An imaging scheme based on temporal and spatial correlations is proposed for moving object. The motion of object is divided into a series of frames, and the first frame is selected as the target object of spatial correlation. The relative position information of the moving object between any two adjacent frames is encoded into time signal, and the signal becomes the temporal correlation target. With the spatial and temporal correlation imaging techniques, the first frame image information and any inter-frame time signal can be obtained. According to the set rules, the time signal is later converted into the spatial relative position of the moving object between frames, and the moving object is shifted based on the first frame image to obtain the second frame image. On the basis of the second frame image, the third frame image is reconstructed by combining the spatial relative position information of the moving object recovered by temporal correlation. And so on, the moving object imaging is obtained by integrating all frames information finally. The feasibility of the proposed scheme is verified by numerical simulation. Compared with the existed correlation imaging scheme for moving objects, the proposed scheme reduces the data amount and reconstruction time of multi-frame correlation imaging of moving objects, and provides a new research method for exploring the imaging of the moving objects nonlocality.
Sparse decomposition expresses a signal as a linear combination of a small number of atoms in a redundant dictionary. The accuracy of the decomposition has an important influence on its wide application. A sparse decomposition method based on quantum evolution algorithm is proposed. The Gabor atoms are encoded by the enhanced qubit probability amplitude. Simplified gradient evolution operation and generation-by-generation reduction mutation operation are used to update the individual population. And the inner products of the residual signal of sparse decomposition and Gabor atoms are used as the fitness to filter out the best atoms for each sparse decomposition. Two experiments on sparse decomposition of simulation signals and the fault feature extraction experiments of the bearing vibration signals are carried out. It’s proved that the proposed method has a higher decomposition accuracy than the other methods.
In single image, in order to recover the image in the foggy weather faster, and make it suitable for both foggy and haze weather, the method of dark channel prior and the Retinex method based on the theory of human vision are combined and improved. Estimation of atmospheric light intensity in the dark channel prior is improved and the color of haze image is rectified in the method, which make it suitable for both the fog and haze image. In addition, the transmissivity estimation in the method of dark channel prior is simplified. The simplified dark channel prior method and the Retinex algorithm are combined, which achieves real-time processing of the fog and haze image. Based on the experiment, this method has preferable efficiency on processing the fog and haze image in the application of monitoring road, while the real-time speed is also guaranteed.
In order to study the effect of extreme temperature environment on pointing accuracy of tracking telescope, the finite element analysis software ANSYS Workbench is used to establish finite element model of tracking telescope frame. By steady-state thermal analysis, the temperature field distribution of frame is obtained under the action of solar radiation, air convection, heat generation of electric device, and heat conduction in high and low temperature environment, while the thermal deformation of frame under the action of the corresponding temperature field is obtained by static structural analysis. The results show that the slant angle of the frame set of axes are all less than 30′′ under high and low temperature working condition, which is within the allowable error range. It is indicated that the azimuthal rotating axis, pitching rotating axis and collimation axis of tracking telescope frame do not deflect basically, and pointing accuracy of tracking telescope is almost unaffected in extreme temperature environment.
Constructing exact solutions of cubic nonlinear Schrodinger equation is helpful to understand the relevant physical background of the equation. Some exact solutions of cubic nonlinear Schrodinger equation, such as hyperbolic function solutions, trigonometric function solutions and rational function solutions, are obtained by using the generalized exp[-φ(ξ)]-expansion method and symbolic computation system-Maple. These new solutions contribute to the application in optical communications. It can be seen that this expansion method is very effective for solving nonlinear partial differential equations in mathematical physics problems.
The adjustable generation of dissipative soliton resonance pulse and randomly chirped pulse in a square-wave fiber laser is proposed and demonstrated. A chirp measurement system is employed to investigate the output chirp characteristics. The results show that the adjustable generation of dissipative soliton resonance pulse and randomly chirped pulse can be achieved by adjusting the polarization controller inside cavity. The spectrum of dissipative soliton resonance pulse has a pedestal with two steep edges and a narrow spike, and the corresponding pulse chirp is linear and low at the central part while nonlinear and large at the edges. The chirp of randomly chirped pulse is irregular, and the spectral shape and width hardly change with the pump power.
The experimental results using a new scheme of stimulated Raman shortcut-to-adiabatic passage (STIRSAP) to implement an atom interferometer and improve its robustness are reported. The fringe contrast of the Ramsey atom interferometer using STIRSAP is analyzed. Compared with the traditional Ramsey interferometer using stimulated Raman adiabatic passage, the adiabatic passage is speeded up in the STIRSAP, and the contrast of the atom interference fringe is improved. By tuning the intensity of pump and Stokes light pulse, the phase shift of the atom interference fringe caused by the AC Stark effect is investigated. The experimental results show that the STIRSAP can effectively suppress AC Stark effect in the atomic interference, and thus improve the robustness of atom interferometer.
The spontaneous radiation of single photon in optomechanical system is investigated by using the microscopic master equation and damping bases method. A mechanical vibration mode and an optical cavity mode are coupled through radiation pressure in typical optomechanical system. Compared with the quantum optical master equation, microscopic master equation can describe the decay of energy eigen-state and deal with the problems related to the decay process more accurately. In the study of time evolution of the single photon spontaneous emission process, the damping bases method is used to solve the microscopic master equation. The mean photon number calculation results of cavity mode show that the probability-superposition of decay process of excited states determines the spontaneous radiation of single photon in optomechanical system. In addition, the microscopic master equation can also be used to deal with some related problems in ultrastrong coupling optomechanics.
Quantum key distribution uses quantum mechanical properties to ensure communication security. It enables both sides of the communication to generate and share a random, secure key for encrypting and decrypting the transmitted data. Measurement device-independent quantum key distribution (MDI-QKD) is an important part of quantum key distribution (QKD). It can solve the security vulnerabilities caused by measurement devices in QKD protocol and extend the communication distance while guaranteeing the security of the protocol. The principle of quantum teleportation in quantum networks is analyzed. According to the particularity of MDI-QKD protocol, quantum teleportation is applied to MDI-QKD protocol. The protocol transmits the quantum states prepared by Alice to David via teleportation in quantum networks, and then David and the other side of communication, Bob, run the MDI-QKD protocol together. The realization flow of MDI-QKD protocol based on quantum teleportation is described and the fidelity parameter of quantum state is introduced. The key rate of MDI-QKD protocol is analyzed. Simulation results show the gain effect of quantum teleportation on MDI-QKD protocol is very obvious, which can greatly extend the secure transmission distance of the key and ensure that the security protocol does not depend on the measuring equipment. All attacks on the measurement side of QKD system are effectively avoided.
Zhao et al . proposed a quantum teleportation scheme for an unknown six-qubit entangled state using an eight-qubit cluster state as a quantum channel. In their scheme, the sender needs to operate an eight-qubit von-Neumann projective measurement. Some improvements have been made to their scheme, which uses a four-qubit cluster state as a quantum channel to transmit the unknown six-qubit entangled state. In the improved scheme, to complete the task of quantum teleportation, the sender only needs to perform simple gate operations and single-qubit measurements, and the receiver needs to perform appropriate unitary operations and introduce four auxiliary particles. The principle verification experiment of the proposed scheme is carried out on the cloud-based quantum computing platform of IBM company. Compared with the previous schemes, the proposed scheme has the advantages of low resource consumption, high transmission efficiency and easy experiment implementation.
The security performance of quantum key distribution protocol mainly refers to the maximum secure key generation rate that the protocol can support under certain channel conditions. Depolarization channel is a common channel model in quantum information theory, which can effectively illustrate the disturbance of quantum states transmission in quantum channel. The security performance of BB84 protocol and device-independent protocol in depolarization channel is deduced and simulated by using quantum information theory. For the given depolarization quantum channel parameters and channel attenuation parameters, the security key rates of the two protocols under different channel transmission distances are given in combination with the decoy state scheme. The results can be used to theoretically simulate the security key generation rate under the condition of long-distance quantum key distribution, which establishes the theoretical basis for further security analysis and experimental implementation.
By exploring the basic inequality, the explicit expression of the average failure probability of the probabilistic m→n quantum cloning of two quantum states with arbitrary a prior probability is given. Results show that when the number of copies approaches infinity, the probabilistic quantum cloning converges to the optimal unambiguous quantum state discrimination. The average failure probability depends on a prior probability, which makes the copies of one of two states can not be always obtained for some a prior probability. By enhancing the average failure probability, the copies of two states can be always obtained for arbitrary a prior probability.
In order to solve the problem of two-dimensional quantum circuit qubit nearest neighbor constraint in some quantum techniques, a priority-based nearest neighbor interaction cost measurement model is proposed. The optimal layout of the qubit in two-dimensional architecture is obtained based on the harmony search (HS) algorithm and then the insertion of the SWAP gate is performed by the given local sorting method. Finally the quantum circuit realizes the nearest neighbor interaction under the two-dimensional architecture. The proposed algorithm is verified by experiments and compared with the latest related results. The experimental results show that the SWAP gates in proposed method is reduced by 14.42% on average compared with that in the two-dimensional grid architecture reported in the literatures.
According to Beer’s principle, the distribution of heat radiation of an object to the surrounding space is cosine to its radiation direction. Consequently, obvious differences among the received infrared radiation is ubiquitous and even results in the error of infrared radiation temperature measurement, owing to the relative position relationship between the measured target and detector. To address the issue, the relation of target position to the angle coefficient of detector is firstly characterized quantitatively. A modified model of the amount of infrared radiation is subsequently proposed. Through the modified model, a quantitative compensation scheme for the amount of detector radiation is implemented from target radiation. Moreover, to test the reliability of the proposed method, an experimental measurement to derive the amount of radiation from uniform light is carried out by using the infrared detector. The results show that as the relative angle between the detector and uniform light increases, the gray values from the measurement of detector to uniform light under different θ-angles remarkably decreases. The relative error is lower than 0.04 after the quantitative compensation for the measurement of detector. The proposed method does improve the accuracy of infrared radiation temperature measurement and enhance the stability of test technology. It can provide a guidance for the error correction of infrared radiation temperature measurement.
The atmospheric aerosol PM2.5 is the main factor in the formation of atmospheric haze, and has become the chief pollutant in most cities of China. Atmospheric particulate PM2.5 sample collection in Zhengzhou, China is carried out for almost one week before the eve of the 2014 Spring Festival . By using the partial least squares (PLS) multivariate quantitative analysis model, attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR) of the water-soluble ions SO2-4, NO-3 and NH+4 in Zhengzhou is analyzed, and the results are compared with those of ion chromatography(IC). The pollution characteristics and trend of SO2-4, NO-3 and NH+4 before the eve of the 2014 Spring Festival in Zhengzhou are analyzed, and the pollution sources of aerosol are preliminarily determined.
By using the Lee-Low-Pines (LLP) unitary transformation, linear combination operator and variational method, the ground state energy formula of polaron in monolayer black phosphonene on polar substrate in uniform magnetic field is derived, and the effects of magnetic field and substrate material on the ground state energy of the polaron in monolayer black phosene are investigated. The numerical calculation shows that the ground state energy of the polaron increases with the increasing of the magnetic field strength when the vertical distance between the substrate and monolayer black phosphonene and the cutoff wave vector remains unchanged, and decreases with the increasing of the phonon energy of the substrate material. The ground state energy of the polaron on different substrates is different, but the variation law is consistent. When the vertical distance and magnetic field strength remain unchanged, the ground state energy of the polaron increases with the increasing of the cutoff wave vector. These results indicate that the ground state energy of the polaron in the monolayer black phosphonene is related to the external magnetic field and substrate material.
A broadband difference frequency generation (DFG) comb with high conversion efficiency based on a mode-locked erbium-doped fiber laser and GaSe crystal is presented. The DFG comb adopts all-polarization-maintaining fiber structure to obtain fundamental frequency pulses with high linear polarizations degrees, and the nonlinear pulse fiber amplification technique is utilized to achieve wide bandwidths, short durations and high peak powers, for the two-color fundamental pulses. This offers the DFG comb the properties of wide bandwidth and high conversion efficiency, and the stability of the DFG process. The experimental results show that the achievable bandwidth of the DFG comb near 8.15 μm reaches 1.7 μm, only limited by the phase-matching acceptance bandwidth of the crystal, and the corresponding DFG conversion efficiency is as high as 1%, much higher than that for the fiber-type DFG comb reported so far, which is about 0.4%.
The simultaneous transmission sharing a same few-mode fiber of classical and quantum signals can be realized by using mode division multiplexing. In order to analyze the quantum signal influenced by classical optical signals due to optical fiber nonlinear effects during transmission, the relationships between the crosstalk power caused by nonlinear effect and fiber length, as well as the power of classical optical signals are investigated, and a quantum bit error rate model under the influence of nonlinear effect is constructed. The simulation analysis is carried out for the three modes optical fiber system, and the effects of fiber length and classical optical signal power on the quantum bit error rate are discussed. Simulation results show that when the signal wavelength is 1550 nm and the power of the classical optical signal is -10 dBm, the quantum safe communication distance can reach 155.7 km, among which the power of the classical optical signal is the biggest factor influencing the safe communication distance.
The synchronization and parameter estimation of an uncertain heterogeneous chaotic system with single-drive and multiple-response are investigated. By using Lorenz system to drive Yang system and Liu system simultaneously (parameters of the three systems are unknown), an uncertain heterogeneous chaotic system with single-drive and multiple-response is constructed. Based on Lyapunov stability theory and adaptive control method, the expression of adaptive controller and updating rule of parameters are given. Two different forms of mixed synchronization of the chaotic system with single-drive and multiple-response are investigated by introducing the scaling factor, and the unknown parameters are estimated. The feasibity of the method is proved theoretically. The simulation results show that the uncertain heterogeneous chaotic system with single-drive and multiple-response can achieve better synchronization and accurately estimate the values of all unknown parameters in the system.
An integrated optical waveguide grating coupler using gallium nitride and azobenzene polymer composites is designed, and the characteristics of the device are analyzed by simulation. An integrated optical waveguide directional coupler is constructed using two symmetric gallium nitride ridge optical waveguides on a gallium nitride aluminum substrate, and an azobenzene-containing polymethyl methacrylate polymer is coated as a cladding. Based on the photosensitive properties of the azobenzene polymer, a Bragg grating is fabricated by periodic illumination in the region between the two ridge waveguides. The coupling between the modes in the grating coupler is analyzed by the coupled mode theory. Using the coupled mode equations, the output characteristics of each port of the grating coupler are simulated, including the output of each mode as a function of the transmission distance and the amplitude variation under different coupling period conditions. The spectral characteristics of the multi-coupling-period grating coupler are further analyzed, which provides a new scheme for realizing the operation of complex spectrum signal in integrated optical path.