Measurement-device-independent one-step quantum secure direct communication

The one-step quantum secure direct communication(QSDC)(Sci.Bull.67,367(2022))can effectively simplify QSDC’s operation and reduce message loss.For enhancing its security under practical experimental condition,we propose two measurement-device-independent(MDI)one-step QSDC protocols,which can resist all possible attacks from imperfect measurement devices.In both protocols,the communication parties prepare identical polarization-spatial-mode two-photon hyperentangled states and construct the hyperentanglement channel by hyperentanglement swapping.The first MDI one-step QSDC protocol adopts the nonlinear-optical complete hyperentanglement Bell state measurement(HBSM)to construct the hyperentanglement channel,while the second protocol adopts the linear-optical partial HBSM.Then,the parties encode the photons in the polarization degree of freedom and send them to the third party for the hyperentanglementassisted complete polarization Bell state measurement.Both protocols are unconditionally secure in theory.The simulation results show the MDI one-step QSDC protocol with complete HBSM attains the maximal communication distance of about354 km.Our MDI one-step QSDC protocols may have potential applications in the future quantum secure communication field.

Noise analysis and measurement of time delay and integration charge coupled device

Time delay and integration （TDI） charge coupled device （CCD） noise sets a fundamental limit on image sensor performance, especially under low illumination in remote sensing applications. After introducing the complete sources of CCD noise, we study the effects of TDI operation mode on noise, and the relationship between different types of noise and number of the TDI stage. Then we propose a new technique to identify and measure sources of TDI CCD noise employing mathematical statistics theory, where theoretical analysis shows that noise estimated formulation converges well. Finally, we establish a testing platform to carry out experiments, and a standard TDI CCD is calibrated by using the proposed method. The experimental results show that the noise analysis and measurement methods presented in this paper are useful for modeling TDI CCDs.

H-infinity measurement-feedback control for discrete-time systems with a single measurement delay

H-infinity control problem for linear discrete-time systems with instantaneous and delayed measurements is studied. A necessary and sufficient condition for the existence of the H-infinity controller is derived by applying reorganized innovation analysis approach in Krein space. The measurement-feedback controller is designed by performing two Riccati equations. The presented approach does not require the state augmentation.

Stochastic bounded consensus tracking of leader-follower multi-agent systems with measurement noises based on sampled data with general sampling delay

In this paper we provide a unified framework for consensus tracking of leader-follower multi-agent systems with measurement noises based on sampled data with a general sampling delay. First, a stochastic bounded consensus tracking protocol based on sampled data with a general sampling delay is presented by employing the delay decomposition technique. Then, necessary and sufficient conditions are derived for guaranteeing leader-follower multi-agent systems with measurement noises and a time-varying reference state to achieve mean square bounded consensus tracking. The obtained results cover no sampling delay, a small sampling delay and a large sampling delay as three special cases. Last, simulations are provided to demonstrate the effectiveness of the theoretical results.

One-step quantum dialogue

Quantum dialogue(QD)enables two communication parties to directly exchange secret messages simultaneously.In conventional QD protocols,photons need to transmit in the quantum channel for two rounds.In this paper,we propose a one-step QD protocol based on the hyperentanglement.With the help of the non-local hyperentanglement-assisted Bell state measurement(BSM),the photons only need to transmit in the quantum channel once.We prove that our one-step QD protocol is secure in theory and numerically simulate its secret message capacity under practical experimental condition.Compared with previous QD protocols,the one-step QD protocol can effectively simplify the experiment operations and reduce the message loss caused by the photon transmission loss.Meanwhile,the non-local hyperentanglement-assisted BSM has a success probability of 100%and is feasible with linear optical elements.Moreover,combined with the hyperentanglement heralded amplification and purification,our protocol is possible to realize long-distance one-step QD.

MEASUREMENT OF AMPLITUDE AND DELAY OF STIMULUS FREQUENCY OTOACOUSTIC EMISSIONS

Although stimulus frequency otoacoustic emissions (SFOAEs) have been used as a non-invasive measure of cochlear mechanics, clinical and experimental application of SFOAEs has been limited by difficulties in accurately deriving quantitative information from sound pressure measured in the ear canal. In this study, a novel signal processing method for multicomponent analysis (MCA) was used to measure the amplitude and delay of the SFOAE. This report shows the delay-frequency distribution of the SFOAE measured from the human ear. A low level acoustical suppressor near the probe tone significantly suppressed the SFOAE, strongly indicating that the SFOAE was generated at characteristic frequency locations. Information derived from this method may reveal more details of cochlear mechanics in the human ear.

Impact of photoneutrons on reactivity measurements for TMSR-SF1

The solid-fueled thorium molten salt reactor(TMSR-SF1) is a 10 MW_(th) test reactor design to be deployed in 5-10 years by the TMSR group.Its design combines coated particle fuel and molten FLiBe coolant for great intrinsic safety features and economic advantages.Due to a large amount of beryllium in the coolant salt,photoneutrons are produced by(y,n) reaction,hence the increasing fraction of effective delayed neutrons in the core by the photoneutrons originating from the long-lived fission products.Some of the delayed photoneutron groups are of long lifetime,so a direct effect is resulted in the transient process and reactivity measurement.To study the impact of photoneutrons for TMSR-SF1,the effective photoneutron fraction is estimated using k-ratio method and performed by the Monte Carlo code(MCNP5) with ENDF/B-Ⅶ cross sections.Based on the coupled neutronphoton point kinetics equations,influence of the photoneutrons is analyzed.The results show that the impact of photoneutrons is not negligible in reactivity measurement.Without considering photoneutrons in on-line reactivity measurement based on inverse point kinetics can result in overestimation of the positive reactivity and underestimation of the negative reactivity.The photoneutrons also lead to more waiting time for the doubling time measurement.Since the photoneutron precursors take extremely long time to achieve equilibrium,a "steady" power operation may not directly imply a "real" criticality.

Measuring Absolute Delay of RNSS Signal Channel Using Digital Envelope Detection

The absolute delay caused by equipment of radio navigation satellite service (RNSS) signal channel must be calibrated in the application of positioning. The measurement accuracy of absolute delay will affect the positioning precision of RNSS user. An absolute delay measurement technique using digital envelope detection was developed for RNSS signal transmission channel. The RNSS transmission signal of navigation satellite and the one pulse per second (1PPS)generated by satellite time keeping system were sampled synchronously. With sampling data of 1PPS,the reference point of the absolute delay can be decided at first,and then sampling data of RNSS transmission signal were truncated. The truncated data were processed using digital envelop detection algorithm to search the phase converting points of RNSS signal. Finally,the absolute delay of RNSS signal transmitting channel was calculated. Uncertainty of measurement with proposed technique is lower than 0. 2 ns as the sampling frequency is 10 GHz.

FPGA-based High-precision Measurement Algorithm for the Ultrasonic Echo Time of Flight

Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the requirements for the measurement of echo time of flight put forward by the ultrasonic flow measurement are analyzed. A new high-precision time interval measurement algorithm is presented, which combines the pulse counting method with the phase delay interpolation. The pulse counting method is used to ensure a large dynamic measuring range, and a double-edge triggering counter is designed to improve the accuracy and reduce the counting quantization error. The phase delay interpolation is used to reduce the quantization error of pulse counting for further improving the time measurement resolution. Test data show that the systexn for the measurement of the ultrasonic echo time of flight based on this algorithm and implemented on an Field Programmable Gate Army（FleA） needs a relatively short time for measurement, and has a measurement error of less than 105 ps.

A new high-precision gravity solid tidal model for Precision Gravity Measurement Facility

It is significant for establishing gravity datum to construct precise gravity solid tidal model,A simple method with relatively low performance is to interpolate tidal parameters from the global gravity solid tide models.A competitive approach is to determine local gravity solid tidal model by harmonic analysis using long-time serial gravity observations.In this paper a new high-precision gravity solid tidal model for Precision Gravity Measurement Facility is estimated from two co-site gravimeters in the cave laboratory using modern international standard data processing techniques,whose accuracy is evaluated further by comparing with previous publications.The results show that:(1)the determined gravity solid tidal models from two co-site gravimeters are in good agreement with each other,of which the maximum differences for amplitude factors and phase delays don’t exceed 0.01700%and 2.50990°,respectively.(2)the performance of the obtained gravity solid tidal model is 0.00411 for amplitude factors and 0.24120°for phase delays,which is a little better than that of previous publications using superconducting gravity data from Wuhan station.(3)our results and methods are corrective and effective.(4)our model is tiny different from that provided by Wuhan station,which implies that it is necessary to construct a gravity solid tidal model for Precision Gravity Measurement Facility,rather than just adopting existing models at Wuhan station.Our results are helpful in realizing the goal of Precision Gravity Measurement Facility.

STABILITY CRITERIA IN TERMS OF TWO MEASURES FOR DELAY DIFFERENTIAL EQUATIONS

By using the variational Liapunov method, stability properties in terms of two measures for delay differential equations are discussed. In the case that the unperturbed systems are ordinary differential systems, employing auxiliary measure h*(t, x), criteria on nonuniform and uniform stability in terms of two measures for delay differential equations are established.

Frequency dependence on polarization switching measurement in ferroelectric capacitors

Ferroelectric hysteresis loop measurement under high driving frequency generally faces great challenges.Parasitic factors in testing circuits such as leakage current and RC delay could result in abnormal hysteresis loops with erroneous rem-nant polarization(P_(r))and coercive field(E_(c)).In this study,positive-up-negative-down(PUND)measurement under a wide fre-quency range was performed on a 10-nm thick Hf_(0.5)Zr_(0.5)O_(2) ferroelectric film.Detailed analysis on the leakage current and RC delay was conducted as the polarization switching occurs in the FE capacitor.After considering the time lag caused by RC delay,reasonable calibration of current response over the voltage pulse stimulus was employed in the integral of polarization current over time.In such a method,rational P-V loops measured at high frequencies(>1 MHz)was successfully achieved.This work provides a comprehensive understanding on the effect of parasitic factors on the polarization switching behavior of FE films.

Measurements and analysis at 400MHz and 2600MHz in corridor radio channel

A propagation measurement campaign was performed at the 10 th floor corridor of Xingjian Building,Shanghai University,China.The channel was sounded by pseudo noise( PN) sequence at carrier frequencies of 400-and 2600-MHz respectively.In order to obtain large scale and small scale propagation characteristics in the corridor,the receiver was moved along the corridor every 1.02 meter to record the impulse response.More than 280,000 impulse responses were recorded in the campaign.This work first describes the principle of the measurement,and then how the recorded raw data are processed.The results show that path loss exponent is related to frequency.The relationship between the root-mean squared( RMS) delay spread and the T-R separation distance is analyzed.The RMS delay spread and the mean excess delay spread against path loss are also given,which explain why the 2600 MHz RMS delay spread is larger than that of 400 MHz.

Research of Impact of Geografical Latitute and Residual Ionospheric Noises on Informativeness of Measuring of Zenith Wet Delay of GPS Signals

It is noted that necessity of further increase of accuracy of GPS positioning systems requires de-velopment of more perfect methods to compensate information losses occurred due to residual ionospheric delay by using optimization procedures. According to the conditions of formulated optimization task, the signal/noise ratio in measurements of zenith wet delay depends on the second order ionospheric errors, geographic latitude and day of year. At the same time if we assume that the number of measurements at the fixed geographic site is proportional to geographic latitude and if we accept existence of only two antiphase scenarios for variation of residual ionospheric delay on latitude normed by their specific constant, there should be optimum functional dependence of precipitated water on latitude upon which the quantity of measuring information reaches the maximum. The mathematical grounding of solution of formulated optimization task is given.

Precise Optical Fiber Length Measurement System Based on Fresnel Reflection

In this study, a precise optical fiber length measurement system is proposed. The measurement technique is based on the measurement of relative Fresnel reflected light intensity in a test fiber. Time delayed optical reflected pulses are obtained from a single nanosecond pulse injected at the input due to the difference in lengths of the reference and test fibers. The lengths of the different optical fibers have been measured with this technique with high resolution and fast response time. The measured results show that, the proposed technique has a comparable performance with the well-known length measurement systems.

Time-resolution enhanced multi-path OTD measurement using an adaptive filter based incoherent OFDR

High accuracy and time resolution optical transfer delay(OTD)measurement is highly desired in many multi-path applications,such as optical true-time-delay-based array systems and distributed optical sensors.However,the time resolution is usually limited by the frequency range of the probe signal in frequency-multiplexed OTD measurement techniques.Here,we proposed a time-resolution enhanced OTD measurement method based on incoherent optical frequency domain reflectometry(I-OFDR),where an adaptive filter is designed to suppress the spectral leakage from other paths to break the resolution limitation.A weighted least square(WLS)cost function is first established,and then an iteration approach is used to minimize the cost function.Finally,the appropriate filter parameter is obtained according to the convergence results.In a proof-of-concept experiment,the time-domain response of two optical links with a length difference of 900 ps is successfully estimated by applying a probe signal with a bandwidth of 400 MHz.The time resolution is improved by 2.78times compared to the theoretical resolution limit of the inverse discrete Fourier transform(iDFT)algorithm.In addition,the OTD measurement error is below±0.8 ps.The proposed algorithm provides a novel way to improve the measurement resolution without applying a probe signal with a large bandwidth,avoiding measurement errors induced by the dispersion effect.

Robust state estimation for uncertain linear discrete systems with d-step measurement delay and deterministic input signals

In this study,the state estimation problems for linear discrete systems with uncertain parameters,deterministic input signals and d-step measurement delay are investigated.A robust state estimator with a similar iterative form and comparable computational complexity to the Kalman filter is derived based on the state augmentation method and the sensitivity penalisation of the innovation process.It is discussed that the steady-state properties such as boundedness and convergence of the robust state estimator under the assumptions that the system parameters are time invariant.Numerical simulation results show that compared with the Kalman filter,the obtained state estimator is more robust to modelling errors and has nice estimation accuracy.

OPTIMAL DISTRIBUTED FUSION ALGORITHM WITH ONE-STEP OUT-OF-SEQUENCE ESTIMATES

The transmission modes of multi-hop and broadcasting for Wireless Sensor Networks(WSN)often make random and unknown transmission delays appear,so multisensor data fusion based ondelayed systems attracts intense attention from lots of researchers.The existing achievements for thedelayed fusion all focus on Out-Of-Sequence Measurements(OOSM)problem which has many dis-advantages such as high communication cost,low computational efficiency,huge computational com-plexity and storage requirement,bad real-time performance and so on.In order to overcome theseproblems occurred in the OOSM fusion,the Out-Of-Sequence Estimates(OOSE)are considered tosolve the delayed fusion for the first time.Different from OOSM which belongs to the centralized fusion,the OOSE scheme transmits local estimates from local sensors to the central processor and is thus thedistributed fusion;thereby,the OOSE fusion can not only avoid the problems suffered in the OOSMfusion but also make the design of fusion algorithm highly simple and easy.Accordingly,a novel optimallinear recursive prediction weighted fusion method is proposed for one-step OOSE problem in this letter.As a tradeoff,its fusion accuracy is slightly lower than that of the OOSM method because the currentOOSM fusion is a smooth estimate and OOSE gets a prediction estimate.But,the smooth result of theOOSE problem also has good fusion accuracy.Performance analysis and computer simulation show thatthe total performance of the proposed one-step OOSE fusion algorithm is better than the current one-step OOSM fusion in the practical tracking systems.

Particle filter for nonlinear systems with multi-sensor asynchronous random delays

This paper is concerned with the recursive filtering problem for a class of discrete-time nonlinear stochastic systems in the presence of multi-sensor measurement delay. The delay occurs in a multi-step and asynchronous manner, and the delay probability of each sensor is assumed to be known or unknown. Firstly, a new model is constructed to describe the measurement process, based on which a new particle filter is developed with the ability to fuse multi-sensor information in the case of known delay probability.In addition, an online delay probability estimation module is introduced in the particle filtering framework, which leads to another new filter that can be implemented without the prior knowledge of delay probability. More importantly, since there is no complex iterative operation, the resulting filter can be implemented recursively and is suitable for many real-time applications. Simulation results show the effectiveness of the proposed filters.

HYBRID FILTER WITH PREDICT-ESTIMATOR AND COMPENSATOR FOR THE LINEAR TIME INVARIANT DELAYED SYSTEM

This paper investigates the problem of real-time estimation for one kind of linear time invariant systems which subject to limited communication capacity. The communication limitations include signal transmission delay, the out-of-sequence measurements and data packet dropout, which appear typically in a network environment. The kernel of filter design is equally to formularize the traditional Kalman filter as one linear weighted summation which is composed of the initial state estimate and all sequential sampled measurements. For it can adapt aforementioned information limitations, the linear weighted summation is then decomposed into two stages. One is a predict-estimator composed by all reached measurements, another is one compensator constructed by those time-delayed data. In the network environment, there are obvious differences between the new hybrid filter and those existing delayed Kalman filters. For example, the novel filter can be optimal in the sense of linear minimum mean square error as soon as all measurements available and has the lowest running time than these existing delayed filters. One simulation, including two cases, is utilized to illustrate the design procedures proposed in this paper.