The relationship between quantum state control and matrix decomposition is reviewed. The matrix decomposition newly applied in quantum information science,i.e. Cartan decomposition based on group theory and cosine-sine decomposition based on numerical linear algebra,is introduced firstly. Then the current research situation and the results in this area are reviewed. These results play important roles in quantum entanglement dynamics,the control of quantum states and optimization of quantum circuit.Finally,the Cartan decomposition of a 2-qutrit logic gate is given.
Ultraviolet photolysis of methylamine was carried out by 233~243 nm laser. The resonant enhanced multi-photon ionization(REMPI)mass spectrum was obtained and studied. The laser power dependences for major peaks M30,M28,M15 were measured,and compared with calculated entropies density functional theory using quantum calculation. Thus those three major fragments were identified.
The concept of vectorial nonparaxial Hermite-cosine-Gaussian(HCosG)beams is introduced and their free space propagation equations are derived analytically by using the vectorial Rayleigh-Sommerfeld diffraction integrals and the on-axis and far-field expressions as well as paraxial propagation formula are obtained in free space. Numerical calculations and analysis show that,the f-parameter and decentered parameter play important roles in determining the nonparaxiality of vectorial HCosG beams. In addition,the on-axis intensity distribution is relative to the beam order and its parity.
The design method of a Newton optical system with a zero-power corrector,where the stop is before the primary mirror,is discussed in detail. By moving the stop,changing the eccentricity of primary mirror,selecting the power of the corrector,and calculating the rays of the system concerned,the optimized optical system solution is obtained,various design curves and results are given,and the optical system is evaluated. Take Newton optical system for an example,where the clear aperture Φ is 300,relative aperture A is 1/2,field of view θ is ±5°,the corrector's power ■11 is 5,its aberration coefficients S1 can achieve 0.000002λ,S2 is 0.000025λ after optimization,the wavefront aberration is 0.3174λ at 0° field of view,and 90.9861λ at ±5° field of view.
A three-dimensional quantum cellular neural network is proposed by using the quantum cellular automata as neuron cells. The new structure of the quantum cellular neural network contains two layers of quantum cellular automata array and introduces concepts of A cloning templates,B cloning templates,and thresholds. The proposed quantum cellular neural network can perform the functions of the logic AND,OR,NOT operation,and edge extraction operation by using the polarization of quantum-dot cell as pixel value and selecting different cloning templates and thresholds. The MATLAB is employed to simulate the four operations and the results demonstrate the validity of the proposed quantum cellular neural network.Moreover,compared with the traditional cellular neural networks,the quantum cellular neural network possesses the advantages of the simplified interconnection,the extremely high packing densities and the extremely low power consumption.
Symmetries similarity reductions and new exact solutions to the(2+1)-dimensional Boiti-Leon-Manna-Pempinelli(BLMP)equation are obtained by using Lie group analysis method,including rational solutions,hyperbolic function solutions,Jacobi elliptic function solutions and triangular periodic solutions.The infinte conservation laws of the(2+1)-dimensional BLMP equation are found.
Actively mode-locked fiber lasers based on the semiconductor optical amplifier(SOA),which are capable of generating ultra-short pulse train with high quality and high repetition rates,received considerable attention. After considering the nonlinear polarization rotation in the SOA,a theoretical model of the harmonic mode-locked fiber ring laser based on SOA is established. Using this model,for different bias currents of the SOA,the influences of the nonlinear polarization rotation in the SOA on the shape,peak power,and pulse width of the pulse output from the harmonic mode-locked fiber ring laser are investigated theoretically. Numerical results show that the mode-locked pulses whose peak power and pulse width are 0.16 mW and 6 ps for the low currents,0.56 mW and 19.8 ps for the high currents respectively,can be obtained for the harmonic mode-locked fiber ring laser.
The numerical method is used to solve the rate equations when the stimulated state absorption of saturable absorber is considered. The passively Q-switched output pulse energy as a function of the output reflectivity for several initial transmissions of the absorber is demonstrated. The output parameter is also demonstrated when the laser operates at maxim output energy. From numerical results of rate equations the output energy is estimated,and the key parameters of the the Q-switched lasers such as initial transmissions of the absorber and the output reflectivity are optimized. Finally,a Q-switched Ruby laser experiment data are analysed to illustrated the optimized results of the parameters.
The fluctuation-dissipation between three-level Λ-type atoms and environment(thermal radiation field)in thermal equilibrium is discussed firstly. The equations of motion for the atomic density matrix elements are derived by using the system-reservoir interaction theorem in the Markovian approximation. The thermal equilibrium steady-state is obtained. The quantum noise of probe laser in the electromagnetically induced transparency(EIT)is studied by using the fully quantum theory. It is found that quantum noise comes from the excited-atom density and the detuning of drive laser. So realizing EIT in the cold atomic system and reducing the detuning of drive laser are the keys to control quantum noise.
The security of quantum key distribution(QKD)networks based on weak coherent pulses and optical node is analyzed.In this QKD network,an eavesdropper can launch a path-attack on the quantum channel to eavesdrop quantum information. Path-attack will not change quantum key generation rate and not destroy the photon number distribution in a weak coherent pulse,moreover,it can not be detected under the high quantum channel loss. The result indicates that even the decoy states skills cannot detect this kind of threat,also this threat is proportional to the average photon number. Therefore,the influence of the path-attack must be considered when designing the quantum key distribution networks.
A method of measuring the exchange constant J of two-qubit system is proposed. The energy levels and eigenvectors are calculated by adiabatic approximation. The length of polarization of this system is obtained,and the value of exchange constant of symmetric system is found to equal to the value of z component of external magnetic field at the level crossing. In addition,the concurrence of each eigenvector accords with the measurement of Von Neumann entropy for symmetry system.
The quantum reduced entropy evolution of a V-type three-level atom interacting with the twomode odd-even entangled coherent field is investigated. The effects of the detuning,mean photon numbers of field,the atom's initial state and the degree of the entanglement of the two-mode odd-even entangled coherent fields on the entropy are discussed. The results show that the oscillation of the entropy presents collapses and revivals with the increasing of the detuning or the mean photon number. The mean-value of field entropy decreases with the increasing of the detuning. But it increases with the increasing of the mean photon number. The mean-values of field entropy are higher when the atom is initially in excited state or superposition state than that of in ground state. The mean-value and the amplitude of field entropy decrease with the increasing of the degree of the entanglement of the two-mode odd-even entangled coherent fields.
Considering two two-level atoms(A and B)initially in the EPR state,atom B is put into one cavity prepared in coherent superposition state. When atom B flies out of the cavity,an arbitrary state measurement is carried out on it. The law about the effects on the dipole of atoms A exerted by light field intensity and superposition coefficients is obtained,and the result also shows that the dipole squeezing of atoms A can be achieved under certain conditions.
The fidelity evolution of quantum state under the interaction of the binomial photon field and atomic Bose-Einstein condensate(BEC)are studied by full quantum theory. The influences of the interaction among atoms of BEC,the average atomic number of atomic BEC and the parameter of light field on the fidelity are investigated. The results indicate that the amplitude and oscillated period of fidelity of quantum information for the interaction system can be controlled by choosing the intensity of the interaction among atoms and the average atomic number on the ground state. And the change of the light parameter only plays a role on the fidelity effect. The higher fidelity can be obtainedby choosing suitable parameters.
Considering two-mode entangled coherent light fields,one mode of the fields was poured into the cavity with a two-level atom and interacted with it by k photons non-resonantly. During the course of cavity-QED evolution of the total system,a selective measurement of the atom was carried out. Through manipulating the evolution time and the parameter of the coherent field which interacted with atom,in certain conditions,the non-classical light such as anti-bunching and squeezing state can be generated,and the strength of non-classical property can be changed. In this way by using the technique for cavity-QED with k photons non-resonantly and the entangled correlation between the coherent light fields,controlor change the non-classical properties of coherent light fields remotely without direct measurement was implemented effectively.
By using the multi-photon nonlinear Compton scattering conception and the model of the nonlinear scattering between an electron and a photon,the propagation equations of the laser amplification of the coupling chirped-pulse in the total internal reflective photonic crystal fiber are built. By theoretical analysis and numerical simulation,the influences of Compton scattering on the self-phase modulation of TIR-PCF are studies. The results show that the self-phase modulation of the coupling chirped-pulse laser is strengthened by the Compton scattering. The induction electrical polarization strength of the fiber,the density of the reversed particle number and gain increase,the phase changing accelerates,and the excited radiation section decreases. Therefore,the gain phase movement can not be ignored.
In order to eliminate the impact of oversample-cumulating method on clarity of linear push-broom imaging,with the transition of aperture function,a deblurring method was put forward to cumulate the pixel in the same sample position,thus the aperture function in push-broom direction was equal to the linear direction,and the impact of pixel shift in cumulating was eliminated. With the sample-cumulating rates of 4,at Nyquist frequency the value of pixel transfer function was increased by 7%. Through simulating oversample-cumulating test,the results show that the deblurring algorithm can be achieved. This simple algorithm only needs a small number of adders,with slightly modified FPGA codes,then the camera can be put to use.
In the Ohmic contacts of LED electrodes,carriers have different transmission mechanisms between metal electrode and semiconductor. By simulating transferring mechanism of carriers in metalsemiconductor interface,the impact of the interfacial layer and barrier potential on series resistance and leakage current of LED is discussed. Resistance of interfacial layer can be ignored comparing with LED's series resistance because it is very small. With the aging of the LED,the interfacial layer and defects can result in very serious leakage current,let reliability and stability come down,and also provide the theory basis to the LED invalid mechanism.
In both time and wavelength domains of the fiber-optic channels,a novel construction scheme of two-dimensional quadratic prime code(2D-QPC)for two-dimensional optical code-division multiple access system is proposed. The designing process of 2D-QPC is given in detail;the autocorrelation and crosscorrelation of 2D-QPC are analyzed based on finite Galois Theory. After that,the system capacity and BER performance of optical code-division multiple access(OCDMA)system employing 2D-QPC as signature code are calculated according to the“HIT”method. The result indicates that 2D-QPC has better auto and cross correlation properties compared to one dimensional synchronous quadratic prime code(1D-QPC)(autocorrelation from 1 to 0,cross-correlation from 2 to 1),and 2D-QPC also has larger system capacity,which is p+1 times as that of 1D-SQPC when they occupy the same bandwidth and have the same bit-rates.
The power confinement factor of the fiber with cladding made of uniaxial crystal material whose optical axis is parallel to the axis of fiber was investigated by means of numeric solution and the influence of kcl on the reflectivity of this kind of fiber Bragg gratings was physically interpreted with mode characteristics.The calculated results indicate that for HE11 mode,more power is transmitted by the core of the fiber with cladding made of isotropic material than that with cladding made of uniaxial crystal material and the degree is dependent on the parameter kcl,the reflectivity of the fiber Bragg grating with cladding made of uniaxial crystal material is much higher than that with cladding made of isotropic material,the reflectivity of this kind of fiber Bragg grating is greatly influenced by the energy distribution between the core and the cladding of this kind of the fiber.
With the limit of photo-sensitization,when the channel number becomes large,it's unrealistic to fabricate such sampled fiber Bragg gratings(FBG). Phase-only sampled FBGs were demonstrated to effectively reduce the maximum refractive index modulation(MRIM). A hybrid method which employs the inverse scattering(IS)technique and the optimization strategy is demonstrated to be efficient for the design of multi-channel fiber Bragg gratings. Optimized by genetic algorithm(GA),a set of optimal constant phases are introduced to the phase responses of the multiple channels,which lead to a modified complex reflection spectrum of the multi-channel fiber Bragg grating. Then,the layer-peeling IS algorithm is applied to extract the grating index profile from the modified spectral response. By introducing a set of optimal phases to the phase response of the multiple channels,the target reflection response of the multi-channel FBG is modified,which ensures the MRIM of the N channel grating is about only √N times that of the single channel grating. The simulation results show that this hybrid method reduces the MRIM required for 8 channels to approximate √8 times that of the single channel.
A novel two-channel atmospheric pressure measurement system with optical fiber was put forward.The system consists of a two-path fiber optical fiber displacement sensor and twin metallic membrane boxes with high precision. The displacement produced by air pressure was detected with the fiber sensor. The characteristic of the system is independent of the light source. The output parameter is independent of the light,and is only dependent on the structural parameters of the fiber sensor. The signal processing circuit of the system was designed. The signal processing circuit mainly includes signal pre-amplifier,narrowband BPF,RMS converting circuit,A/D and the MPU circuit. The output characteristic curve of the system was acquired,the measurement precision is ±0.1 hPa,and the resolution is less than 0.2 hPa under the structure of the fiber sensor.