Yangian代数在混合介子态的纠缠和衰变中的应用

Yangian代数是超出李代数更大的无穷维代数,是研究非线性量子完全可积系统的新对称特性的有力数学工具.基于介子态中夸克-味su(3)对称性和Yangian代数生成元的跃迁特性,本文研究了Yangian代数Y(su(3))生成元在三种正反介子态(π~±,K~±,K~0和K~0)各自组成的三种混合介子态(π,K和K_i~0)衰变中的作用.将Y(su(3))代数的八个生成元(I~±,U~±,V~±,I~3和I~8)作为跃迁算子,作用在混合介子态上,研究其可能的衰变道,以及衰变前后纠缠度的变化.结果表明:1)在李代数范围内的生成元I~3和I~8作用下,三种混合介子态衰变后组成成分没有发生变化,其中混合介子态π在I~8作用下衰变前后纠缠无变化,其他衰变纠缠度发生了变化;2)在其他的六个(I~±,U~±和V~±)超出李代数的生成元的作用下,三种混合介子态衰变前后组成成分发生了变化,其中两个衰变后变成单态,纠缠度为零;两个衰变不存在;剩余两个衰变后纠缠度发生了变化,此外在带电(K)和中性(K_I~0)两类K型混合介子态的六种可能的衰变中,两种类型的末态的纠缠度两两相同;3)三种混合介子态之间可以通过I~±,U~±和V~±算子循环转化,具有明显的对称性.本文从具有的对称性上提供了一种探索混合介子态可能衰变的方法,并且可以用此方法去预测可能的未知衰变粒子和解释己测得的衰变问题.     

Remark on state vector construction when flavor mixing exists

In the framework of quantum field theory, we consider the way to construct the one-particle state (with definite 3-momentum) when particle mixing exists, such as in the case of flavor-neutrino mixing. In the preceding report (Prog. Theor. Phys. 112, 901 (2004)), we have examined the structure of expectation values of the flavor neutrino charges (at time t) with respect to a neutrino-source state prepared at time t′ (earlier than t). When there is no mixing, each of various contributions to the expectation value is equal, in its dominant part, to the transition probability corresponding to the respective neutrino-production process. On the basis of the assumption that such an equality holds also in the mixing case, we can find an appropriate form of one-flavor-neutrino state with 3-momentum and helicity. Along the same way, we examine the boson case when flavor mixing exists. We give remarks on the relation and difference between the ordinary and the present approaches to flavor oscillation. The text was submitted by the authors in English.     

Teleportation of a two-atom entangled state via cavity decay

This paper proposes a scheme for teleporting a two-atom entangled state using leaky cavities. It uses resonant atom--cavity interaction to map the atomic state onto the cavity field. Then it utilizes the interference of polarized photons to establish the correlation between the distant sender and receiver. The advantage of the scheme is that the fidelity is independent of the cavity decay rate, atomic decay and detection efficiency.     

Inhomogeneous quantum diffusion and decay of a meta-stable state

We consider the quantum stochastic dynamics of a system whose interaction with the reservoir is considered to be linear in bath co-ordinates but nonlinear in system co-ordinates. The role of the space-dependent friction and diffusion has been examined in the decay rate of a particle from a meta-stable well. We show how the decay rate can be hindered by inhomogeneous dissipation due to nonlinear system–bath coupling strength.     

Theory of the decay process of metastable state

The short-time and long-time behavior of the distribution function P(x, t) are investigated in the laser model by using the generating function $\text{G(α,}\text{β}\text{;t) = σ(α-y(t)) Π}{}^{\mathrm{\infty }}{}_{\mathrm{n=2}}\text{σ(β}{}_{\mathrm{n}}\text{- M}{}_{\mathrm{n}}\text{(t)),}\text{where}\text{y(t)  ?xP(x, t)}\text{d}\text{x}\text{and}\text{M}{}_{\mathrm{n}}\text{(t)  ?(x - y(t))}{}^{\mathrm{n}}\text{P(x,t)}\text{d}\text{x}$.     

Clusters on the basis of bright multimode light in a mixed state

The possibility of cluster-state generation on the basis of mixing radiation from two independent lasers in an asymmetric Mach–Zehnder interferometer is shown in this paper. The formulation of the problem is close to that considered before by Menicucci (Phys. Rev. A 83, 62314 (2011)) and Yokouama et al. (Nature Photonics 7, 982 (2013)). The specificity of the current consideration is that our sources of squeezed light (phase-locked sub-Poissonian lasers) radiate bright light in a mixed state, in contrast to an optical parametric oscillator in the subthreshold mode. We also take into account the multimode structure of the radiation, not restricting ourselves to only a constant component of the field-noise characteristics. To set the cluster state, the van Loock–Furusawa separability criterion is used.     

Quantum interferometry via a coherent state mixed with a squeezed number state

We theoretically investigate the phase sensitivity with parity measurement on a Mach–Zehnder interferometer with a coherent state combined with a squeezed number state. Within a constraint on the total mean photon number, we find, via parity measurement, that the mixing of a coherent state and squeezed number state can give better phase sensitivity than mixing a coherent state and squeezed vacuum state when the phase shift deviates from the optimal phase φ= 0. In addition,we show that the classical Fisher information for parity measurement saturates the quantum Fisher information when the phase shift approaches to zero. Thus, the quantum Crame′r–Rao bound can be reached via the parity measurement in the case of φ= 0.     

Surface induced mixed state of a superconducting film

Presented in this paper is a theoretical analysis of a planar surface induced mixed state for a superconducting film in parallel applied field. An analytical solution of the internal magnetic field is obtained based on Saint-James and de Gennes' order parameter in a film. An expression of Gibbs free energy per unit volume without restriction of a geometry is derived from non-linear Ginzburg-Landau (GL) equation in terms of a renormalized GL parameter and a modified geometric factor. Based on the Gibbs free energy, a phase diagram of distinguishing a first and second order phase transition for a type I superconducting film is calculated. The numerical results for exact solutions of spatial variation of order parameter, current density and internal magnetic field in the film geometry in parallel applied field case are presented. Near the upper critical field, the first entry of an applied field in the film exhibits a laminar structure.     

Radiative decay of the metastable quartet state of copperporphin

In CuP the low temperature luminescence originates from eight transitions between a quartet (M = ±3/2, ±1/2) and a doublet (M′ = ±1/2) with M and M′ denoting the (approximate) eigenvalues of the spin angular momentum S_z along the fourfold axis. Here we report (1) the selection rules governing the polarizations of the transitions; (2) the zero-field splitting ξ between the ±3/2 and ±1/2 components of the quartet for CuP in an n-octane crystal (ξ = 1·1 ± 0·2 cm^-1); (3) a photo-selection experiment on CuP in an isopentane glass from which it is concluded that the ratio of in-plane to out-of-plane polarization in the 0-0 band at 2·1 K amounts to an intensity ratio I _‖/I _⊥ ≈ 2. The implications of these results for the different SOC pathways are analysed.     

Environment-induced decay of teleportation fidelity of the one-qubit state

The one-qubit teleportation protocol is reexamined when it is executed in the presence of various decohering environments. The results revealed that this quantum protocol is more robust under the influence of dephasing environment than those under the influence of dissipative or noisy environment. The environment may deprive the quantum advantage of teleportation over purely classical communication in a finite or infinite lifetime, which is dependent on the type of environment. Also we found that except entanglement, the purity of the entangled state resource is also crucial in determining the quality of the teleported state.     

Intramolecular excited state charge transfer and fluorescence decay of p-Cyano-N,N-dimethylaniline in mixed hydrocarbon/halocarbon solvents

Fluorescence spectra, quantum yields and lifetimes of p-cyano-N,N-dimethylaniline (CDMA) were studied in various binary mixtures of n-hexane with chlorinated hydrocarbons. Solvent effects on the equilibrium between normal emission and fluorescence originating from the highly dipolar twisted internal charge transfer (TICT) state arise predominantly from non-specific solute-solvent interactions. The non-radiative deactivation rate of the TICT state is affected primarily by the solvent composition and slows down with the stabilization of the TICT state in environments of high polarity.     

On the decay width of multiply measured unstable state

In the case of multiple measurements we have found that there is nonzero decay width () (even for bound states) and that, for relatively long time intervals separating successive measurements, () tends like ^–k (k 1 according to the investigated model) to the asymptotic value _o for unstable states and to zero for bound states. We have shown that the detector efficiencyZ 1 is responsible for this effect and that the evolution operator acting in the considered subspace of states should be renormalized to avoid this effect. As an illustration we have considered electromagnetic levels in the Coulomb field as an example of unstable states.     

Competition between relaxation and decay of a resonantly excited core-hole state

By a many-body theory it is shown that in general when the time scale of the relaxation from the resonantly excited core-hole state to the fully relaxed core-hole state is much shorter than that of core-hole decay, the autoionization (deexcitation) spectrum is more or less identical to the Auger-electron spectrum by core-hole decay of the fully relaxed core-hole state. Here, the fully relaxed core-hole state is the lowest core-hole state in the X-ray photoelectron spectroscopy spectrum. The present theory explains why the C 1s autoionization spectrum of CO molecule adsorbed on Ni(1 0 0) surface measured at the resonant core-level electron excitation energy is more or less indentical to the Auger-electron spectrum measured at far above the core-level electron ionization limit.     

Remark on the energy spectrum of a decaying system

Some time-evolution operators of a general unstable system lead to unphysical spectrum (unbounded below) of the total Hamiltonian. Various necessary conditions for boundeness of the spectrum are known. It is shown here, how this spectrum can be determined, which, in particular, gives the sufficient condition.