here, based on polarization scrambling units, we demonstrate a reference-frame-independent MDI QKD scheme that is inherently stable against volatile channel conditions; therefore, the final secure key rate will be insensitive to the random disturbances of polarization and the drifts of phase reference. Thus, calibrations of the primary reference frames are intrinsically removed in our scheme, which essentially reduces potential vulnerabilities as well as the resource consumption of the whole system. In addition, a proof-of-principle experiment with an improved fluctuation analysis method is demonstrated to verify the feasibility and advantages of the proposed scheme.

Fluctuations of Internal Transmittance in Security of Measurement-Device-Independent Quantum Key Distribution with an Untrusted Source**Supported by the National Basic Research Program of China under Grant No. 2013CB338002 and the National Natural Science Foundation of China under Grant Nos. 61505261, 61675235, 61605248, 11304397

Measurement-device-independent quantum key distribution (MDI-QKD) is immune to detector side channel attacks, which is a crucial security loophole problem in traditional QKD. In order to relax a key assumption that the sources are trusted in MDI-QKD, an MDI-QKD protocol with an untrusted source has been proposed. For the security of MDI-QKD with an untrusted source, imperfections in the practical experiment should also be taken into account. In this paper, we analyze the effects of fluctuations of internal transmittance on the security of a decoy-state MDI-QKD protocol with an untrusted source. Our numerical results show that both the secret key rate and the maximum secure transmission distance decrease when taken fluctuations of internal transmittance into consideration. Especially, they are more sensitive when Charlie’s mean photon number per pulse is smaller. Our results emphasize that the stability of correlative optical devices is important for practical implementations.

In situ observation and numerical simulation of bubble behavior in CaO-SiO2 based slag during isothermal and nonisothermal processes

The hot thermocouple technique was used to observe the variation of bubble size in CaO-SiO2 based molten slag at above 1273K. Considering that the physical properties of gases change with temperature, the effect of cooling rate on the single bubble behavior was studied according to the heat and mass transfer equations. In order to investigate the distribution of pore size in solidified layer, solidification of slag was conducted in laboratory by using a water-cooled detector, and the pore size in the solidified layer was counted under the scanning electron microscope. The heat flux measured by the water-cooled detector was used as boundary conditions to establish a mathematical model that is capable of describing the characteristics of bubble size distribution. Both the calculation and the observations indicate that the time-temperature history is an important factor that could affect the bubble behavior in molten slag. For slag with no Na2SO4, bubbles with large size concentrate on the detector side with high cooling rate, while bubbles with small size are likely to appear on the liquid side with low cooling rate. For slags containing Na2SO4, bubbles with large size mainly distribute on the middle layer of the solid slag film.

Practical decoy-state reference-frame-independent measurement-device-independent quantum key distribution

Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) is proposed to remove all possible detector side channel attacks without the alignment of reference frames. Due to unavoidable multiphoton events in practical sources, the decoy-state method is always adopted in real-life QKD systems. Unlike original MDI-QKD (O-MDI-QKD), the characterization on practical decoy-state RFI-MDI-QKD is still absent to date. In this paper, we investigate the performance of practical decoy-state RFI-MDI-QKD at different misalignments of reference frames with full parameter optimization when considering statistical fluctuations, and provide a clear comparison between decoy-state RFI-MDI-QKD and O-MDI-QKD. Simulation results demonstrate that decoy-state RFI-MDI-QKD can exhibit performance comparable to that of O-MDI-QKD in practical scenarios, which is very robust in QKD systems.

Continuous-Variable Measurement-Device-Independent Multipartite Quantum Communication Using Coherent States

A continuous-variable measurement-device-independent (CV-MDI) multipartite quantum communication protocol is designed to realize multipartite communication based on the GHZ state analysis using Gaussian coherent states. It can remove detector side attack as the multi-mode measurement is blindly done in a suitable Black Box. The entanglement-based CV-MDI multipartite communication scheme and the equivalent prepare-and-measurement scheme are proposed to analyze the security and guide experiment, respectively. The general eavesdropping and coherent attack are considered for the security analysis. Subsequently, all the attacks are ascribed to coherent attack against imperfect links. The asymptotic key rate of the asymmetric configuration is also derived with the numeric simulations illustrating the performance of the proposed protocol.

Evolution of Temperature and Solid Slag Film During Solidification of Mold Fluxes

A mathematical model based on one-dimensional transient heat conduction was developed to calculate temperature distribution of slag film during cooling process. Solid slag film was obtained from a water-cooled copper detector, and the evolution of its structure was analyzed according to the calculated results and crystallization behavior of mold fluxes. During formation process of the solid slag film, the cooling rate of liquid slag first increases, and then decreases with time. The maximum value of the cooling rate may exceed 50 K/s. Before the solid slag film is formed, the cooling rate of molten slag on the detector side is much higher than that of slag on the liquid slag side. Experimental results indicate that the thermal history of a cooling process has an effect on the crystallization temperature of mold flux. In addition, variation of temperature can also influence the structure of solid slag film since the increase of temperature inside the slag film may lead to the crystallization of the glassy layer.

Loss-tolerant measurement-device-independent quantum private queries

Quantum private queries (QPQ) is an important cryptography protocol aiming to protect both the user’s and database’s privacy when the database is queried privately. Recently, a variety of practical QPQ protocols based on quantum key distribution (QKD) have been proposed. However, for QKD-based QPQ the user’s imperfect detectors can be subjected to some detector- side-channel attacks launched by the dishonest owner of the database. Here, we present a simple example that shows how the detector-blinding attack can damage the security of QKD-based QPQ completely. To remove all the known and unknown detector side channels, we propose a solution of measurement-device-independent QPQ (MDI-QPQ) with single- photon sources. The security of the proposed protocol has been analyzed under some typical attacks. Moreover, we prove that its security is completely loss independent. The results show that practical QPQ will remain the same degree of privacy as before even with seriously uncharacterized detectors.

Non Regenerative Fiber backbone Power Loss Budget

The most important stage in the design of a Wavelength Division Multiplexing (WDM) fiber optic system is about the choice of the correct optical transmitter, and receiver combination. This depends on the signal to be transmitted over the channel. By adopting the WDM two (2) signals at two (2) different wavelengths of 1310nm and 1550nm, can conveniently be carried on the same fiber. The WDM fiber link can carry 32,256 channels and the throughput too is high (>=2.5Gbps). Many television channels can be accommodated. The amplification along the fiber backhaul remains a bottleneck due to the non-linearity effects that could be additive. In order to minimize the non-linearity effect of the amplifiers, non-regenerative solutions are nowadays used.This paper develops a power loss budget for an optical sparse WDM long haul without inserting any regenerator along the transmission line. The study gives details of establishing a 200 km fiber optic link, operating at 2.5Gbps and supporting a digital signal of Synchronous Transport signal-48/ Synchronous Transport Module 16 (STS-48/STM-16). The link is assumed to carry 8 (WDM). In the dimensioning, the optical interfaces were chosen in agreement with the ITU-T G 654 applicable values. The system power deficit was not satisfactory in the first attempt. Then, the Erbium Doped-Fiber Amplifiers (EDFA) were inserted at the light source, and a preamplifier at the optical detector side. The system power deficit was still negative but not much. The transmitting system should have a positive value of the system power deficit so that the link budget can be suggested for the required transmission. Finally the change of the detector sensitivity gave the best estimation in the design process for the required link budget.

Tomographic Approach in Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution**Supported by the National Basic Research Program of China under Grant Nos. 2011CBA00200 and 2011CB921200, the National Natural Science Foundation of China under Grant Nos. 61475148, 61575183, and the “Strategic Priority Research Program (B)” of the Chinese Academy of Sciences under Grant Nos. XDB01030100, XDB01030300

Recently, a novel reference-frame-independent measurement-device-independent quantum key distribution protocol was proposed, which can remove all detector side channels as well as tolerate unknown and slow variance of reference frame without active alignment. In this paper, we propose a new tomographic method to estimate the key rate in that protocol. We estimate the key rate using conventional method and tomographic method respectively and compare the two methods by numerical simulation. The numerical simulation results show that tomographic approach is equivalent to the conventional approach, which can be used as an alternative method.

Quantum key distribution with prepare-and-measure Bell test

The prepare-and-measure quantum key distribution (QKD) has the merits of fast speed, high key generation rate, and easy implementation. However, the detector side channel attacks greatly undermine the security of the key bits. The eavesdropper, Eve, exploits the flaws of the detectors to obtain illegal information without violating quantum principles. It means that she can intervene in the communication without being detected. A prepare-and-measure Bell test protocol will be proposed. By randomly carrying out Bell test at the side of the information receiver, Bob, Eve’s illegal information gain within the detector side channel attack can be well bounded. This protocol does not require any improvement on the detectors used in available prepare-and-measure QKD. Though we only illustrate its application in the BB84 protocol, it is applicable for any prepare-and-measure QKD.

Measurement-Device-Independent Quantum Key Distribution with Two-Way Local Operations and Classical Communications**Supported by the National Natural Science Foundation of China under Grant No 61378011, and the Program for Science and Technology Innovation Research Team in University of Henan Province under Grant No 13IRTSTHN020.

Measurement-device-independent quantum key distribution (MDI-QKD) is proven to be immune to all the detector side channel attacks. With two symmetric quantum channels, the maximal transmission distance can be doubled when compared with the prepare-and-measure QKD. An interesting question is whether the transmission distance can be extended further. In this work, we consider the contributions of the two-way local operations and classical communications to the key generation rate and transmission distance of the MDI-QKD. Our numerical results show that the secure transmission distances are increased by about 12 km and 8 km when the 1 B and the 2 B steps are implemented, respectively.

Reducing the influence of direct reflection on return signal detection in a 3D imaging lidar system by rotating the polarizing beam splitter

The direction rule of the laser beam traveling through a deflected polarizing beam splitter (PBS) cube is derived. It reveals that, due to the influence of end-face reflection of the PBS at the detector side, the emergent beam coming from the incident beam parallels the direction of the original case without rotation, with only a very small translation interval between them. The formula of the translation interval is also given. Meanwhile, the emergent beam from the return signal at the detector side deflects at an angle twice that of the PBS rotation angle. The correctness has been verified by an experiment. The intensity transmittance of the emergent beam when propagating in the PBS is changes very little if the rotation angle is less than 35 deg. In a 3D imaging lidar system, by rotating the PBS cube by an angle, the direction of the return signal optical axis is separated from that of the origin, which can decrease or eliminate the influence of direct reflection caused by the prism end face on target return signal detection. This has been checked by experiment.

JPSS-1 VIIRS Pre-Launch Response Versus Scan Angle Testing and Performance

The Visible Infrared Imaging Radiometer Suite (VIIRS) instruments on-board both the Suomi National Polar-orbiting Partnership (S-NPP) and the first Joint Polar Satellite System (JPSS-1) spacecraft, with launch dates of October 2011 and December 2016 respectively, are cross-track scanners with an angular swath of ±56.06°. A four-mirror Rotating Telescope Assembly (RTA) is used for scanning combined with a Half Angle Mirror (HAM) that directs light exiting from the RTA into the aft-optics. It has 14 Reflective Solar Bands (RSBs), seven Thermal Emissive Bands (TEBs) and a panchromatic Day Night Band (DNB). There are three internal calibration targets, the Solar Diffuser, the BlackBody and the Space View, that have fixed scan angles within the internal cavity of VIIRS. VIIRS has calibration requirements of 2% on RSB reflectance and as tight as 0.4% on TEB radiance that requires the sensor’s gain change across the scan or Response Versus Scan angle (RVS) to be well quantified. A flow down of the top level calibration requirements put constraints on the characterization of the RVS to 0.2%–0.3% but there are no specified limitations on the magnitude of response change across scan. The RVS change across scan angle can vary significantly between bands with the RSBs having smaller changes of ~2% and some TEBs having ~10% variation. Within a band, the RVS has both detector and HAM side dependencies that vary across scan. Errors in the RVS characterization will contribute to image banding and striping artifacts if their magnitudes are above the noise level of the detectors. The RVS was characterized pre-launch for both S-NPP and JPSS-1 VIIRS and a comparison of the RVS curves between these two sensors will be discussed.

Characterization of a Large Area ZnS(Ag) Detector for Gross Alpha and Beta Activity Measurements in Tap Water Plants

In this work we present the characterization of a large area $200~\hbox{mm} \times 200~\hbox{mm}$ EJ-444 scintillation detector to be used for monitoring gross alpha and beta activity in tap water plants. Specific tests were performed in order to determine the best setup to read-out the light from the detector side. The possibility to stack many detectors and get a compact device with total active area of the order of $1~\hbox{m}^2$ has been explored. Alpha/beta discrimination, efficiency and homogeneity tests were carried out with alpha and beta sources. Background from ambient radioactivity was measured as well. Alpha/beta real-time monitoring in drinking water is a goal of the EU project TAWARA_RTM.

Evaluation for Basic Image Qualities Dependence on the Position in XYZ Directions and Acquisition Parameters of the Cone Beam CT for Angiography System with Flat Panel Detector.

The purpose of this study was to investigate the effect of the position in XYZ directions and acquisition parameters on the basic image qualities of for cone beam computed tomography (CBCT) in an angiography system with flat panel detector. The resolution property (modulation transfer function: MTF) and the noise property (Wiener spectrum: WS) of CBCT images in X-Y plane were measured with different acquisition parameters (scan matrix number and projection number) and the effect of the position in XYZ directions. The MTFs with 1024×1024 matrix were higher than those of 512×512 matrix and decreased in the peripheral areas due to the reduction of projection number. The highest and the lowest MTFs were measured at the X-ray tube side and on the detector side of the position in X-Y plane, respectively. The WS-doubled projection number showed about 50% lesser noise level. There were differences in the Wiener spectra (WS) at the position in XYZ directions. We conclude that the resolution and the noise property of CBCT image in X-Y plane showed dependences on the position in XYZ directions and acquisition parameters of the CBCT.