This paper studied estimation of the phase parameter of a two-state system in a squeezed bath,investigated the effects of the parameter N and the squeezing phase  of the squeezed bath on quantum Fisher information,and focused on the enhancement of the estimation precision.The results showed that,the quantum Fisher information decays with time and changes periodically with the squeezing phase .When the value of the squeezing parameter N is larger,the quantum Fisher information decays more slowly and the estimation precision can be enhanced.

Schrodinger cat state is a continuous variable quantum state,and it plays an important role in the research of fundamental physical problems and quantum information.Cat state is a superposition of two coherent states with identical amplitudes and opposite phases,which can be used as an encoded qubit for quantum computing,quantum repeater as well as quantum precision measurement.Generally Cat state is prepared experimentally by subtracting a photon from vacuum squeezed state. The generation of a Cat state is predicted by the click of a single photon detector,while the quadrature components are measured with the balance homodyne detection. Because the noise distribution of the quadrature components of a Cat state is dependent on phase,the phase jitter in homodyne detection system is an important factor on the quality of the prepared Cat state. We study the impact of phase jitter in homodyne detection on the preparation of Cat state. At first,in the case of stable phases we obtain the analytic expression of the marginal distribution of the quadrature noise of a Cat state,and get the measurement set of the quadrature components by computer simulation. Then the measurement set under the condition of phase jitter are acquired by means of transforming the marginal distribution, and the Wigner function of the quantum state is reconstructed using Maximum Likelihood Estimation. We analyze the fidelity of Cat state as well as the origin value W(0,0) of the Wigner function as a function of phase jitter amplitude. It shows that the fidelity decreases with increasing of phase jitter amplitude while W(0,0) value is insensitive to phase jitter. Furthermore, the impact of phase jitter on fidelity of Cat state is analyzed for different squeezing degrees and squeezing purities of the input states. The results indicate that the lower squeezing degree or higher squeezing purity, the smaller the influence of phase jitter on fidelity. Either a higher squeezing degree or a smaller squeezing purity will result in a more significant difference in the noise distribution of the quadrature components between the phases 0° and 90°. When phase jitter occurs, the quadrature components are redistributed in the range of phase jitter. If the distribution difference between different phases is significant, the decreasing of fidelity resulting from phase jitter will be obvious, so the fidelity of Cat state is more insensitive to the phase jitter when the squeezing degree is lower or the squeezing purity is higher. The above work can provide a theoretical guidance for the experimental preparation of cat state with high fidelity.

Using a fiber-based compact source of entangled photon pairs, we build a single-mode-fiber-coupled scheme for quantum ellipsometry, and measure the ellipsometric parameters for a 100-nm-thick silica film on silicon substrate.The signal photons of the photon pairs are reflected by the sample under test.By performing the two-photon coincidence counting measurement for the entangled states after the reflection, we obtain the ellipsometric parameters of the sample.When the wavelength and incident angle of the photons sent to the sample are 1558.17 nm and 30 °, the measured ellipsometric parameters (ψ,Δ)are 40.23 ° and 173.10 °, with standard deviations 0.046 ° and 0.403 °, respectively.The relative standard deviation of the meausred results is less than 1％, and the results agree well with theoretical predictions.

According to the difference of entanglement resources consumed by quantum nodes in different environments,the weights are used to quantify the influence of real environment on each quantum node,and the distribution of entangled particles is determined according to the weights.At the same time,a routing protocol for quantum wireless multi-hop networks is proposed based on weights.The protocol takes the utilization ratio of entangled particles as the routing metric,and establishes quantum channel through the distribution of entangled particles based on the maximum weights and the parallel entanglement exchange to realize the transmission of quantum states.The simulation results show that the proposed routing protocol can be used to find out the quantum links in the network which meet the measurement conditions,and the parallel entanglement swapping is used in the routing protocol to reduce the delay of quantum state transmission.When the number of nodes is 15,the average delay of parallel switching is 50％ lower than that of serial switching,and with the increase of the number of nodes in the link,the delay between the two will become larger and larger.The weights of the simulation nodes are all random integers of 1 to 15.Through several simulations on the links of 5 nodes,it is found that the average number of quantum states that can be transmitted by using the maximum weights entangled particle distribution method is 14,and the average number of quantum states that can be transmitted by the serial distribution method is 7.The routing scheme based on the maximum weights of entangled particle distribution can save entangled resources,maintain the load balance of the network,and prolong the service life of the link in the network.

Based on quantum game theory of single coin,combing with classical XNOR Gate, the definition of quantum one is achieved. Furthermore, the model of single-coin quantum theory is proposed to realize quantum XNOR Gate theoretically. Comparing the quantum logical bit with the classical logical one,we have acquired the method of the specific operations, that is, the logical function of quantum XNOR gate can be acted as the quantum game process of two separate quantum coins.

A density functional method(B3LYP) with 6-311++G(3df, 3pd) basis sets has been used to study the equilibrium geometric parameters, total energies, dipole moments, charge distributions, the highest occupied molecular orbital(HOMO)energies, the lowest unoccupied molecular orbital(LUMO)energies, energy gaps of CHF=CHF under different external electric field ranging from -0.05 to 0.05 a.u. On the basis of optimized configuration, the excitation energy, transition wavelength and oscillator strength in the same intense external electric field and basis sets are calculated by the configuration interaction singles(CIS-B3LYP) method. The results show that the geometric parameters of CHF=CHF molecule strongly depend on the magnitude and direction of external electric field. The total energy of CHF=CHF molecule in different external electric fields ranging from -0.05 a.u. to 0.05 a.u. first increases and then decreases. On the contrary, the dipole moments of CHF=CHF first decrease and then increase. The HOMO energy is found to decrease,while LUMO energy first increases and then decreases through the variation of the external field.The energy gaps of CHF=CHF first increase and then decrease. The excitation energies, transition wavelengths and oscillator strengths are very complicated with the change of the external electic field.

The manipulation of quantum interference using correlated phase fluctuation in an atomic system is proposed. The collisions among atoms and the coupling between the atoms and the external reservoir environment result in the random phase fluctuations of the atomic energy levels. The effect of the phase fluctuations and their correlation on the atomic coherence and quantum interference is studied. The results show that the correlated and anticorrelated phase fluctuations lead to the destructive quantum interference (suppressed absorption of the probe field) and the constructive quantum interference (enhanced absorption of the probe field),respectively. The quantum interference vanishes under certain condition,and the response of the atoms to the probe field is determined by the Autler-Townes splitting. Finally,the influence of the Rabi frequency of the coupling field on the quantum interference is studied. When the coupling field is relatively weak,the quantum interference can be efficiently manipulated using the correlated phase fluctuations. When the coupling field is strong,the quantum interference can be ignored.

The ground-state CF4 molecule was optimized using a density functional theory/B3LYP method in the 6-311++G basis set.The bond length, dipole moment, Mulliken charge population distribution, molecular frontier orbital energy and infrared were calculated.Spectral and other data, and based on this hybrid CIS method was used to calculate the first 9 excited states of CF4 molecule, and the molecular excitation energy, wavelength and oscillator strength were obtained.The study shows that as the electric field intensity increases (electric field in the range of -0.04-0.04 a.u.), the F2—C1 bond length of the CF4 molecule increases, and the remaining bond length decreases, and the dipole moment of the molecule decreases first.With the increase, the number of C1 charge population decreases first and then increases.The population of F2 charge population decreases linearly.The population of F3, F4 and F5 charge population increases linearly, and the molecular energy gap decreases.CF4 molecular structure under external electric field Symmetry is destroyed, the number of infrared absorption peaks increases, and the absorption intensity of absorption peaks changes.The first 9 excited states of the molecule are affected by the electric field.The excitation energy increases with the increase of the electric field, and then increases first and then decreases.The excited wavelength is basically a phenomenon of blue shift, followed by a phenomenon of red shift, and intense vibration of the oscillator,to make theoretical calculations for studying excited states from the spectrum.

In this paper,the topological properties of two-component Fermi gas driven by spin-orbit coupling and Zeeman field in a one-dimensional sawtooth lattice were studied.The energy spectrum of system was calculated theoretically,and some quantities such as the edge state,von Neumann entropy,entanglement spectrum and excitation energy gap were computed numerically by matrix product state (MPS).The topological properties of the system were analyzed based on these results.It was found that the presence of edge states can be used to demonstrate the topology of the system at half filling.With the 1/4 (or 3/4) fill factor although the system has a single edge state,it does not possess other features of the general topological state.Therefore,such edge state cannot characterize the topological state.

In this paper, the tunneling properties of Bose-Einstein condensates containing one fermion impurity in an optical microcavity are investigated. Based on the Hamiltonian of the coupling system between the optical microcavity and the Bose-Fermi mixture in a double well, the analytical expression of ground-state energy level difference of particle tunneling and the occupation number difference are deduced. The results show that: the coupling strength between the optical cavity and the atom has an effect on the kind of preferentially tunneling particles and the ladder pattern of particle tunneling.

Dynamical behaviors of optical beams including fundamental and multi-polar solitons in barrier-type nonlocal nonlinear system are presented. Under the influence of barrier-type nonlocality,fundamental soliton experiences periodic oscillations,and its period and degree of oscillation can be effectively controlled by adjusting the parameters of barrier-type nonlocal system. However,for multi-polar soliton,it splits into a corresponding number of fundamental solitons due to suffering from a barrier-type nonlocality; and,these fundamental solitons periodically collide each other during their propagation; their dynamical behaviors can also be controlled by adjusting the parameters of barrier-type nonlocal system.

In order to detect the light distribution of a single photon in two-dimensional plane,an array photon counter based on MAPMT has been developed.Low noise amplification of photoelectric pulse is realized by high frequency selection technology,and crosstalk between adjacent pixels is eliminated by crosstalk cancellation technology.Finally,the development of 8×8 array photon counter is completed.The test results show that the maximum count of single pixel of the array type photon counting rate is 100MCPS,the peak photon detection efficiency is about 21.2％,and the highest frame frequency is 10 kHz.Dark objects brighter than stars of the tenth magnitude can be detected steadily by a telescope on the system of the 1.8 m.

A diode-end-pumped all-solid-state continuous-wave (cw) single-frequency tunable 1 542 nm laser is designed and fabricated. The laser oscillation at wavelength around 1 542 nm is realized by tuning the gain spectrum of the Er,Yb:YAB laser system via a special coating design. The cw single-frequency laser operation is achieved by using the twisted-mode technique for mode selection. Based on the optimization of the thickness of the gain medium and the transmission of the output coupler,the laser power is scaled up to 420 mW under 5.5 W pumping. The power stability of the laser is better than ±3％ during a given 3 hours. The laser intensity noise reaches the shot noise limit beyond the analysis frequency of 3 MHz. When an electro-optical crystal and an electro-optical etalon is inserted into the cavity and controlled by high voltage sources,quasi-wavelength-tuning of the cw single-frequency laser with the range of 1 541.959 nm~1 542.014 nm is demonstrated.

Laser ranging technology has played an irreplaceable role in military aerospace and industrial fields.As one of the core components of the ranging system,the photodetector could detect very weak optical signals and perform photoelectric conversion in this system.This paper analyzes the traditional laser ranging method and its corresponding photodiode,the emerging photon counting technology and its corresponding single photon detector,summarizes and prospects the development prospect of the detection unit in the future laser ranging system.

The edge detection operator of the spot has an important influence on the quality of a laser spot,and is the premise of subsequent image processing and analysis of the laser spot.At present,the most widely used edge detection operators at home and abroad are Roberts operator,Prewitt operator,Sobel operator,Gaussion-Laplace operator and Canny operator.On the basis of summarizing several typical edge detection operators,this paper compared and analyzed the advantaged and disadvantaged of each operator,and forecast the improvement direction of future operators.