Collective Tunnelling of Strongly Interacting Cold Atoms in a Double-Well Potential

It is known that under resonance conditions, a group of strongly interacting bosonic atoms, trapped in a double-well potential, mimics a single particle, performing Rabi oscillations between the wells. By implication, all atoms need to tunnel at roughly the same time, even though the Bose–Hubbard Hamiltonian accounts only for one-atom-at-a-time transfers. The mechanism of this collective behavior is analyzed, the Rabi frequencies in the process are evaluated, and the limitation of this simple picture is discussed. In particular, it is shown that the small rapid oscillations superimposed on the slow Rabi cycle result from splitting the transferred cluster at the sudden onset of tunnelling, and disappear if tunnelling is turned on gradually.     

VIC Effect and Phase-Dependent Optical Properties of Five-Level K-Type Atoms Interacting with Coherent Laser Fields

Due to interaction with the vacuum of the radiation field, a K-type atomic system with near-degenerate excited and ground levels, which is driven by two strong coherent fields and two weak probe fields, has additional coherence terms -- the vacuum-induced coherence （VIC） terms. In this paper, we find that, if the interference is optimized, the two-photon absorption properties of this atom system can be significantly modified and electromagnetically-induced transparency （EIT） is dependent on this interference. Furthermore, we find that in all the cases the coherence can suppress or enhance the partial two-photon transparency, while the complete transparency window is still strictly preserved, which means that it cannot be affected by the VIC. Another important result is the finding of the crucial role played by the relative phase between the probe and coupling fields： the relative height of absorption peaks can be modulated by the relative phase. The physical interpretation of the phenomena has been given.     

VIC Effect and Phase-Dependent Optical Properties of Five-Level K-Type Atoms Interacting with Coherent Laser Fields

Due to interaction with the vacuum of the radiation field, a K-type atomic system with near-degenerate excited and ground levels, which is driven by two strong coherent fields and two weak probe fields, has additional coherence terms — the vacuum-induced coherence (VIC) terms. In this paper, we find that, if the interference is optimized, the two-photon absorption properties of this atom system can be significantly modified and electromagnetically-induced transparency (EIT) is dependent on this interference. Furthermore, we find that in all the cases the coherence can suppress or enhance the partial two-photon transparency, while the complete transparency window is still strictly preserved, which means that it cannot be affected by the VIC. Another important result is the finding of the crucial role played by the relative phase between the probe and coupling fields: the relative height of absorption peaks can be modulated by the relative phase. The physical interpretation of the phenomena has been given.     

光学腔与原子强耦合的实验研究进展

光学腔与原子强耦合系统是量子物理研究的基本系统,不但具有重要的物理意义,而且为量子信息、量子计算和量子精密测量中关键技术的产生和关键器件的研发提供了理想系统。强耦合腔与原子相互作用实验从20世纪90年代开始发展,经过多年的研究,在单原子与光学腔强耦合和原子系综与光学腔的耦合研究方面取得了重大进展。随着多原子阵列量子操控技术的进步,可控的多原子阵列与光学微腔强耦合系统近年来成为腔量子电动力学的重要研究方向。然而,目前实现确定性可控的多原子阵列与腔的强耦合仍面临巨大的技术挑战,可控原子数还停留在两个。简要回顾了近年来光频区强耦合腔量子电动力学系统在上述方面的主要实验进展和相应的实验方案,并展望了未来的发展。     

Joule-Thomson Coefficient for Strongly Interacting Unitary Fermi Gas

The Joule-Thomson effect reflects the interaction among constituent particles of macroscopic system. For classical ideal gas, the corresponding .Joule-Thomson coefficient is vanishing while it is non-zero for ideal quantum gas due to the quantum degeneracy. In recent years, much attention is paid to the unitary Fermi gas with infinite two-body scattering length. According to universal analysis, the thermodynamical law of unitary Fermi gas is similar to that of non-interacting ideal gas, which can be explored by the virial theorem P = 2E/3V. Based on previous works, we further study the unitary Fermi gas properties. The effective chemical potential is introduced to characterize the nonlinear levels crossing effects in a strongly interacting medium. The changing behavior of the rescaled Joule-Thomson coefficient according to temperature manifests a quite different behavior from that for ideal Fermi gas.     

Quantum Correlation of Two Entangled Atoms Interacting with the Binomial Optical Field

Quantum correlations of two atoms in a system of two entangled atoms interacting with the binomial optical field are investigated. In eight different initial states of the two atoms, the influence of the strength of the dipole-dipole interaction, probabilities of a the Bernoulli trial and particle number of the binomial optical field on the temporal evolution of the geometrical quantum discord between two atoms are discussed. The result shows that two atoms always exist the correlation for different parameters. In addition, when and only when the two atoms are initially in the maximally entangled state, the temporal evolution of geometrical quantum discord is not affected by the parameters, and always keep in the degree of geometrical quantum discord that is a fixed value.     

Scale-Invariant Structure of the Seismic Kinetics in Strongly Nonequilibrium Medium

Results of the scaling analysis of the waiting time series for seismic events of the 2019 Ridgecrest earthquake sequence in East California have been presented. It has been shown that the waiting time series before a strong earthquake with a magnitude of M = 7.1 acquires a scale-invariant structure. A reason for the appearance of the statistical self-similarity in the waiting time series is the transition of the medium in the focal region to a strongly nonequilibrium state. The result can be interpreted as the appearance of a temporal dissipative structure in the process of seismic kinetics. It has been proposed to use the scaling analysis of the seismic kinetic data to monitor the current state of the seismogenerating medium.

     

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.     

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...     

与非等同双原子相互作用下光场的相干性质

研究了具有不同偶极矩的两个原子与双模压缩真空场相互作用系统中光场的相干性质.讨论了两个原子与双模压缩真空场的相对耦合常量(R=g1/g2)和光场的初始压缩因子r对二阶相干度、光场的模间相关性、Cauchy-Schwartz不等式的影响.结果表明,光场的初始压缩因子较小时,光子的聚束效应和反聚束效应交替出现,且光场的模间相关程度较强.光场的初始压缩因子较大时,光子呈现聚束效应,且模间相关程度较弱.双原子的相对耦合常量R对二阶相干度、光场的模间相关性、Cauchy-Schwartz不等式的时间演化规律有影响,但不能改变光场模间相关的非经典性质.     

与非等同双原子相互作用下光场的量子特性

研究了具有不同偶极矩的两个原子与双模压缩真空场相互作用系统中光场的量子特性.讨论了两个原子与双模压缩真空场的相对耦合常数(R=g1/g2)和光场的初始压缩因子r对光场的压缩效应和光子的聚束与反聚束效应的影响.数值计算结果表明,光场量子涨落的震荡幅度、最大压缩深度、压缩时间及二阶相干度的震荡振幅与光场的初始压缩因子r的大小有关.两原子与双模光场的相对耦合常数R影响着光场量子涨落和二阶相干度的震荡规律,因而也影响着压缩时间、光场处于非经典态的时间及光子的反聚束程度,但对光场的压缩深度无明显影响.     

光场-原子BEC相互作用系统的量子相关性质

运用全量子理论,在Bogoliubov近似下研究了光场与二能级原子玻色-爱因斯坦凝聚体(BEC)相互作用系统的量子相关性质,结果表明:光场和原子玻色-爱因斯坦凝聚体在相互作用过程中,其量子相关性质保持不变.     

Quantum Entanglement and Correlation of Two Qubit Atoms Interacting with the Coherent State Optical Field

International Journal of Theoretical Physics - Using the three criterions of the concurrence, the negative eigenvalue and the geometric quantum discord, we investigate the quantum entanglement and...     

Quantum Statistical Properties of Binomial Field Interacting with Two Entangled Atoms

Quantum statistical properties of the binomial field interacting with the two entangled atoms are investigated for the different initial conditions. It is found that the sub-Poissonian distribution and the antibunching effect can be presented for the certain ranges of the involved parameters.     

克尔介质中双模纠缠相干光与贝尔态原子相互作用系统的光子统计特性

运用全量子理论并结合数值计算方法,研究了克尔介质腔中处于贝尔态的两个全同二能级纠缠原子与双模纠缠相干光场相互作用系统的光子统计特性。讨论了双原子体系的初态、初始光场的平均光子数、双模纠缠相干光场的纠缠程度以及克尔介质与双模光场的耦合强度对光子统计特性的影响。结果表明:忽略克尔介质的作用时,只有当双原子体系的初态为0β1〉或1β1〉时,在一定的条件下才可出现光子的反聚束效应,而当双原子体系的初态为β00〉、1β0〉时,光场在其演化过程中不出现光子的反聚束效应。而当考虑克尔介质的作用时,四种初态下光场演化过程中均有可能出现光子的反聚束效应。光子的反聚束效应出现的次数、时间和深度极其敏感地依赖于初始光场的平均光子数和克尔介质与双模光场的耦合强度,同时也受到双模纠缠光场的纠缠程度的影响。     

原子与热库相互作用系统中的三体纠缠特性

利用Ket-Bra纠缠态方法,求解了原子与热库相互作用系统中的密度矩阵主方程,得到了密度矩阵的演化表达式.考虑三个二能级原子独立与热库相互作用的情况,利用负本征值度量三体纠缠,研究了系统中原子间的三体纠缠特性.采用数值计算方法,讨论了热库平均光子数和原子自发辐射率对原子间三体纠缠特性的影响.研究结果表明:随原子自发辐射率和热库平均光子数的增大,原子间的三体纠缠衰减加快.     

Quantization of Strongly Interacting Fields

While perturbative techniques work extremelywell for weakly interacting field theories (e.g., QED),they are not useful when studying strongly interactingfield theories (e.g., QCD at low energies). In this paper we review Heisenberg's idea aboutquantizing strongly interacting nonlinear fields, andsuggest an approximate method of solving the infiniteset of Tamm-Dankoff equations. We then apply this procedure to an infinite-energy, classicalflux-tube-like solution of SU(2) Yang-Mills theory andshow that this quantization procedure ameliorates someof the bad behavior of the classical solution. We also discuss the possible application of thisquantization procedure to a recently proposed stronglyinteracting phonon model of high-T_csuperconductors.     

原子与弱相干腔场相互作用系统中的量子特性

考虑腔场处于弱相干态的情况,研究了两个全同的二能级原子与耦合腔相互作用系统中原子的偶极压缩和原子间的纠缠特性。研究结果表明,随耦合腔耦合系数增大,原子的偶极压缩减弱。另一方面,随耦合腔耦合系数增大,原子间的纠缠也减弱,这一结果与耦合腔处于真空态的情况相反。     

Kerr介质中双原子-压缩真空场系统的腔场谱

研究了含Kerr介质腔中耦合双原子间与双模均处于压缩真空态的光场拉曼相互作用过程的腔场谱.通过求解本征方程导出了双模光场处于任意强度时腔场谱的计算公式,给出了数值计算结果.发现在两模初始场均为弱场时,Kerr介质和原子间的耦合作用对谱结构的影响较小;当双模初始场均为强场时,两模主峰的右侧出现了半梳状边峰,随Kerr效应的增强,峰间距逐渐加宽,并向高频方向扩展,在Kerr效应较强时,两模边峰的峰高出现高低相间的现象.     

Kerr介质中耦合全同Λ型三能级原子与真空场相互作用过程中场熵的演化特性

利用量子理论,研究了真空场与耦合全同Λ型三能级原子相互作用过程中场熵的演化特性.讨论了系统初始状态、失谐量、原子间偶极相互作用和Kerr系数对场熵演化特性的影响.数值计算结果表明:场熵呈现出周期性振荡,其振荡频率和幅度强烈地依赖于系统的初始状态|失谐量、原子间耦合强度、Kerr系数的增大,都会使场熵振荡的幅度减小.