非等同两原子与光场相互作用系统的腔场谱

研究了两个二能级原子与单模腔场具有不同耦合常量系统的腔场谱,讨论了量子化光场分别处于不同的光子数态时腔场谱结构随相对耦合常量R变化的新特性。发现随着R由0到1的增加,腔场谱各对应峰峰位相对腔场原共振频率ω0对称偏移;真空场（n=0）的峰高在0〈R〈0．3内变化较快,其拉比峰个数按2→6→4规律变化;弱场（n=1）峰高在0〈R〈0．5内变化较快,其峰数量按2→6→12→9→7规律变化;强场（n=8）峰高在0〈R〈0．1内改变迅速,其峰数量按2→8→11→5规律变化,谱结构显得更加复杂;进一步的计算表明,当n〉〉8时。其峰的数量按3→5→3规律变化。同时发现,R=0和R=1时,峰的数量相对较少。各峰峰高之和由最小单调增至最大,这在物理上反映了原子的协作效应。     

Effective Dynamics for Particles Coupled to a Quantized Scalar Field

We consider a system of N non-relativistic spinless quantum particles (“electrons”) interacting with a quantized scalar Bose field (whose excitations we call “photons”). We examine the case when the velocity v of the electrons is small with respect to the one of the photons, denoted by c (v/c = ε ≪ 1). We show that dressed particle states exist (particles surrounded by “virtual photons”), which, up to terms of order (v/c)³, follow Hamiltonian dynamics. The effective N-particle Hamiltonian contains the kinetic energies of the particles and Coulomb-like pair potentials at order (v/c)⁰ and the velocity dependent Darwin interaction and a mass renormalization at order (v/c)². Beyond that order the effective dynamics are expected to be dissipative. The main mathematical tool we use is adiabatic perturbation theory. However, in the present case there is no eigenvalue which is separated by a gap from the rest of the spectrum, but its role is taken by the bottom of the absolutely continuous spectrum, which is not an eigenvalue. Nevertheless we construct approximate dressed electron subspaces, which are adiabatically invariant for the dynamics up to order . We also give an explicit expression for the non-adiabatic transitions corresponding to emission of free photons. For the radiated energy we obtain the quantum analogue of the Larmor formula of classical electrodynamics.     

两耦合原子与双模二项式光场相互作用系统的腔场谱

研究了高Q腔中具有偶极相互作用的两个等同二能级原子与双模二项式光场相互作用过程的腔场谱,重点研究了两模腔场谱的干涉效应对谱结构的影响。结果表明:两模光场平均场强相等时,每模腔场谱一般出现对称多峰结构。随着初始场强的增加中间3峰趋于iω和ωi±0.7g处,而边峰消失。当两模初始场的频率差Δ大于6g(g为原子与腔场的耦合常量)时,两模间的干涉效应可以忽略;在Δ小于6g时,模间的干涉效应对腔场谱结构有明显的影响;尤其当Δ从1.4g逐渐减少时,模Ⅰ和模Ⅱ的三个主峰开始逐渐重叠,两模腔场谱之间出现了十分明显的干涉现象。     

Scott Correction for Large Atoms and Molecules in a Self-Generated Magnetic Field

We consider a large neutral molecule with total nuclear charge Z in non-relativistic quantum mechanics with a self-generated classical electromagnetic field. To ensure stability, we assume that Z α ² ≤ κ ₀ for a sufficiently small κ ₀, where α denotes the fine structure constant. We show that, in the simultaneous limit Z → ∞, α → 0 such that κ = Z α ² is fixed, the ground state energy of the system is given by a two term expansion c ₁ Z ^7/3 + c ₂(κ) Z ² + o(Z ²). The leading term is given by the non-magnetic Thomas-Fermi theory. Our result shows that the magnetic field affects only the second (so-called Scott) term in the expansion.     

热辐射场中两个耦合的二能级原子量子态的纠缠(英文)

两个偶极耦合的二能级原子置于热辐射场中,原子用泡利算符描述,环境用无穷的谐振子热库描述,运用密度矩阵方法,得到两能级原子密度矩阵元演化规律.针对三种不同的初始状态,利用共生纠缠度分析置于热辐射场中原子量子态的纠缠.结果表明:当两个原子初始处于不同量子叠加态时,原子的纠缠呈现出明显的差异.     

Magnetic Field Dependent Tunneling of Atoms and Molecules in Non-Magnetic Disordered Solids

The low-temperature properties of disordered solids, such as glasses or crystals with certain substitutional defects are governed by atomic tunneling systems. Until recently it was believed that the dielectric properties of insulating materials devoid of magnetic impurities should not—or only very weakly—depend on external magnetic fields. In contrast, new experiments on glasses and crystalline defect systems show a pronounced magnetic field dependence of the dielectric properties of such materials at ultra-low temperatures. In particular, the low-frequency dielectric susceptibility and the amplitude of polarization echoes appear to be strongly affected by magnetic fields. These very surprising findings clearly indicate that atomic tunneling systems can couple to magnetic fields. We summarize the available data and discuss the possible origin of these intriguing phenomena.     

Entanglement of Two Superconducting Charge Qubits Induced by Quantized Radiation Field

We consider two superconducting charge qubits coupled by a single-mode quantized field. We suppose that the two superconducting charge qubits be initially prepared in the mixed and separable state. As time evolves, we will investigate the entanglement between two superconducting charge qubits induced by the quantized field.     

耦合双原子与非线性相干态相互作用模型的腔场谱

研究了两个偶极 偶极相互作用的全同二能级原子与高Q腔内非线性相干态光场相互作用过程的腔场谱 .讨论了原子间耦合强度、初始场光子数分布和初始场强度的改变对光谱结构的影响.     

Radiation Properties of Systems of Three and Four Continuously Pumped Atoms

Radiation properties of three and four atoms continuously pumped by an incoherent excitation mechanism are investigated by using Lehmberg's master equation and the quantum fluctuation-regression theorem. For proper configurations we found in comparison with independent atoms simultaneously (i) an enlargement of the radiation rate, (ii) a spectral narrowing and (iii) a reduction of intensity fluctuations.     

Asymptotic Entanglement Sudden Death in Two Atoms with Dipole–Dipole and Ising Interactions Coupled to a Radiation Field at Non-Zero Detuning

We investigate the time evolution and asymptotic behavior of a system of two two-level atoms (qubits) interacting off-resonance with a single mode radiation field. The two atoms are coupled to each other through dipole–dipole as well as Ising interactions. An exact analytic solution for the system dynamics that spans the entire phase space is provided. We focus on initial states that cause the system to evolve to entanglement sudden death (ESD) between the two atoms. We find that combining the Ising and dipole–dipole interactions is very powerful in controlling the entanglement dynamics and ESD compared with either one of them separately. Their effects on eliminating ESD may add up constructively or destructively depending on the type of Ising interaction (Ferromagnetic or anti-Ferromagnetic), the detuning parameter value, and the initial state of the system. The asymptotic behavior of the ESD is found to depend substantially on the initial state of the system, where ESD can be entirely eliminated by tuning the system parameters except in the case of an initial correlated Bell state. Interestingly, the entanglement, atomic population and quantum correlation between the two atoms and the field synchronize and reach asymptotically quasi-steady dynamic states. Each one of them ends up as a continuous irregular oscillation, where the collapse periods vanish, with a limited amplitude and an approximately constant mean value that depend on the initial state and the system parameters choice. This indicates an asymptotic continuous exchange of energy (and strong quantum correlation) between the atoms and the field takes place, accompanied by diminished ESD for these chosen setups of the system. This system can be realized in spin states of quantum dots or Rydberg atoms in optical cavities, and superconducting or hybrid qubits in linear resonators.     

Multiphoton Processes of Two Modes of Quantized Field Interaction with Interacting Asymmetric Two Two-Level Atoms

International Journal of Theoretical Physics - The interaction between two modes quantized field and asymmetric two atoms represents one of the important quantum models to study the nonclassical...     

单模辐射场与N个原子相互作用理论

用玻色算符的三维型哈密顿量描述单模辐射场与Ｎ个两能级原子的相互作用。在原子系统处于低能态。光子数很大的初始条件下，得到了作用系统的动力学变化规律。     

压缩真空场与耦合双原子Raman相互作用系统场熵的演化特性

利用全量子理论,研究了压缩真空场与耦合双原子Raman相互作用系统的场熵演化特性,讨论了系统耦合常数和光场初始压缩因子对场熵演化特性的影响.结果表明,场熵的时间演化规律与原子布居差的时间演化规律非常相似.当原子间的偶极-偶极相互作用较弱时,场熵演化呈现周期性的崩塌与回复现象;当原子间的偶极-偶极相互作用较强时,场熵演化呈现不规则振荡,崩塌与回复周期现象消失.     

两个二能级原子与辐射场的量子动力学性质

用完全量子化方法研究两个二能级原子与腔场相互作用过程中，原子能级占居几率与辐射场的量子动力学性质，讨论了原子间耦合及激光发场对上述性质的影响，揭示了原子耦合与原子－场相互作用之间的联系。     

偏振光激发的Sr原子电偶极辐射

原子与激光场相互作用产生的自发辐射可以用经典电偶极辐射理论很好的描述.通过改变与Sr原子束相互作用激光的偏振方向,分析探测Sr原子束荧光强度的变化,测定了在远场区的电偶极辐射特性.Sr原子电偶极子在远场区辐射能量的空间方向分布满足sin2θ关系,利用这一规律可以有效地探测到最强的荧光光谱.     

Entanglement of Two Coupled Atoms in the Presence of a Time-Dependent External Magnetic Field

We study the problem of a time-dependent nonuniform magnetic field in the Heisenberg chain. We consider two cases: a single two-level atom and N-level atoms affecting by the magnetic field. We obtain the wave function and use it for calculating the expectation values of the dynamical operators, more precisely, the atomic inversion, in order to study the phenomena of revivals and collapses. Furthermore, we obtain the expectation value of other operators of the SU(2) group and discuss the phenomenon of squeezing. We show that the phase angle η and the detuning parameter δ are the most substantial parameters of the model under consideration.     

Entanglement Dynamics of Linear and Nonlinear Interaction of Two Two-Level Atoms with a Quantized Phase-Damped Field in the Dispersive Regime

In this paper we study the linear and nonlinear (intensity-dependent) interactions of two two-level atoms with a single-mode quantized field far from resonance, while the phase-damping effect is also taken into account. To find the analytical solution of the atom-field state vector corresponding to the considered model, after deducing the effective Hamiltonian we evaluate the time-dependent elements of the density operator using the master equation approach and superoperator method. Consequently, we are able to study the influences of the special nonlinearity function \(f (n) = \sqrt {n}\), the intensity of the initial coherent state field and the phase-damping parameter on the degree of entanglement of the whole system as well as the field and atom. It is shown that in the presence of damping, by passing time, the amount of entanglement of each subsystem with the rest of system, asymptotically reaches to its stationary and maximum value. Also, the nonlinear interaction does not have any effect on the entanglement of one of the atoms with the rest of system, but it changes the amplitude and time period of entanglement oscillations of the field and the other atom. Moreover, this may cause that, the degree of entanglement which may be low (high) at some moments of time becomes high (low) by entering the intensity-dependent function in the atom-field coupling.     

Entanglement of Two Atoms Induced by a Fock State of Radiation Field

Considering the intrinsic decoherence proposed by Milburn, we investigate the entanglement between two two-level atoms induced by a Fock state of single-mode quantized radiation field. The time-dependent reduced density matrix of the atoms system is given explicitly. Due to the intrinsic decoherence, the atoms system will approach a stationary state, where the stationary entanglement depends on the initial states of the field and the atoms.