Free-space measurement-device-independent quantum-key-distribution protocol using decoy states with orbital angular momentum

In this paper, we propose a measurement-device-independent quantum-key-distribution（MDI-QKD） protocol using orbital angular momentum（OAM） in free space links, named the OAM-MDI-QKD protocol. In the proposed protocol,the OAM states of photons, instead of polarization states, are used as the information carriers to avoid the reference frame alignment, the decoy-state is adopted to overcome the security loophole caused by the weak coherent pulse source, and the high efficient OAM-sorter is adopted as the measurement tool for Charlie to obtain the output OAM state. Here, Charlie may be an untrusted third party. The results show that the authorized users, Alice and Bob, could distill a secret key with Charlie＇s successful measurements, and the key generation performance is slightly better than that of the polarization-based MDI-QKD protocol in the two-dimensional OAM cases. Simultaneously, Alice and Bob can reduce the number of flipping the bits in the secure key distillation. It is indicated that a higher key generation rate performance could be obtained by a high dimensional OAM-MDI-QKD protocol because of the unlimited degree of freedom on OAM states. Moreover,the results show that the key generation rate and the transmission distance will decrease as the growth of the strength of atmospheric turbulence（AT） and the link attenuation. In addition, the decoy states used in the proposed protocol can get a considerable good performance without the need for an ideal source.

Security of a practical semi-device-independent quantum key distribution protocol against collective attacks

Similar to device-independent quantum key distribution （DI-QKD）, semi-device-independent quantum key distribu- tion （SDI-QKD） provides secure key distribution without any assumptions about the internal workings of the QKD devices. The only assumption is that the dimension of the Hilbert space is bounded. But SDI-QKD can be implemented in a one- way prepare-and-measure configuration without entanglement compared with DI-QKD. We propose a practical SDI-QKD protocol with four preparation states and three measurement bases by considering the maximal violation of dimension witnesses and specific processes of a QKD protocol. Moreover, we prove the security of the SDI-QKD protocol against collective attacks based on the min-entropy and dimension witnesses. We also show a comparison of the secret key rate between the SDI-QKD protocol and the standard QKD.

Measurement Device Independent Quantum Key Distribution Based on Orbital Angular Momentum under Parametric Light Source

On the one hand,existing measurement device independent quantum key distribution(MDI-QKD)protocols have usually adopted single photon source(SPS)and weak coherent photon(WCP),however,these protocols have suffered from multi-photon problem brought from photon splitter number attacks.On the other hand,the orbital angular momentum(OAM)-MDI-QKD protocol does not need to compare and adjust the reference frame,solving the dependency of the base in the MDI-QKD protocol.Given that,we propose the OAM-MDI-QKD protocol based on the parametric light sources which mainly include single-photon-added-coherent(SPACS)and heralded single-photon sources(HSPS).Due to the stability of OAM and the participation of parametric light sources,the performance of MDI-QKD protocol gradually approaches the ideal situation.Numerical simulation shows that compared with WCP scheme,HSPS and SPACS schemes have increased the maximum secure transmission distance by 30 km and 40 km respectively.

Measurement-device-independent quantum cryptographic conferencing with an untrusted source

Measurement-device-independent quantum cryptographic conferencing（MDI-QCC） protocol puts MDI quantum key distribution（MDI-QKD） forwards to multi-party applications, and suggests a significant framework for practical multi-party quantum communication. In order to mitigate the experimental complexity of MDI-QCC and remove the key assumption（the sources are trusted） in MDI-QCC, we extend the framework of MDI-QKD with an untrusted source to MDI-QCC and give the rigorous security analysis of MDI-QCC with an untrusted source. What is more, in the security analysis we clearly provide a rigorous analytical method for parameters＇ estimation, which with simple modifications can be applied to not only MDI-QKD with an untrusted source but also arbitrary multi-party communication protocol with an untrusted source. The simulation results show that at reasonable distances the asymptotic key rates for the two cases（with trusted and untrusted sources） almost overlap, which indicates the feasibility of our protocol.

Performance analysis of continuous-variable measurement-device-independent quantum key distribution under diverse weather conditions

The effects of weather conditions are ubiquitous in practical wireless quantum communication links.Here in this work,the performances of atmospheric continuous-variable measurement-device-independent quantum key distribution(CV-MDI-QKD)under diverse weather conditions are analyzed quantitatively.According to the Mie scattering theory and atmospheric CV-MDI-QKD model,we numerically simulate the relationship between performance of CV-MDI-QKD and the rainy and foggy conditions,aiming to get close to the actual combat environment in the future.The results show that both rain and fog will degrade the performance of the CV-MDI-QKD protocol.Under the rainy condition,the larger the raindrop diameter,the more obvious the extinction effect is and the lower the secret key rate accordingly.In addition,we find that the secret key rate decreases with the increase of spot deflection distance and the fluctuation of deflection.Under the foggy condition,the results illustrate that the transmittance decreases with the increase of droplet radius or deflection distance,which eventually yields the decrease in the secret key rate.Besides,in both weather conditions,the increase of transmission distance also leads the secret key rate to deteriorate.Our work can provide a foundation for evaluating the performance evaluation and successfully implementing the atmospheric CV-MDI-QKD in the future field operation environment under different weather conditions.

Hong–Ou–Mandel interference with two independent weak coherent states

Recently, the Hong-Ou-Mandel （HOM） interference between two independent weak coherent pulses （WCPs） has been paid much attention due to the measurement-device-independent （MDI） quantum key distribution （QKD）. Using classical wave theory, articles reported before show that the visibility of this kind of HOM-type interference is 〈 50%. In this work, we analyze this kind of interference using quantum optics, which reveals more details compared to the wave theory. Analyses confirm the maximum visibility of 50%. And we conclude that the maximum visibility of 50% comes from the two single-photon states in WCPs, without considering the noise. In the experiment, we successfully approach the visibility of 50% by using WCPs splitting from the single pico-second laser source and phase scanning. Since this kind of HOM interference is immune to slow phase fluctuations, both the realized and proposed experiment designs can provide stable ways of high-resolution optical distance detection.

Research on Anti-collision Capability and Safety Supervision Measures of the Nanjing Yangtze River Bridge

With the vigorous development of inland river shipping economy,the trend of large ships passing Nanjing Yangtze River Bridge is obvious.The standard formula of ship collision force is selected by comparing the empirical calculation formulas.Four representative ship types are selected for calculation and analyzing of collision force.It is concluded that the anti-collision ability of the Nanjing Yangtze River Bridge does not meet the requirement of large ship collision force when the speed is more than 8-knots.From the perspective of active collision avoidance,this paper puts forward the navigation safety supervision countermeasures.A conceptual model of guided pulley anti-collision device is designed from the perspective of passive anti-collision.The research results provide references for safety supervision and anti-collision measures for the bridge.

Measurement-device-independent quantum communication without encryption

Security in communication is vital in modern life. At present, security is realized by an encryption process in cryptography. It is unbelievable if a secure communication is achievable without encryption. In quantum cryptography, there is a unique form of quantum communication, quantum secure direct communication, where secret information is transmitted directly over a quantum channel. Quantum secure direct communication is drastically distinct from our conventional concept of secure communication, because it does not require key distribution, key storage and ciphertext transmission, and eliminates the encryption procedure completely. Hence it avoids in principle all the security loopholes associated with key and ciphertext in traditional secure communications. For practical implementation, defects always exist in real devices and it may downgrade the security. Among the various device imperfections, those with the measurement devices are the most prominent and serious ones. Here we report a measurementdevice-independent quantum secure direct communication protocol using Einstein-Podolsky-Rosen pairs. This protocol eradicates the security vulnerabilities associated with the measurement device,and greatly enhances the practical security of quantum secure direct communication. In addition to the security advantage, this protocol has an extended communication distance, and a high communication capacity.

Realization of a source-device-independent quantum random number generator secured by nonlocal dispersion cancellation

Quantum random number generators(QRNGs)can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics,which play important roles in many applications.However,the true randomness acquisition could be subjected to attacks from untrusted devices involved or their deviations from the theoretical modeling in real-life implementation.We propose and experimentally demonstrate a source-device-independent QRNG,which enables one to access true random bits with an untrusted source device.The random bits are generated by measuring the arrival time of either photon of the time–energy entangled photon pairs produced from spontaneous parametric downconversion,where the entanglement is testified through the observation of nonlocal dispersion cancellation.In experiment,we extract a generation rate of 4 Mbps by a modified entropic uncertainty relation,which can be improved to gigabits per second by using advanced single-photon detectors.Our approach provides a promising candidate for QRNGs with no characterization or error-prone source devices in practice.

Loss-tolerant measurement device independent quantum key distribution with reference frame misalignment

Reference frame independent and measurement device independent quantum key distribution(RFI-MDI-QKD)has the advantages of being immune to detector side loopholes and misalignment of the reference frame.However,several former related research works are based on the unrealistic assumption of perfect source preparation.In this paper,we merge a loss-tolerant method into RFI-MDI-QKD to consider source flaws into key rate estimation and compare it with quantum coin method.Based on a reliable experimental scheme,the joint influence of both source flaws and reference frame misalignment is discussed with consideration of the finite-key effect.The results show that the loss-tolerant RFI-MDI-QKD protocol can reach longer key rate performance while considering the existence of source flaws in a real-world implementation.

Device-independent quantum secure direct communication against collective attacks

"Device-independent"not only represents a relaxation of the security assumptions about the internal working of the quantum devices,but also can enhance the security of the quantum communication.In the paper,we put forward the first device-independent quantum secure direct communication(DIQSDC)protocol and analyze its security and communication efficiency against collective attacks.Under practical noisy quantum channel condition,the photon transmission loss and photon state decoherence would reduce DI-QSDC’s communication quality and threaten its absolute security.For solving the photon transmission loss and decoherence problems,we adopt noiseless linear amplification(NLA)protocol and entanglement purification protocol(EPP)to modify the DI-QSDC protocol.With the help of the NLA and EPP,we can guarantee DI-QSDC’s absolute security and effectively improve its communication quality.

Measurement-device-independent quantum key distribution with hyper-encoding

Measurement device-independent quantum key distribution(MDI-QKD) protocols are immune to all possible attacks on the photon detectors during quantum communication, but their key generation rates are low compared with those of other QKD schemes.Increasing each individual photon’s channel capacity is an efficient way to increase the key generation rate, and high-dimensional(HD) encoding is a powerful tool for increasing the channel capacity of photons. In this paper, we propose an HD MDI-QKD protocol with qudits hyper-encoded in spatial mode and polarization degrees of freedom(DOFs). In the proposed protocol, keys can be generated using the spatial mode and polarization DOFs simultaneously. The proposed protocol is unconditionally secure,even for weak coherent pulses with decoy states. The proposed MDI-QKD protocol may be useful for future quantum secure communication applications.

Tomographic Approach in Reference-Frame-Independent Measurement-Device-Independent Quantum Key Distribution

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.

基于BP神经网络的测量设备无关协议参数预测

针对传统参数优化方法计算开销大,不能满足实时性要求高、计算量大等应用场景的问题,结合当今主流的机器学习方法,提出了一种改进的基于BP神经网络的参数优化方法,利用本地搜索算法的数据训练网络并对参数进行预测,替代传统的查找算法,从而获得更好的实时性和更低的计算复杂度,随后与基于随机森林和XGBoost的方法进行了比较。仿真结果表明,BP神经网络预测所得各参数的均方误差数量级为10^(-6)或更小,由该参数计算所得密钥生成率与最优密钥生成率比值的均值为0.998 8,且该应用中BP神经网络相对随机森林和XGBoost具有更好的预测性能。

Research on measurement-device-independent quantum key distribution based on an air-water channel

A measurement-device-independent quantum key distribution(MDI-QKD) method with an air-water channel is researched. In this method, the underwater vehicle and satellite are the legitimate parties, and the third party is at the airwater interface in order to simplify the unilateral quantum channel to water or air. Considering the condition that both unilateral transmission distance and transmission loss coefficient are unequal, a perfect model of the asymmetric channel is built. The influence of asymmetric channel on system loss tolerance and secure transmission distance is analyzed. The simulation results show that with the increase of the channel's asymmetric degree, the system loss tolerance will descend, one transmission distance will be reduced while the other will be increased. When the asymmetric coefficient of channel is between 0.068 and 0.171, MDI-QKD can satisfy the demand of QKD with an air-water channel, namely the underwater transmission distance and atmospheric transmission distance are not less than 60 m and 12 km, respectively.

人工智能医疗监管与治理创新:突破现行规范框架的思考

随着以深度学习和生成式人工智能为代表的人工智能应用的爆发式增长,人工智能技术已经进入医疗健康各个领域,包括临床诊疗、医院管理、科学研究、教育培训和健康管理等,为患者带来高效优质服务的同时,也涌现出一系列治理制度需要解决和探索的问题,尤其是在人工智能医疗产品监管方面。目前,各国监管机构大多以风险等级方式进行人工智能医疗产品监管,基本将人工智能产品定位为“辅助”性质,即需要医师签字确认自动判读结果并承担法律责任。世界卫生组织先后发布两项人工智能指南,旨在对卫生健康领域人工智能技术的开发、提供和部署提供指导框架,并在肺结核这类特殊疾病诊断上提出突破性“独立使用”的建议,美国监管机构也提出“软件预认证”的突破性思路以缩短审批流程并创新监管方式。尝试从技术治理制度创新的角度出发,借鉴国际相关经验,结合中国技术发展与实践情况,提出针对特定应用场景、风险程度较低人工智能产品逐步开放“独立”应用,以及对于尚未纳入监管的风险较高人工智能医疗产品进行“机构预认证”的治理思路,为制度创新提供一些可操作的路径。

一种独立驱动烟条切割装置安全调试方法研究

目前,国产超高速卷接机组上的烟支切割装置,采用的是刀盘和喇叭嘴独立驱动的技术。该装置取消了机械传动,刀盘和喇叭嘴改为独立的伺服电动机驱动。该装置中,高速旋转刀盘上均匀分布的刀片需依次穿过喇叭嘴的缝隙,从而实现对喇叭嘴中高速通过的烟条进行切割,这要求驱动喇叭嘴和刀盘的两个电动机必须同步协调,确保刀片与喇叭嘴不发生撞刀。按安全要求,设备防护罩处于关闭状态时,伺服电动机才能启动,但在调试阶段,需要打开防护罩,对独立驱动烟支切割装置进行调试。通过对刀盘电动机、喇叭嘴电动机划分自由区和干涉区,分析两个电动机同步条件;探索伺服电动机Safely-Limited Speed(SLS)功能,在电动机速度低于设定值时,允许电动机在防护罩打开的情况下,进行同步、调试操作。

测量设备无关量子密钥分发中的改进型诱骗态方法

测量设备无关量子密钥分发协议作为量子网络的候选组件之一,消除了探测端的所有漏洞,提升了系统安全性。目前的测量设备无关量子密钥分发协议采用非理想单光子源,并引入了诱骗态方法来提高密钥率。最近,一种整合在诱骗态方法中的数据后处理方法双扫描法在统计波动方面表现出色。使用诱骗态方法估算单光子对成分时,引入双扫描法能获得更高的密钥率。然而,双扫描法需要耗时的优化过程。在此,文章提出了一种新颖的改进型诱骗态方法,以实现比原始诱骗态方法更好的性能,同时避免了类似双扫描法优化时间的出现。在文章所有的实验参数值模拟中,改进型诱骗态方法均比原始诱骗态方法的密钥率更高;相较于双扫描法,文章所提方法具有速度快、兼容性好的优点。

基于深度学习的第三类独立医用软件产品现状分析和展望

目的:根据人工智能医疗器械中的第三类深度学习独立软件及其企业的相关情况,分析二者的特征和内在原因,为产业发展提供参考。方法:根据国家药品监督管理局网站和国家企业信用信息公示系统网站的公开信息,整理第三类深度学习独立软件及企业信息,并做描述性统计分析。结果:2020年以来,我国有53项第三类深度学习独立软件通过了注册审批,审评数量逐年增加,主要集中在肺和心脏等部位。这些产品分别属于26家企业,在成立时间和地域分布上呈现一定的集中趋势。结论:人工智能医疗器械的健康发展,需持续以临床应用为导向,加强配套政策支持,重视技术和人才的创新作用。

防喷器组板式起吊装置有限元结构强度分析及网格无关性探究

针对某防喷器组板式起吊装置进行有限元结构强度分析,确定应力危险区域,并据此针对有限元结构强度分析过程中网格无关性展开探究,论述有限元结构强度分析中网格无关性即不同网格尺寸将直接影响分析过程中的计算资源、时间成本及最终分析结果的有效性,为有限元结构强度分析中网格无关性提供建议。