Quantum information theory, which mainly involves in quantum communication and quantum computation, now is the hot research field of physics. The fundamental theoretical frame of quantum communication and quantum computation was introduced, which include quantum entanglement, quantum no-cloning theorem, quantum key distribution, quantum teleportation, quantum parallel computing, quantum computational means of Shor and Grover. The experimental progress in the field was also introduced.
We briefly introduce the protocols of realizing quantum information process, mainly focus on the cavity quantum electrodynamics (cavity QED), including its background, features, difficulty and the progress. We also introduce the recent progress of cavity QED in State Key Laboratory of Quantum Optics and Quantum Optics Devices at Shanxi University
We calculated the mutual information among Alice, Bob and Eve with theory of the quantum measurement channel, the information theory and the theory of Markovian chain series channel, for B92 protocol in the case of opaque eavesdropping. A new criteria for checking Eve is estimated.
A scheme to teleport an entangled state by two W states is proposed. It is proved that the probability of successful implementation teleportation is 4/9. In the process of the teleportation, the successful probability is not affected by the order of operations.
Based on the fidelity conclusions of employing two-mode squeezed vacuum state for the entangled channel to teleport coherent state, continuous-variable quantum teleportation employing bright two-mode squeezed state for the entangled channel was studied. The results indicate that it's fidelity can be further improved by choosing appropriate parameters, in addition, we can fulfill that fidelity is 1, that is, not anamorphic quantum teleportation of coherent state under particular conditions.
A scheme for teleporting an unknown quantum state via a partially entangled particle pair is proposed. We show that teleportation can be successful realized with unit fidelity but less than unit probability if the sender performs a rotational operation on the teleported qubit and then performs computation basis measurements on the teleported particle and the half of the entangled particle pair respectively. The probability of successful teleportation is determined by both Schmidt coefficients of the entangled pair. This method can be generalized to the teleportation of an arbitrary and unknown multi-qubit state.
The evolution of fidelity of quantum information in pair atoms of entanglement state interacting with coherent light field was investigated. The expression of fidelity of quantum information in J-C model with many-photon transition was written out. Time-evolution of fidelity of quantum information in J-C model with one-photon transition or two-photon transition was compared.
A new scheme is proposed to implement quantum logic gates such as single qubit rotation gate, two qubit controlled-phase gate and controlled-NOT gate, using the method based on a quantum system, which is composed of the one-dimensional trapped-ion motion and a single cavity field mode. In the present scheme, computation basis is composed by the internal ionic state and the cavity state by the connection of motional state. Furthermore, Lamb-Dicke limit is not required.
Some transformations of quantum information experiment, e.g. swapping, by using the lowering and raising operator in Fock space were studied. And their representation in a new way was obtained.
We set out to find the generic multipartite GHZ state from the multipartite entangled coherent states, which is composed of fermions. The figures of quasi-probability distribution of Wigner function of the GHZ state are worked out. The interaction energy of GHZ is computed through the eigenvalues of their eigenstates. When the phase factor changes from 0 to π, the variance of the configuration and interaction energy is analyzed. We compute the Wigner function using the Qotoolbox of Matlab computer language, which creates the orthogonal bases on the vector space. The way in which we compute the Wigner function is more convenient than others. Finally we validated the principle of identical particles, which is one of the assumptions of quantum mechanics.
The squeezing properties in the system of the coherent optical field interacting with two identical two-level atoms are studied via time evolution operator and numerical method . The results indicate that the squeezing of optical field depends on the degree of entanglement of two identical atoms. At certain particular time, for some special numbers of photons, optical field can be squeezed entirely in any entangled state of two atoms. In some cases, the optical fields can not be squeezed.
The case that one of the two entangled identical two-level atoms interacts with a single-mode field among three-body entanglement was mainly considered. The results show that in initial the more the degree of entanglement of the two entangled atoms have, the more oscillation of the entanglement measure will have,and the more times of the maximally entanglement measure will obtain. Meanwhile, it was found that entanglement measure will be reduced when atomic coupling coefficient is larger than coupling coefficient between field and atom.
By solution of Schrodinger equation and numerical calculations, the light squeezing effects in the system of the two-mode entangled coherent state optical field interacting with a V-type three-level atom was discussed. The results indicate that the light squeezing effects depend on the degree of entanglement of the two-mode entangled coherent state optical field, the detuning, mean photon numbers and atomic initial state.
The time-evolution characterizations of the population and dipole squeezing of two-level entangled atoms in Bell states interacting resonantly with a single-mode cavity field in the Fock state were presented. The results show that Bell states composed of two identical atoms can be partially distinguished.
The behavior of spontaneous emission of atoms in microcavities is significantly different from that in free space. The spontaneous emission is controlled by microcavity, it can be enhanced or restrained, even can become a reversible process. Interaction of the cavity field with an atom is expound by the cavity quantum electrodynamics. We briefly introduce the basic ideas of this subject and its recent progress, also introduce an important application of microcavity-the threshold-less laser.
Following the Kinana-Daoud formalism, the generalized Klauder-Perelomov coherent state of anharmonic oscillator is constructed. The completeness of the state and the properties of the Hilbert space are disscussed. It is shown for the research of Mandel Q parameter that KP coherent state coincides with the super-Poissonian. In the some conditions the KP coherent state exhibits both squeezing and antibunching.
Two independent phase operators were denned and corresponding eigenstates in the supersymmetric harmonic oscillator's two-mode phase space were obtained.
The variation features of double-deck rectangle phase grating were theoretically investigated, and the conditions for split of two bunches of light, three bunches of light and four bunches of light were discussed. By computer simulation, optiomal parameters were put foreward.
The structure and spectrum of the Cr4+:YAG crystals were investigated and the heat effect of the Cr4+:YAG crystal in theory in the optical radiation was analysed. The prospects of the Cr4+:YAG crystals in the applications of the solide-state lasers were also presented.
By using a model of a mode-lock fiber laser with a nonlinear polarizer, numerical simulation of pulse propagation in birefringent fiber was carried out. As a conclusion, the alignment angle of the polarizer with fast axis is proposed the important elements that influence the uniformity of the pulse. Experimentally, 1.5 ps mode-locked pulse series centered at 1556.8 nm were obtained.
The decoherence characteristics of two-level atoms, which are put in a thermal reservoir and under the degenerate two-photon Jeynes-Cummings model including Stark shift, are studied by calculating the reduced density matrix elements of the interaction system. The restriction equation that must be satisfied by the external controllable driving field when the decoherence is to be eliminated is also derived.
The quantum properties of light in the system of two coupling atoms Raman interacting with single-mode squeezed vacuum field in Kerr medium are studied by means of quantum theory .The influences of the coupling constant x are discussed.
The evolution properties of Mandel Q(t) with time in the system of V-type atom interacting with squeezed coherent light field inside a high Q with a Kerr medium was investigated. It was shown that the intensity coefficient μ of Kerr medium, the squeezed light field factor γ, the coherent vibration amplitude |α|2 of the light field and the coupling parameter A of the field-atom influence the quantum collapse-revival periodicity of the evolution curves of Mandel factor Q(t). Meanwhile, they all influence the states and properties of the photon statistical distribution of radiation field.
The quantum wave function of mesoscopic RLC circuit with power source is obtained by the method of representational transformation, and with the wave function, the quantum fluctuation of the mesoscopic circuit was obtained. Meanwhile, the quantum effect of mesoscopic circuit with power source is investigated using the double wave function. By comparing between two kinds of methods, we confirm that the fluctuation is connected with the state of a circuit. This can be seen from the method of double wave function. The average values of ensemble solved by double wave function are just the expected values solved by the method of representational transformation.
The quantum effect of mesoscopic inductance-capacitance coupled circuit with mutual inductance was investigated by canonical transformation and unitary transformation. The mesoscopic inductance-capacitance coupled circuit was compared with several coupling circuits. It is found that it is convenient to control the quantum fluctuations and squeezed effect by adjusting mutual inductance coupling coefficient in mutual inductance circuit with coupling capacitance. Uncertainty relations of charges and conjugate currents are related to canonical transformation parameter φ and uncertainty relations parameter ξ. When ξ→1 or φ→nπ/2, (n = 0,1,2,…), the uncertainty relations approach minimum value h/2.
The N-th power H-squeezing effects of photon field for the photon-added two-mode squeezed vacuum state a+mb+m|ξ> were numerically studied. It is shown that the photon field can exhibit the N-th power H-squeezing effects (N = 1, 2, 3, 4, 5,…);for higher power H-squeezing (N ≥2) and larger γ (γ is the squeezing parameter), as m increases, the N-th power H-squeezing effects increase.
A new solid sample inlet interface was mounted on a homemade time-of-flight mass spectrometer, and the ion source structure was rebuild. Several Rhodamine dyes was analyzed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. A KrF excimer laser output at 248nm is used to induce the desorption ionization process. The matrix material 2,5-dihydroxybenzoic is used in all experiments. Characteristic fragmentation mass spectra of these species are detected. The influence of laser power and the optimal matrix/analyte molar ratio on repeatability and resolution of the mass spectra was also studied. It was found that one can use a single wavelength laser to carry out the detection of numerous species if the analyte and the matrix can be dissolved in the same solvent.
AlGalnP/GalnP MQW samples of different numbers of wells were grown by LP-MOCVD and their Raman spectra were measured. Because of the doped current spreading layer, Ohm touching layer, top confining layer and bottom confining layer, coupled elec-tron(hole) -plasmon-LO-phonon modes are observed in Raman spectra. According to the Raman selection rule and the PL measurement, it is reasonable to evaluate the quality of AlGalnP/GalnP MQW by analyzing the relative intensity ratio of A1P-LO/TO.
The supercontinuum generation in the dispersion-flattened and decreasing fiber was theoretically investigated. The research indicated that the dispersion characteristic of the fiber has influence on pulse evolution and supercontinuum generation. Because the dispersion slope of the fiber at the pump wavelength is equal zero, the pulse keeps symmetry while it propagates in the fiber, and the symmetrical supercontinuum is resulted in. It is more suitable for broad supercontinuum generation when the dispersion curve of the fiber is flatter and the distance between the two zero-dispersion wavelengths of the fiber is farther from each other.
A photonic crystal narrow pass band optical filter was presented, which is made of two pieces of uniaxial anisotropic photonic crystals with different photonic band gaps. The principle for the system is to arrange properly the band gaps of the two photonic crystals so that a small narrow pass band appears in the combined photonic band gap region. The optical characteristics such as transmission and polarization of this periodic structure in different incident tangos and refractivity conditions were analysed. The results show that if the uniaxial anisotropic photonic crystal has a large ratio of refractivities or combined with high refractivity isotropic media, it may have a narrow pass band gap, and our numberical investigations show that this kind of structure is feasible for narrow band optical filtering.
A new two wavelength fiber sensor for measuring surface roughness was introduced. The structure, working principle and characteristic of the fiber sensor were described. The experimental result indicates that the fiber sensor has good linearity, strong ability of antijamming, higher accuracy and usage for small surface measuring. Furthermore, error formula of the fiber sensor is induced, measuring error caused by temperature flux is numerically discussed.
A new type of method for estimating extinction efficient boundary values with least square fitting for inversion of slant angle lidar measurement is reported. In cloudless weather, the boundary values of extinction is calculated by fitting lidar return signal. For cloudy weather, firstly, the measured region is divided into cloudy and cloudless section. Then it is assumed that the cloudless region is homogenous circumstance. The boundary values of extinction is calculated by fitting lidar return signal except the cloudy region. Finally, the atmospheric extinction coefficients are inversed with Klett's inversion algorithm and the boundary values. The simulation results are close to the real atmospheric conditions.
The design of radar digital signal optical fiber transmission system's transmitter module was introduced. Based on the character of the radar signal, the transmission of radar multi-data was realized using a special frame.