Influence of Femtosecond Laser Parameters on Autler-Townes Splitting of Three-Level Ladder Molecules

We theoretically investigate the Autler-Townes （AT） splitting in the photoelectron spectra of three-level ladder K2 molecule driven by a pump-probe pulse via employing the time- dependent wave packet approach. The dependence of AT splitting on two laser intensities and wavelengths are studied in detail. We firstly quantify these effects on peak shift and AT separation. The photoelectron spectra show double splitting with symmetric profiles, but with asymmetric profiles when the wavelength is changed. The magnitude of AT splitting increases with the pump laser intensity, but does not vary with probe intensity. The shifts of the absorption peaks and the splitting between AT doublet are predicted by using an analyt- ical fitting function when the intensity/wavelength of one of the two fields is changed. These novel results are of importance for the molecular spectroscopy and may further stimulate the first principles theoretical studies analytically.

Innovative Teaching Research on Literary Theory and Criticism

As a core compulsory course for English majors majoring in teacher education,Literary Theory and Criticism plays an important role in enhancing text understanding,cultivating critical thinking,and shaping correct values in the future development of students.Influenced by traditional teaching ideas,students have many difficulties when learning this course,such as insufficient theoretical understanding,inadequate ability improvement,and not enough investment in course learning.In response to the above issues,this course focuses closely on the fundamental task of“cultivating virtue and nurturing people”,relying on modern information technology and introducing research methods of digital humanities.This course uses“7C”teaching mode under the“three-level integration”,in which“teaching”and“education”are carried out synchronously,and“teacher”and“student”are developed together,in order to greatly enhance students’learning participation and course satisfaction.

Population Dynamics and Emission Spectrum of a Cascade Three-Level Jaynes-Cummings Model with Intensity-Dependent Coupling in a Kerr-like Medium

By using the method of eigenvectors, the atomic populations and emission spectrum are investigated in a system that consists of a cascade three-level atom resonantly interacting with a single-mode tield in a Kerr-like medium. The atom and the field are assumed to be initially in the upper atomic state and the Fock state, respectively. Results for models with intensity-dependent coupling and with intensity-independent coupling are compared. It is found that both population dynamics and emission spectrum show no indications of atom-field decoupling in the strong field limit if the intensity-dependent coupling is taken into account.

Decoupling Bang-Bang Group for Adiabatic Decoherence Control in a Three-Level Atom

In this paper, we study the control problem of adiabatic decoherence in a three-level atom. We will find the decoupling bang-bang group for various configurations, including the V configuration and the cascade type of three-levelatom subjected to adiabatic decoherence. We also give the programs to design a sequence of periodic twinborn pulses to suppress the decoherence.

Generation of the nonlocal quantum entanglement of three three-level particles by local operations

We propose a scheme to realize the nonlocal quantum entanglement of three three-level particles by using a threeparticle entangled state of three levels as a quantum channel with the aid of some local unitary transformations. This scheme can be directly generalized to the nonlocal quantum entanglement of N three-level particles.

A scheme for conditional quantum phase gate via bimodal cavity and a∧-type three-level atom

We propose a scheme to implement a two-qubit conditional quantum phase gate for the intracavity field via a single three-level ∧-type atom driven by two modes in a high-Q cavity. The quantum inforraation is encoded on the Fock states of the bimodal cavity. The gate＇s averaged fidelity is expected to reach 99.8%.

Teleportation of Three-Level Multi-partite Entangled State by a Partial Three-Level Bipartite Entangled State

We present a scheme for probabilistically teleporting an unknown three-level bipartite entangled state by using a partial entangled three-level bipartite state as quantum channel This scheme can be directly generalized to probabilistically teleport an unknown three-level k-particle entangled state by a partial three-level bipartite entangled state. A11 kinds of unitary transformations are given in detail We calculate the successful total probability and the total classical communication cost required for this scheme.

Schemes for Probabilistic Teleportation of an Unknown Three-Particle Three-Level Entangled state

In this paper, two schemes for teleporting an unknown three-particle three-level entangled state are proposed. In the first scheme, two partial three-particle three-level entangled states are used as the quantum channels, while in the second scheme, three two-particle three-level non-maximally entangled states are employed as quantum channels. It is shown that the teleportation can be successfully realized with certain probability, for both two schemes, ira receiver adopts some appropriate unitary transformations. It is shown also that the successful probabilities of these two schemes are different.

Suppression of Phase and Amplitude Damping Decoherence in a Three-Level Atom in A-Configuration Using Bang-Bang Controls

In this paper,we present decoupling bang-bang operations for the suppression of general decoherence,bothamplitude and phase damping,in a three-level system in A-configuration.We give a program to design a sequence ofperiodic twinborn pulses to suppress the decoherence in such the system.

An Analytical Solution to the Model for Single Three-Level Trapped Ion Driven by External Fields

The interaction of a single three-level trapped ion with two laser beams has been studied theoretically. With application of two successive unitary transformations, an analytical solution to this quantum system has been obtained.

Entropy squeezing for a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel with weak measurement

The entropy squeezing of a V-type three-level atom interacting with a single-mode field and passing through the amplitude damping channel is investigated in detail. Our results show that when coupled to the single-mode field, the atom in appropriate initial states can not only generate obvious entropy squeezing but also keep in the optimal squeezing state,while passing through the amplitude damping channel, the atom can generate entropy squeezing under the control of the weak measurement. Besides, it is proved again that as a measurement method for atomic squeezing, the entropy squeezing is precise and effective. Therefore our work is instructive for experiments in preparing three-level system information resource with ultra-low quantum noise.

Optical power limiting of ultrashort hyper-Gaussian pulses in cascade three-level system

Propagation of strong femtosecond hyper-Gaussian pulses in a cascade three-level molecular system is studied by solving numerically the Maxwell–Bloch equations by the iterative predictor-corrector finite-difference time-domain method.Optical power limiting behavior induced by strong nonlinear two-photon absorption is observed for different orders of the femtosecond hyper-Gaussian pulses. Pulses of a higher order temporal profile are found to have a wider power range of optical limiting but a larger output saturation intensity. Both the output saturation value and the damage threshold of optical power limiting decrease with pulse duration increasing. The decrease of the pulse area along the pulse propagation is much slower than that obtained from the two-photon area theorem due to invalidity of the slowly varying amplitude approximation and the monochromatic field hypothesis.

Radiation forces on a three-level atom in the high-order Bessel beams

The general expressions of the average dissipative and dipole forces acting on a A-configuration three-level atom in an arbitrary light field are derived by means of the optical Bloch equations based on the atomic density matrix elements, and the general properties of the average dissipative and dipole forces on a three-level atom in the linearly-polarized high-order Bessel beams （HBBs） are analysed. We find a resonant property （with two resonant peaks） of the dissipative force and a non-resonant property （with two pairs of non-resonant peaks） of the dipole force on the three-level atom, which are completely different from those on the two-level atom. Meanwhile we find a saturation effect of the average dissipative force in the HBB, which comes from the saturation of the upper-level population. Our study shows that the general expressions of the average dissipative and dipole forces on the three-level atom will be simplified to those of the two-level atom under the approximation of large detuning. Finally, we study the axial and azimuthal Doppler cooling of atoms in ID optical molasses composed of two counter-propagating HBBs and discuss the azimuthal influence of the HBB on the Doppler cooling limit. We also find that the Doppler limit of atoms in the molasses HBB is slightly below the conventional Doppler limit of hГ/（2kB） due to the orbital angular momentum lh of the HBB.

An improved SVPWM control algorithm for three-level inverter

In the traditional three-level space vector pulse width modulation(SVPWM)algorithm,the sector judgment is computationallycomplex since the sector is divided into triangles and hexagons.In addition,the switching frequency is high becausethe seven-segment switching sequence is adopted.For this reason,a new SVPWM control algorithm for three-level inverteris proposed,in which the sector judgment is simplified by dividing the sector into quasi hexagons?and the new four-segmentswitching sequence is adopted to reduce the switching frequency.Simulation results show that the total harmonic distortiongrows down with the switching frequency decreasing,moreover,the algorithm runtime is also decreased.

A Space Vector Modulation Based Three-level PWM Rectifier under Simple Sliding Mode Control Strategy

In this paper, a voltage oriented control strategy for three-level PWM rectifier based on Sliding Mode Control (SMC) is introduced in order to obtain fast and accurate response of dc-bus voltage. To verify the validity of the analysis and the feasibility of the proposed control method a set of simulation tests have been conducted using Matlab/Simulink. The simulation results show that compared to the conventional PI controller, the SMC can reduce drastically the three-level rectifier’s voltage fluctuation and improve the dynamic response of dc-bus significantly.

A Modified Neutral-point Voltage Control Strategy for Three-level Inverters Based on Decomposition of Space Vector Diagram

Capacitor voltage imbalance is a significant problem for three-level inverters.Due to the mid-point modulation of these inverter topologies,the neutral point potential moves up or down depending on the neutral point current direction creating imbalanced voltages among the two capacitors.This imbalanced capacitor voltage causes imbalanced voltage stress among the semiconductor devices and causes increase output voltage and current harmonics.This paper introduces a modified voltage balancing strategy using two-level space vector modulation.By decomposing the three-level space vector diagram into two-level space vector diagram and redistributing the dwell times of the two-level zero space vectors,the modified voltage balancing method ensures minimal NP voltage ripple.Compared to the commonly used NP voltage control method(using 3L SVM[9]),the proposed modified NP voltage control method offers a slightly higher neutral-point voltage ripple and output voltage harmonics but,it has much lower switching loss,code size and execution time.

Model predictive flux control of permanent magnet synchronous motor driven by three-level inverter based on fine-division strategy

Aiming at the difficulty of setting the weight coefficient in the value function of model predictive torque control(MPTC)for permanent magnet synchronous motor(PMSM)driven by three-level inverter,a fine-division model predictive flux control(MPFC)method is proposed.First,establish a mathematical model between the motor torque and the stator flux linkage according to the mathematical equations of PMSM.Thus,the control of the motor torque and stator flux linkage in the MPTC is transformed into the control of a single stator flux linkage vector,omitting the cumbersome weight setting process in the traditional MPTC.The midpoint potential control strategy is proposed,which uses the characteristics of redundant small vectors to balance the midpoint potential.After that,a fine-division strategy is proposed,which effectively reduces the number of candidate vectors and the computational burden of the system.Finally,the proposed MPFC is compared with MPTC by simulation.The results show that the proposed fine-division MPFC effectively reduces the system calculation,and has the advantages of simple principle and better dynamic and steady-state control performance.The feasibility of the control strategy is verified.

Model predictive current control for PMSM driven by three-level inverter based on fractional sliding mode speed observer

Based on the fractional order theory and sliding mode control theory,a model prediction current control(MPCC)strategy based on fractional observer is proposed for the permanent magnet synchronous motor(PMSM)driven by three-level inverter.Compared with the traditional sliding mode speed observer,the observer is very simple and eases to implement.Moreover,the observer reduces the ripple of the motor speed in high frequency range in an efficient way.To reduce the stator current ripple and improve the control performance of the torque and speed,the MPCC strategy is put forward,which can make PMSM MPCC system have better control performance,stronger robustness and good dynamic performance.The simulation results validate the feasibility and effectiveness of the proposed scheme.

A Simple Scheme for Realizing a Multiqubit Controlled-Phase Gate Through a Resonant Interaction of Three-Level Atoms with a Single-Mode Cavity

A very simpJe theoretical scheme is proposed to implement two-and three-qubit controlled-phase gates firstly only using a single resonant interaction between ladder-type three-level atoms and the single-mode cavity. In the presented protocol, the quantum information is encoded on the stable ground states of the atoms （as the controlling qubits） and the zero- and one-photon Fock states of cavity-field （as the target qubit）. Under the influence of the atomic spontaneous emission, the decay of the cavity-mode, and deviation of the coupling strength, the three-qubit controlled- phase gate may have a comparatively high fidelity. The experimental feasibility of controlled-phase gate and the ease that is extended to realize N-qubit controlled-phase gate are also discussed.

Dynamics of a three-level V-type atom driven by a cavity photon and microwave field

We discuss the dynamics of a three-level V-type atom driven simultaneously by a cavity photon and microwave field by examining the atomic population evolution. Owing to the coupling effect of the cavity photon, periodical oscillation of the population between the two upper states and the ground state takes place, which is the well-known vacuum Rabi oscillation. Meanwhile, the population exchange between the upmost level and the middle level can occur due to the driving action of the external microwave field. The general dynamic behavior is the superposition of a fast and a slow periodical oscillation under the cooperative and competitive effect of the cavity photon and the microwave field. Numerical results demonstrate that the time evolution of the population is strongly dependent on the atom-cavity coupling coefficient g and Rabi frequency Ωe that reflects the intensity of the external microwave field. By modulating the two parameters g and Ωe, a large number of population transfer behaviors can be achieved.