Dynamics of vacuum excitations and quark confinement in quantum field theories

A unified approach to interacting vacuum excitations and quark confinement is formulated in quantum field theories with symmetry breakdown. Vacuum excitations are shown to be coherent clouds of Goldstone bosons or gauge bosons and are interpreted as new asymptotic extended particle states. They correspond to all dynamically possible space-time dependent Bose condensations of the Goldstone bosons in a given theory. Different configurations of vacuum excitations are connected to one another by a family of invariant boson transformations. As an example, the Nambu theory of interacting vortex strings is derived from a Nambu-Heisenberg quark-gluon field theory. The quarks can be completely confined to the strings while the gluons cluster in quantized magnetic flux bundles of penetration width m_v^?1 and provide a short range interaction force.     

Photon Excitations Excitated the Sqeezing Properties of the Excited Entangled Coherent States

In our previous paper, we have introduced a new kind of continuous-variable-type entangled states, called double-mode excited entangled coherent states. In this paper, we study sum squeezing properties of such excited entangled coherent states. We focus on discussing the influence of photon excitations on sum squeezing properties. It is found that the photon excitations seriously affected sqeezing properties of the excited entangled coherent states. With increasing the number of the photon excitations m, the higher-order terms move away from its initial state |ψ ₀〉 and the degrees of sum squeezing are increasing. In this sense, it implies that the photon excitations excitated the sum sqeezing properties of the double-mode excited entangled coherent states.     

非简并拉曼过程中交流斯塔克位移对腔场谱的影响

研究了原子与双模光场非简并拉曼耦合过程中交流斯塔克位移对腔场谱的影响.给出了原子处于基态且双模初始场为光子数态、相干态和压缩真空态时光谱结构的数值结果.发现数态光场在弱场条件下每模腔场谱都是三峰结构，在强场条件下则为双峰或单峰结构，相干态和压缩真空态光场的腔场谱在弱场或强场条件下都是双峰结构.随着斯塔克位移参数的变化,双峰的高度此长彼消. 关键词： 交流斯塔克位移 非简并拉曼过程 腔场谱     

Entanglement dynamics in Coriolis coupled rovibrational states of formaldehyde

The entanglement dynamics of two vibrational modes of a polyatomic molecule coupled by Coriolis interaction to overall molecular rotation is studied in terms of two negativities, N(t) and N_s(t), respectively, defined by the minimum of the eigenvalues and by the sum of the negative eigenvalues of the partial transpose of a density matrix. Various initial states are the products of Dicke states and the products of coherent states of vibrations and rotations. Formaldehyde is taken as an example, and the von Neumann entropy s(t) is simulated for the comparison with both negativities. It is shown that negativity N_s(t) is positively correlated with entropy s(t), and the correlated behavior between negativity N(t) and entropy s(t) strongly depends on initial states. However, these three indicators of entanglement display a dominantly positive correlation for the coherent states with small or large parameters. In addition, for the latter state two quantities N(t) and s(t) are nearly unchanged for a long time. This time can be further increased by the increasing of vibrational quantum number so that molecular information processing and quantum computing is allowed. These results are useful in quantum information theory.     

Modulation spectroscopy using the beam-foil light source

When a beam of ions passes through a thin exciter foil, certain radiation emitted by the beam particles can exhibit time-periodic intensity variations. These variations can be induced by external E and H fields, or they can be the result of the field-free atomic structure itself.Intensity modulations observed so far in beam-foil spectroscopy can be divided into three classes: (1) Quantum mechanical interference of fine structure levels. This is a QM resonance arising from time-dependent populations of emitting states having different transition probabilities. The resonance is induced by external constant electric fields. (2) Initial coherent superpositions of radiating states. This results from the creation of M_L alignment at the instant of excitation by the foil. The modulations are field free and are observed in polarized light. (3) Rotating electric dipole in a magnetic field. When alignment occurs, the intensity of the beam radiation after excitation satisfies the relation I(t) = = I₀[1+Acos(2γHt)] e^?αt. The modulation will be a function of the magnetic field H and the gyromagnetic ratio γ.These effects can be used to study Lamb shifts, g-values, fine structure levels, and interaction processes.     

Single-mode photon number measurement for the squeezed two-mode number state

Based on the fact that a two-mode squeezed number state is a two-variable Hermite polynomial excitation of the two-mode squeezed vacuum state, the result of one-mode l-photon measurement for the two-mode squeezed number state $S_2|m,n\rangle$ is discussed. It is found that a remaining field-mode simultaneously collapses into a number state $|n-m+l\rangle$ with the coefficient being a Jacobi polynomial of n, m and l, which manifestly exhibits the entanglement between the two modes, i.e. it depends on the number-difference between the two modes. The second mode collapses into an excited coherent state when the first mode is measured as a coherent state.     

Inducing and destruction of chimeras and chimera-like states by an external harmonic force

We study the phenomena of chimera destruction and inducing of chimera-like states in an ensemble of nonlocally coupled chaotic Rössler oscillators under an external harmonic force. The localized harmonic influence can lead to both destruction and changing of the spatial topology of chimeras. At the same time this influence can cause the emergence of stable chimera-like states (induced chimeras) for the regime of partial coherent chaos. Induced chimeras are also observed for the global influence. We show the possibility of controlling the chimera-like state topology by varying the parameters of localized external harmonic influence.     

激发纠缠相干态的统计性质

将玻色湮灭算符的逆算符作用在纠缠相干态的一个模上得到激发纠缠相干态.该量子态是玻色湮灭算符的偶次幂本征态;由于两个场模间的纠缠,在a模上增加光子不但可以使a模的平均光子数增加,也可以使b模的平均光子数发生变化;当a模上增加光子后,两个场模的亚泊松分布特性和Cauchy-Schwartz不等式的破坏都得到了增强,但模间反关联度反而减弱.     

Formation of correlated states and tunneling for a low energy and controlled pulsed action on particles

We consider a method for optimizing the tunnel effect for low-energy particles by using coherent correlated states formed under controllable pulsed action on these particles. Typical examples of such actions are the effect of a pulsed magnetic field on charged particles in a gas or plasma. Coherent correlated states are characterized most comprehensively by the correlation coefficient r(t); an increase of this factor elevates the probability of particle tunneling through a high potential barrier by several orders of magnitude without an appreciable increase in their energy. It is shown for the first time that the formation of coherent correlated states, as well as maximal |r(t)|_max and time-averaged 〈|r(t)|〉 amplitudes of the correlation coefficient and the corresponding tunneling probability are characterized by a nonmonotonic (oscillating) dependence on the forming pulse duration and amplitude. This result makes it possible to optimize experiments on the realization of low-energy nuclear fusion and demonstrates the incorrectness of the intuitive idea that the tunneling probability always increases with the amplitude of an external action on a particle. Our conclusions can be used, in particular, for explaining random (unpredictable and low-repeatability) experimental results on optimization of energy release from nuclear reactions occurring under a pulsed action with fluctuations of the amplitude and duration. We also consider physical premises for the observed dependences and obtain optimal relations between the aforementioned parameters, which ensure the formation of an optimal coherent correlated state and optimal low-energy tunneling in various physical systems with allowance for the dephasing action of a random force. The results of theoretical analysis are compared with the data of successful experiments on the generation of neutrons and alpha particles in an electric discharge in air and gaseous deuterium.     

Strong selective excitation of Raman-active vibrations and energy transfer between low-lying vibrational states of a CO2 molecule studied by PARS and CARS

We experimentally demonstrate the novel technique of inducing the highly nonequilibrium distribution of molecules over vibrational states by two-frequency coherent Raman excitation. The technique can be used for selective excitation of totally symmetric and other Raman-active molecular transitions. Two counter propagating focused laser beams (second harmonic of Nd: YAG and dye laser) were used to induce population difference changes at the 00⁰0–10⁰0 transition in CO₂ molecules. The excitation and relaxation kinetics of this and neighbours vibrational modes of CO₂ were studied both by CARS and PARS. Vibrational excitation of up to 20% of the total number of irradiated molecules is measured; previously unknown desactivation constant of CO₂ (10⁰0) and CO₂ (02⁰0) states via CO₂ (01¹0) state is estimated to be K = (3±1) × 1 ⁵s^-1torr^-1.     

Electric field induced anomalies in frequency shift and collisional perturbations in the 5snd D2 Rydberg series of strontium in a heatpipe setup with ionization detection

We have examined the effect of weak DC electric field (2-20 V/cm) complimented by foreign gas collisions on the bound J = 2 even-parity 5snd ¹D₂ Rydberg states of neutral strontium. We use resonant two-photon transverse excitation, employing a narrow bandwidth tunable dye laser and an atomic jet in a heatpipe setup with ionization detection. In this paper we report certain anomalies in the observed spectra covering principal quantum number range n = 27-42 indicating a frequency shift reversal with nearly quadratic dependence on the field strength above an anti-resonance region. Furthermore, we have observed the emergence of highly localized doubly-excited 4d² states, including a remarkably broad perturber with large angular momentum, uncovering orbital contraction effect. This non-Rydberg excitation, which intrudes upon the two-photon spectrum with large energy overlap is due to single-photon excitations from the 5s5p ¹P₁ resonance level following molecular dissociation of the Sr₂ dimers suitably governed by binary atomic collisions. Our study which involves laser excitation complimented by electric field and collisions using inexpensive home-made setup opens up the possibilities for a new class of experiments, with considerable simplicity in the choice of excitation schemes for both Rydberg and non-Rydberg transitions, to reach states lying at high energies which cannot otherwise be accessed from the ground state due to parity and selection rules, while allowing one to probe localization properties of atomic wave functions.     

Coherent crystallization of bismuth under strong excitation by ultrashort laser pulses

By means of coherent control, fully symmetric bismuth phonons A _1og are investigated at helium temperature depending on the degree of crystal excitation. It is shown that coherent phonons with large amplitude show phase rigidity that is absent at small amplitude. Such a change in the phase properties of crystal lattice excitations can be understood using the concept of a coherent crystal, the achievement of which results from condensation of phonon modes arising with increasing degree of excitation.     

Observation of coherent phonon states in porous silicon films

The dynamics of differential transmission and reflectance spectra of porous silicon films was studied using the femtosecond excitation technique (τ≈50 fs, ?ω_pump=2.34 eV) with supercontinuum probing (?ω_probe=1.6–3.2 eV) and controlled time delay with a step of Δt=7 fs between the pump and probe pulses. A short-lived region of photoinduced bleaching was observed in the differential transmission spectra at wavelengths shorter than the pump wavelength. The excitation of coherent phonon states with a spectrum corresponding to nanocrystalline silicon with an admixture of a disordered phase was observed. The relaxation of electronic excitation was found to slow down in the spectral region where the amplitude of excited coherent vibrations was maximal.     

Kolmogorov turbulence, Anderson localization and KAM integrability

A modified Shastry-Sutherland model with fourth-nearest-neighbor dimerization is studied with strong coupling perturbation theory. One-triplet excitations are calculated up to the second order. Bose-Einstein condensation of one-triplet excitations may induce different ordered states, i.e. collinear antiferromagnetic state, Néel state or incommensurate state when the gap closes by changing the physical parameters or by an external magnetic field. Two-triplet bound states in the S = 1 and S = 2 channels are shown to exist around the symmetric lines of K _x = ±K _y and K _x ± K _y = ±??. For ferromagnetic dimer-dimer interaction, the energies of the bound states in the S = 1 (S = 2) channel lie above (below) the two-triplet continuum. By calculating the existence region, the degeneracy, the symmetry and the dispersion relation, a whole image and main features of the bound states are obtained. Experimental results of (CuX)LaNb₂O₇ with X = Cl, Br are interpreted.     

Condensate of excited states in magnesium

The results of theoretical study of the condensate of excited states in magnesium are reported. Excitations are described in the framework of the Hartree-Fock method taking into account energy level widths. It is shown that conditions for the emergence of condensed excited states are created in the optical range of atomic excitation energies. In the Mg₂ system, such conditions are created for any (indefinitely small) excitation fields in the optical energy range. The weaker the external field, the longer the lifetime and the shallower the potential well for the condensate of excitations. Most stable excitations in Mg₂ were detected at atomic spacings on the order of 9 Bohr radii.     

Variance squeezing and information entropy squeezing via Bloch coherent states in two-level nonlinear spin models

The nonclassical squeezing effect emerging from a nonlinear coupling model (generalized Jaynes–Cummings model) of a two-level atom interacting resonantly with a bimodal cavity field via two-photon transitions is investigated in the rotating wave approximation. Various Bloch coherent initial states (rotated states) for the atomic system are assumed, i.e., (i) ground state, (ii) excited state, and (iii) linear superposition of both states. Initially, the atomic system and the field are in a disentangled state, where the field modes are in Glauber coherent states via Poisson distribution. The model is numerically tested against simulations of time evolution of the based Heisenberg uncertainty relation variance and Shannon information entropy squeezing factors. The quantum state purity is computed for the three possible initial states and used as a criterion to get information about the entanglement of the components of the system. Analytical expression of the total density operator matrix elements at t > 0 shows, in fact, the present nonlinear model to be strongly entangled, where each of the definite initial Bloch coherent states is reduced to statistical mixtures. Thus, the present model does not preserve the modulus of the Bloch vector.     

Minimum-uncertainty states of systems with many degrees of freedom

The minimum-uncertainty states for systems with many degrees of freedom are investigated. The limiting situation, relevant to the electromagnetic field, is discussed and it is pointed out that the states that minimize Δp Δq do not tend to the coherent states. These latter, including the vacuum state, are minimum-uncertainty states for the transverse electric and magnetic fields. In an appendix a direct method to obtain the wave functional for the vacuum is presented.     

Stripe-like topological excitations in a two-dimensional Heisenberg ferromagnet

For a two-dimensional Heisenberg ferromagnet, a class of steady-state nonlinear excitations above the ground state is considered. The excitations have the form of stripes and exhibit quasiparticle properties. The effect of an external magnetic field on the basic characteristics of these nonlinear topological excitations is investigated. The magnetic field is found to destroy the instanton-type solutions (kinks) and to generate new particles with the properties of vortex-antivortex pairs: each particle has a zero topological charge and an energy close to the double skyrmion energy 8πJS². The dispersion of the quasiparticles and the dependences of their energy and momentum on the number of magnons localized by one excitation are discussed.     

Improving and Controlling Quantum Entanglement from Excited Barut–Girardello Coherent States via Unitary Beam Splitters

We construct the photon-added deformed Barut–Girardello coherent states (PA-DBGCSs) for bosonic fields by discussing the Klauder minimal set of conditions required to obtain coherent states. Using this set of deformed states, we propose a useful way to generate and control the entanglement generated via unitary beam splitters for different field amplitudes Z, deformation q, and excitation number m. Therefore, we provide the possibility to create highly entangled states. Moreover, we obtain the condition for maximum and separable output beam state. Finally, we examine the statistical properties of PA-DBGCSs, in view of the Mandel parameter, and exploit a connection between this quantity and variations in the behavior of the output-state entanglement. Our result can open new prospectives in different tasks of quantum information processing.     

Correlated states and transparency of a barrier for low-energy particles at monotonic deformation of a potential well with dissipation and a stochastic force

The features of the formation of correlated coherent states of a particle in a parabolic potential well at its monotonic deformation (expansion or compression) in finite limits have been considered in the presence of dissipation and a stochastic force. It has been shown that, in both deformation regimes, a correlated coherent state is rapidly formed with a large correlation coefficient |r| → 1, which corresponds at a low energy of the particle to a very significant (by a factor of 10⁵⁰–10¹⁰⁰ or larger) increase in the transparency of the potential barrier at its interaction with atoms (nuclei) forming the “walls” of the potential well or other atoms located in the same well. The efficiency of the formation of correlated coherent states, as well as |r|, increases with an increase in the deformation interval and with a decrease in the deformation time. The presence of the stochastic force acting on the particle can significantly reduce the maximum |r| value and result in the fast relaxation of correlated coherent states with |r| → 0. The effect of dissipation in real systems is weaker than the action of the stochastic force. It has been shown that the formation of correlated coherent states at the fast expansion of the well can underlie the mechanism of nuclear reactions at a low energy, e.g., in microcracks developing in the bulk of metal hydrides loaded with hydrogen or deuterium, as well as in a low-pressure plasma in a variable magnetic field in which the motion of ions is similar to a harmonic oscillator with a variable frequency.