Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质

研究了Ξ型三能级原子玻色-爱因斯坦凝聚体单模光场系统中双模原子激光的压缩性质.结果表明:双模原子激光能被周期性压缩,并且具有量子Rabi振荡和崩塌-回复现象两种形式的振荡.最大压缩深度和崩塌-回复振荡频率主要依赖于光场与原子间相互作用强度,量子Rabi振荡频率主要由光场圆频率决定.     

非旋波近似下光场与V型三能级原子依赖强度耦合作用系统中的光场压缩

利用全量子理论,研究了非旋波近似下单模光场与V型三能级原子依赖强度耦合的相互作用系统中光场的压缩效应.结果表明:光场的压缩依赖于系统的本身性质,而虚光子过程使光场的压缩程度明显加强并产生量子噪声,其大小依赖于初始场平均光子数n和光场频率ω,且与原子光场耦合强度g有关.     

超强耦合电路量子电动力学系统中反旋波效应对量子比特频率移动的影响

从实验上研究了四结磁通量子比特与多模共面波导谐振腔构成的超强耦合电路量子电动力学系统.通过传输谱测量和数值拟合,确定量子比特与腔第一模式的耦合强度已达到0.1倍谐振腔频率,进入了超强耦合区域;通过色散读出方法得到了系统的能谱,并通过增加探测场光子,从能谱上得到了量子比特频率随探测光子的位移.这种位移不仅包含旋波项的贡献,也包含了反旋波项的显著贡献,证实我们所实现的超强耦合系统是一个良好的研究量子拉比模型的实验平台,它在量子技术的诸多方面有潜在的应用,如量子模拟、超快量子逻辑门、纠缠态制备、量子比特保护等.     

虚光场效应对原子激光压缩性质的影响

在压缩真空态光场和二能级原子玻色-爱因斯坦凝聚体相互作用系统中, 应用全量子理论, 分别在旋波近似和非旋波近似下, 研究了原子激光的压缩特性以及原子本征频率、光场-原子的耦合系数、光场初始压缩因子以及虚光场对原子激光压缩特性的影响. 研究表明,原子激光的两个正交分量均可被周期性压缩,原子的本征频率决定了原子激光两个正交分量涨落的量子Rabi频率,光场与原子的耦合系数决定了原子激光正交分量涨落的崩塌-回复振荡频率,当光场初始压缩因子增大和考虑虚光场效应时,原子激光正交分量的压缩深度均加深. 关键词： 玻色-爱因斯坦凝聚 压缩真空态 原子激光 虚光场效应     

二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统中原子激光的压缩性质

利用格子液体方法对二能级原子玻色-爱因斯坦凝聚体与双模光场相互作用系统的哈密顿量进行了改进,并且研究了系统中原子激光的压缩性质.结果表明:原子激光的两个正交分量均可被周期性压缩,其最大压缩深度主要依赖于光场初始压缩因子,而崩塌-回复振荡频率和量子Rabi振荡频率主要分别由光场与原子间的相互作用强度和光场圆频率决定.     

非旋波近似下压缩真空场与三能级原子依赖强度耦合系统的光场压缩

利用全量子理论,研究了非旋波近似下压缩真空场与V型三能级原子依赖强度耦合相互作用系统中光场的压缩效应.数值计算结果表明:光场呈现出周期性压缩现象,而虚光子过程则对光场的压缩具有抑制作用并产生量子噪声,量子噪声大小依赖于光场的初始压缩因子r和光场频率ω,且与原子-光场耦合强度g有关.随着r的增大,虚光子过程对光场压缩抑制作用程度由弱到强再由强到弱;随着ω和g的增大,量子噪声分别减小和增大.     

双模SU(1,1)相干态光场与V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中光场的压缩特性

在双模SU(1,1)相干态光场和V-型三能级原子玻色-爱因斯坦凝聚体相互作用系统中,应用全量子理论,在旋波近似下,研究了双模光场的压缩特性,分别讨论了光场与原子之间的耦合常数、原子之间的相互作用和光场参数对光场压缩特性的影响.研究表明,光场的两个正交分量均被周期性压缩,光场与原子的耦合系数和原子间的相互作用强度增大时均使得光场正交分量涨落的周期缩短;光场参数的变化不影响光场压缩的周期,对压缩深度有一定的影响.     

非旋波近似下两纠缠原子的纠缠特性

采用了相干态正交化法研究了耦合强度以及偶极相互作用对Tavis-Cummings模型中两原子的纠缠的影响.与旋波近似比较发现,在弱耦合强度下,非旋波近似下两原子间的纠缠与旋波近似下的结果符合得很好,在强耦合区,原子之间的纠缠出现了突然死亡现象.研究同时发现耦合强度越大,原子间处于可分离态的时间越长,表明了原子间处于退纠缠的时间的长短是依赖于原子-光场的耦合强度的.而考虑了偶极相互作用时,随着偶极-偶极相互作用的加强,原子间的纠缠也将被加强.     

非旋波近似下两纠缠原子的纠缠特性

采用了相干态正交化法研究了耦合强度以及偶极相互作用对Tavis-Cummings模型中两原子的纠缠的影响.与旋波近似比较发现,在弱耦合强度下,非旋波近似下两原子间的纠缠与旋波近似下的结果符合得很好,在强耦合区,原子之间的纠缠出现了突然死亡现象.研究同时发现耦合强度越大,原子间处于可分离态的时间越长,表明了原子间处于退纠缠的时间的长短是依赖于原子-光场的耦合强度的.而考虑了偶极相互作用时,随着偶极-偶极相互作用的加强,原子间的纠缠也将被加强.     

Kerr介质中耦合V型三能级原子与相干态光场作用场的量子性质

研究了Kerr介质中相干态光场与耦合V型三能级原子相互作用过程中场的量子性质.利用量子光学中光场与原子相互作用的耦合Tavis-Cummings模型,对系统的动力学过程进行了求解.讨论了系统初始状态、失谐量、原子间偶极相互作用强度及Kerr系数对光场量子性质随时间演化的影响.数值计算结果表明:初态中场的平均光子数比较小时,光场能够展现出明显的量子效应|初始时刻原子激发态概率幅从小变大时,光场的反聚束效应变得越明显,而光场的压缩深度会先增大后减小|失谐量的变化对场的量子性质的影响不大,只是改变光场二阶相关函数和压缩参量振荡的周期|原子间耦合强度的增大使光场的反聚束效应减弱和光场的压缩深度变浅|Kerr系数的增大会增强光场的反聚束效应,而使光场的压缩深度变浅.     

Multiphoton dynamics of qutrits in the ultrastrong coupling regime with a quantized photonic field

Multiphoton resonant excitation of a three-state quantum system (a qutrit) with a single-mode photonic field is considered in the ultrastrong coupling regime, when the qutrit–photonic field coupling rate is comparable to appreciable fractions of the photon frequency. For ultrastrong couplings, the obtained solutions of the Schrödinger equation that reveal multiphoton Rabi oscillations in qutrits with the interference effects leading to the collapse and revival of atomic excitation probabilities at the direct multiphoton resonant transitions.     

Ultrastrong coupling regime and plasmon polaritons in parabolic semiconductor quantum wells

Ultrastrong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron interaction compensates the depolarization shift. As a result, a very large ratio of 27% of the Rabi frequency to the center resonance frequency as well as a polariton gap of width 2π × 670 GHz are observed, suggesting parabolic quantum wells as the system of choice in order to explore the ultrastrong coupling regime.     

Entanglement Dynamics of Two Qubits Coupled Independently to Cavities in the Ultrastrong Coupling Regime:Analytical Results

Dynamics of quantum entanglement of two qubits in two identical quantum Rabi models is studied analytically in the framework of corrections to the rotating-wave approximations.A closed-form expression for the entanglement dynamics initiated from the well-known Bell states is derived,which is very close to the numerical exact results up to the ultrastrong coupling regime.It is found that the vanishing entanglement can be purely induced by the counter-rotating terms,and can be enhanced with the atom-cavity coupling.     

Squeezing‐Enhanced Atom–Cavity Interaction in Coupled Cavities with High Dissipation Rates

The realization of the strong coupling regime is requisite for implementing quantum information tasks. Here, a method for enhancing the atom–field coupling in highly dissipative coupled cavities is proposed. By introducing parametric squeezing into the primary cavity, which is only virtually excited under specific parametric conditions, coupling enhancement between the atom and the auxiliary cavity is realized for appropriate squeezing parameters. This enables the system to be robust against large cavity decay and atomic spontaneous emission. The observation of vacuum Rabi oscillations show that the originally weakly coupled system can be enhanced into an effective strong coupling regime.     

虚光子过程对光场压缩效应的影响

本文利用非相对论量子电动力学理论,研究了双光子Jaynes-Cummings模型中非旋波项对光场压缩效应的影响,证明了光场压缩效应因虚光场效应而增强,并分析了压缩程度与光场的频率、强度及光场-原子耦合常数的关系。 关键词：     

Study of Some Properties of Two-Level Atom in Quantum Optics

With the concept of negative photon and the K-photon J C model, we investigate analytically the effect of virtual photon field on the collapse revival effect of atomic inversion and squeezing of atom, we find that there is a significant effect of virtual photon field on atomic inversion and squeezing of atom; with the one-photon model as an example, we find that the squeezing of atom occurs periodically, the time and times of squeezing are only related to the resonance frequency and the amplitude of squeezing related to coupling constant of atom field, mean photon number and resonance frequency; also we show that the effect of squeezing of atom does not exist within rotating wave approximation if K≥3. Taking the approach of nearest-neighboring spectrum in the quantum chaos field, we investigate the properties of energy spectrum in one-photon JC model and show that the integrable region,non-integrable region and transition region of this system can be illustrated by a phase diagram;also we discuss the influence of interaction of atoms on spectrum and Δ₃ statistics of adjacent energy levels, we find that the influence of interaction is little obvious in strong field but takes great important role in weak field.     

Potentialities of GaN-based microcavities in strong coupling regime at room temperature

In a recent publication [N. Antoine-Vincent, F. Natali, D. Byrne, A. Vasson, P. Disseix, J. Leymarie, M. Leroux, F. Semond, J. Massies, Phys. Rev. B 68 (2003) 153313], we have highlighted for the first time the exciton–photon strong coupling in a GaN-based microcavity and obtained a Rabi splitting of 31 meV persistent at 77 K. Our aim is now to study the feasibility of GaN-based microcavities for which the strong coupling regime would be maintained at room temperature. A complex heterostructure containing GaN/AlGaN quantum wells (QWs) is investigated by photoreflectivity and reflectivity at 5 K. The QW thickness is 3 nm and the Al composition and thickness of the barriers are respectively 0.11 and 10 nm. From the modeling of the experimental spectra, the values of the oscillator strength, the energy and the broadening parameter of the QW fundamental transition are determined; the broadening is found to be relatively weak (15 meV). Simulations of microcavities containing QWs have then been performed including this set of parameters: a theoretical Rabi splitting of 34 meV is obtained at 5 K. Considering an additional broadening induced by the increase of the temperature (23 meV), the strong coupling regime could be maintained theoretically at room temperature in such a structure. This is due to the low value of the inhomogeneous broadening related to the QW transition which is lower than in bulk GaN. The influence of the QW number and the nature of the Bragg mirror on the Rabi splitting is then discussed in realistic structures.     

Coherent manipulation of spin squeezing in atomic Bose-Einstein condensate via electromagnetically induced transparency

We propose a scheme to coherently control spin squeezing of atomic Bose-Einstein condensate (BEC) via the technique of electromagnetically induced transparency (EIT). We study quantum dynamics of the mean spin vector and spin squeezing. It is shown that the mean spin vector and spin squeezing of the BEC can be controlled and manipulated by adjusting the external coupling fields or/and internal nonlinear interactions of the BEC. It is indicated that the spin squeezing can be generated rapidly in the dynamical process and maintained in a long time interval. It is found that a larger effective Rabi coupling between atoms and lasers can produce a stronger spin squeezing, and the squeezing can maintain a longer time interval.     

Photonic realization of the quantum Rabi model

We realize a photonic analog simulator of the quantum Rabi model, based on light transport in femtosecond-laser-written waveguide superlattices, which provides an experimentally accessible test bed to explore the physics of light-matter interaction in the deep strong coupling regime. Our optical setting enables us to visualize dynamical regimes not yet accessible in cavity or circuit quantum electrodynamics, such as the bouncing of photon number wave packets in parity chains of Hilbert space.     

Hybrid excitons in organic–inorganic semiconducting quantum wells in a microcavity

We investigate theoretically the optical properties of composite organic–inorganic semiconductor quantum wells. These properties are dominated by hybrid Frenkel (or charge-transfer) and Wannier–Mott excitonic states. An important effect is the possibility of using the Stark shift to tune the resonance between Frenkel and Wannier–Mott excitons. This fact is very important from a practical point of view because it may be difficult to grow such a structure exactly at resonance. We also discussed the coupling of Frenkel or charge transfer and Wannier–Mott exciton through a microcavity photon. We evaluate the hybrid exciton-polariton Rabi splitting. In the strong coupling regime the Rabi splitting depends essentially on the oscillator strength of the Frenkel or charge-transfer exciton.