Quantum random number generation based on phase reconstruction.

Quantum random number generator (QRNG) utilizes the intrinsic randomness of quantum systems to generate completely unpredictable and genuine random numbers, finding wide applications across many fields. QRNGs relying on the phase noise of a laser have attracted considerable attention due to their straightforward system architecture and high random number generation rates. However, traditional phase noise QRNGs suffer from a 50% loss of quantum entropy during the randomness extraction process. In this paper, we propose a phase-reconstruction quantum random number generation scheme, in which the phase noise of a laser is reconstructed by simultaneously measuring the orthogonal quadratures of the light field using balanced detectors. This enables direct discretization of uniform phase noise, and the min-entropy can achieve a value of 1. Furthermore, our approach exhibits inherent robustness against the classical phase fluctuations of the unbalanced interferometer, eliminating the need for active compensation. Finally, we conducted experimental validation using commercial optical hybrid and balanced detectors, achieving a random number generation rate of 1.96 Gbps at a sampling rate of 200 MSa/s.

Chip-Based Electronic System for Quantum Key Distribution.

Quantum Key Distribution (QKD) has garnered significant attention due to its unconditional security based on the fundamental principles of quantum mechanics. While QKD has been demonstrated by various groups and commercial QKD products are available, the development of a fully chip-based QKD system, aimed at reducing costs, size, and power consumption, remains a significant technological challenge. Most researchers focus on the optical aspects, leaving the integration of the electronic components largely unexplored. In this paper, we present the design of a fully integrated electrical control chip for QKD applications. The chip, fabricated using 28 nm CMOS technology, comprises five main modules: an ARM processor for digital signal processing, delay cells for timing synchronization, ADC for sampling analog signals from monitors, OPAMP for signal amplification, and DAC for generating the required voltage for phase or intensity modulators. According to the simulations, the minimum delay is 11ps, the open-loop gain of the operational amplifier is 86.2 dB, the sampling rate of the ADC reaches 50 MHz, and the DAC achieves a high rate of 100 MHz. To the best of our knowledge, this marks the first design and evaluation of a fully integrated driver chip for QKD, holding the potential to significantly enhance QKD system performance. Thus, we believe our work could inspire future investigations toward the development of more efficient and reliable QKD systems.

Indirect spectrum measurement via random phase modulation and detection in temporal domain.

Spectroscopy continues to provide possibilities for a deeper understanding of fundamental physical phenomena. Traditional spectral measurement method, dispersive Fourier transformation, is always limited by its realization condition (detection in the temporal far-field). Inspired by Fourier ghost imaging, we put forward an indirect spectrum measurement to overcome the limitation. The spectrum information is reconstructed via random phase modulation and near-field detection in the time domain. Since all operations are realized in the near-field region, the required length of dispersion fiber and optical loss are greatly reduced. Considering the application in spectroscopy, the length of required dispersion fiber, the spectrum resolution, the range of spectrum measurement and the requirement on bandwidth of photodetector are investigated.

A Review of Security Evaluation of Practical Quantum Key Distribution System.

Although the unconditional security of quantum key distribution (QKD) has been widely studied, the imperfections of the practical devices leave potential loopholes for Eve to spy the final key. Thus, how to evaluate the security of QKD with realistic devices is always an interesting and opening question. In this paper, we briefly review the development of quantum hacking and security evaluation technology for a practical decoy state BB84 QKD system. The security requirement and parameters in each module (source, encoder, decoder and detector) are discussed, and the relationship between quantum hacking and security parameter are also shown.

Hacking single-photon avalanche detectors in quantum key distribution via pulse illumination.

Quantum key distribution (QKD) has been proved to be information-theoretically secure in theory. Unfortunately, the imperfect devices in practice compromise its security. Thus, to improve the security property of practical QKD systems, a commonly used method is to patch the loopholes in the existing QKD systems. However, in this work, we show an adversary's capability of exploiting the imperfection of the patch itself to bypass the patch. Specifically, we experimentally demonstrate that, in the detector under test, the patch of photocurrent monitor against the detector blinding attack can be defeated by the pulse illumination attack proposed in this paper. We also analyze the secret key rate under the pulse illumination attack, which theoretically confirmed that Eve can conduct the attack to learn the secret key. This work indicates the importance of inspecting the security loopholes in a detection unit to further understand their impacts on a QKD system. The method of pulse illumination attack can be a general testing item in the security evaluation standard of QKD.

Field demonstration of time-bin reference-frame-independent quantum key distribution via an intracity free-space link.

Free-space quantum key distribution (QKD) based on mobile platforms, such as satellites, drones, and vehicles, is considered a promising way to overcome the rate-distance limit without a quantum repeater. Real-time reference frame calibration is required in most recent implemented polarization encoded QKD systems due to the relative motion between sender and receiver. Although active compensations can be used to calibrate the reference frame, doing so increases the complexity of the system and reduces the key rate. To overcome this problem, the reference-frame-independent (RFI) QKD was proposed in which fixed deviations of the reference frame between the two parties are tolerated automatically. In this Letter, we report the experimental implementation of a time-bin encoded RFI QKD in an urban environment through free space. The quantum bit error rate for key-distill is as low as 1% over a 2 km free-space link with a total equivalent loss of 31.5 dB. Our demonstration shows that a stable RFI QKD can be implemented in the free-space channel.

Detecting fast signals beyond bandwidth of detectors based on computational temporal ghost imaging.

Measurement of fast signal is getting more and more important in many fields. In this paper, we propose to detect a temporal signal based on the idea of computational ghost imaging (GI), which can greatly reduce requirements on bandwidth of detectors. In experiments, we implement retrieving of a temporal signal with time scale of 50ns using a detector of 1kHz bandwidth, which is much lower than the requirement on bandwidth of detector according to information theory. The performance of our technique are also investigated under different detection bandwidths.

Mutual information network-based support vector machine strategy identifies salivary biomarkers in gastric cancer.

PURPOSE: To determine the vital salivary transcriptomic biomarkers for the early detection of gastric cancer via comparing classification efficiency of multiple candidate genes. METHODS: We firstly identified 5 kinds of candidate genes related to gastric cancer, including differential pathway genes (DPGs) based on the attract method, hub genes in differential pathways based on mutual information network (MIN) analysis, differentially expressed genes (DEGs) identified by Significance Analysis of Microarrays (SAM), informative genes (DEGs in differential pathways), and key genes (hub DEGs). Then, the classification efficiency of these 5 kinds of candidate genes were assessed using support vector machines (SVM) model. The genes with the best classification efficiency were considered as salivary biomarkers in gastric cancer. RESULTS: Using the attract method, we screened 5 differential pathways in gastric cancer, in which there were 349 DPGs. Based on these DPGs, MIN with 345 genes and 1313 interactions was constructed, from which we obtained 26 hub genes by topological analysis. Meanwhile, we identified 374 DEGs in gastric cancer. Combining DEGs with DPGs and hub genes respectively, we selected 16 informative genes and 5 key genes. SVM analysis showed that the key genes presented the best classification efficiency with AUC=0.99, specificity=1.00, sensitivity=0.98 and MCC=0.95, which would be considered as salivary biomarkers in gastric cancer. CONCLUSIONS: This study successfully explored several salivary biomarkers for the non-invasive detection of gastric cancer with high specificity and sensitivity, which might contribute to the early detection and treatment of gastric cancer.

Insecurity of Detector-Device-Independent Quantum Key Distribution.

Detector-device-independent quantum key distribution (DDI-QKD) held the promise of being robust to detector side channels, a major security loophole in quantum key distribution (QKD) implementations. In contrast to what has been claimed, however, we demonstrate that the security of DDI-QKD is not based on postselected entanglement, and we introduce various eavesdropping strategies that show that DDI-QKD is in fact insecure against detector side-channel attacks as well as against other attacks that exploit devices' imperfections of the receiver. Our attacks are valid even when the QKD apparatuses are built by the legitimate users of the system themselves, and thus, free of malicious modifications, which is a key assumption in DDI-QKD.

Detwining in Mg alloy with a high density of twin boundaries.

To investigate the role of preexisting twin boundaries in magnesium alloys during the deformation process, a large number of {10-12} tensile twins were introduced by a radial compression at room temperature before hot compressive tests with both low and high strain rates. Unlike the stable twins in Cu-based alloys with low stacking fault energies, {10-12} twins in Mg alloy are extremely unstable or easy to detwin through {10-12}-{10-12} re-twinning. As a result, non-lenticular residual twins and twin traces with misorientation of 5°-7° were present, as confirmed by electron backscatter diffraction. The extreme instability of the twins during compression indicates that both twin and detwinning require extremely low resolved shear stresses under our experimental conditions.

Recent progress in quantum photonic chips for quantum communication and internet.

Recent years have witnessed significant progress in quantum communication and quantum internet with the emerging quantum photonic chips, whose characteristics of scalability, stability, and low cost, flourish and open up new possibilities in miniaturized footprints. Here, we provide an overview of the advances in quantum photonic chips for quantum communication, beginning with a summary of the prevalent photonic integrated fabrication platforms and key components for integrated quantum communication systems. We then discuss a range of quantum communication applications, such as quantum key distribution and quantum teleportation. Finally, the review culminates with a perspective on challenges towards high-performance chip-based quantum communication, as well as a glimpse into future opportunities for integrated quantum networks.

Quantum key distribution based on phase encoding in long-distance communication fiber.

A robust two-way quantum key distribution system based on phase encoding is demonstrated in 50 km and 100 km commercial communication fiber. The system can automatically compensate for birefringence effects and remain stable over 23 h. A low quantum bit error rate and high visibility are obtained. Furthermore, the storage fiber is unnecessary and train of pulses is only needed in the test with 100 km fiber.

Security evaluation of quantum key distribution with weak basis-choice flaws.

Quantum key distribution (QKD) can share an unconditional secure key between two remote parties, but the deviation between theory and practice will break the security of the generated key. In this paper, we evaluate the security of QKD with weak basis-choice flaws, in which the random bits used by Alice and Bob are weakly controlled by Eve. Based on the definition of Li et al. (Sci Rep 5:16200, 2015) and GLLP's analysis, we obtain a tight and analytical bound to estimate the phase error and key rate for both the single photon source and the weak coherent source. Our approach largely increases the key rate from that of the original approach. Finally, we investigate and confirm the security of BB84-QKD with a practical commercial devices.

Retraction: Hacking on decoy-state quantum key distribution system with partial phase randomization.

This corrects the article DOI: 10.1038/srep04759.

Propylthiouracil-Induced Vasculitis With Alveolar Hemorrhage Confirmed by Clinical, Laboratory, Computed Tomography, and Bronchoscopy Findings: A Case Report and Literature Review.

INTRODUCTION: Propylthiouracil (PTU) is commonly used to treat hyperthyroidism and can induce antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis. Although this is a rare side effect, ANCA-associated vasculitis can progress to severe disease if its diagnosis and treatment are delayed, leading to a poor prognosis. CASE PRESENTATION: A 43-year-old woman with Graves' disease developed pulmonary vasculitis and diffuse alveolar hemorrhage (DAH) associated with ANCA against myeloperoxidase and proteinase-3 that was confirmed by computed tomography (CT) and bronchoscopy and treated with PTU. The symptoms and signs of alveolar hemorrhage were rapidly resolved after PTU withdrawal and treatment with corticosteroids. After 6 months of follow-up, the patient maintained complete ANCA-negative clinical remission status, as confirmed by normal CT and bronchoscopy findings. To our knowledge, this is the first documented case of bronchoscopic comparison of PTU-induced DAH before and after steroid treatment. CONCLUSIONS: Patients treated with PTU should be closely monitored and followed up, even if the drug has been used for several years. When patients develop progressive dyspnea with alveolar opacities on chest imaging that cannot be explained otherwise, alveolar hemorrhage should be an important differential diagnosis while investigating the case. Early diagnosis and prompt discontinuation of the PTU treatment are essential for improving patient outcomes.

Hacking on decoy-state quantum key distribution system with partial phase randomization.

Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a hybrid measurement attack, with only linear optics, homodyne detection, and single photon detection, to the widely used vacuum + weak decoy state QKD system when the phase of source is partially randomized. Our analysis shows that, in some parameter regimes, the proposed attack would result in an entanglement breaking channel but still be able to trick the legitimate users to believe they have transmitted secure keys. That is, the eavesdropper is able to steal all the key information without discovered by the users. Thus, our proposal reveals that partial phase randomization is not sufficient to guarantee the security of phase-encoding QKD systems with weak coherent states.