Chaotic Dynamics of a Josephson Junction with Nonlinear Damping

We study the chaotic dynamics of a Josephson junction with nonlinear damping. It is found that with the increasing dc bias the system undergoes a process from a biperiodical state to a chaotic one via a period-doubling route. Interestingly, when the value of the dc bias increases further, the number of the chaotic attractors also increases accordingly. These chaotic attractors appear one after another in different intervals and regions with time. Through a feedback controlling strategy the chaos can be effectively suppressed. We also find that the current between the two separated superconductors of the junction can increase or decrease monotonously with time in some parameter spaces.     

Chaotic Dynamics of a Periodically Modulated Josephson Junction

We study the chaotic dynamics of a periodically modulated Josephson junction with damping. The general solution of the first-order perturbed equation is constructed by using the direct perturbation technique. It is theoretically found that the boundedness conditions of the general solution contain the Melnikov chaotic criterion. When the perturbation conditions cannot be satisfied, numerical simulations demonstrate that the system can step into chaos through a period doubling route with the increase of the amplitude of the modulating term. Regulating specific parameters can effectively suppress the chaos.     

Regular and Chaotic Spatial Distribution of Bose-Einstein Condensed Atoms in a Ratchet Potential

We study the regular and chaotic spatial distribution of Bose-Einstein condensed atoms with a space-dependent nonlinear interaction in a ratchet potential. There exists in the system a space-dependent atomic current that can be tuned via Feshbach resonance technique. In the presence of the space-dependent atomic current and a weak ratchet potential, the Smale-horseshoe chaos is studied and the Melnikov chaotic criterion is obtained. Numerical simulations show that the ratio between the intensities of optical potentials forming the ratchet potential, the wave vector of the laser producing the ratchet potential or the wave vector of the modulating laser can be chosen as the controlling parameters to result in or avoid chaotic spatial distributional states.     

一个描述Josephson振动阻尼效应的场方程

在GPE方程的基础上添加了一个耗散项-12γcψ,用来分析双势阱模型的Josephson振荡中的阻尼现象,并得出:凝聚态粒子总数及 Josephson振动的振幅随时间呈指数衰减.     

Josephson Dynamics of a Bose-Einstein Condensate Trapped in a Double-Well Potential

The Josephson equations for a Bose Einstein Condensate gas trapped in a double-well potential are derived with the two-mode approximation by the Gross Pitaevskii equation. The dynamical characteristics of the equations are obtained by the numerical phase diagrams. The nonlinear self-trapping effect appeared in the phase diagrams are emphatically discussed, and the condition EcN 〉 4E3 is presented.     

Cavity-Induced Self-Trapping of a Bose Josephson Junction

We investigate the self-trapping of a Bose Josephson junction, which is dispersively coupled to a driven optical cavity. The cavity-induced nonlinearity is presented analytically, and its effect results in the appearance of the self-trapping for the Bose-Einstein condensates in the Josephson oscillation regime. In addition, there exists competition between the nonlinearitiesinduced by the interatomic interaction and by the driven cavity for the emergences of self-trapping. Our results show that the driven cavity can be utilized as a possible tool to produce the self-trapping for the condensates with weak interatomic interaction.     

Modified Josephson Equation for Mesoscopic Parallel LC Circuit Including a Josephson Junction

By introducing the entangled state representation, parallel LC circuit including a 3osephson junction equation associated with the modification of the motion equation. the Cooper-pair number-phase quantization of the mesoscopic is realized. In the Heisenberg picture, the modified Josephson Faraday equation about the inductance is deduced from the     

Superposition of Coherent States in a Mesoscopic Josephson Junction with Dissipation

A mesoscopic Josephson junction with dissipation is considered. Usually the dissipation in the system is described as a consequence of its coupling to a reservoir. By solving the master equation we show that the state of the junction can evolve in a quantum superposition of two coherent states even when the dissipation is present.``     

Superposition of Coherent States in a Mesoscopic Josephson Junction with Dissipation

A mesoscopic Josephson junction with dissipation is considered. Usually the dissipation in the system is described as a consequence of its coupling to a reservoir. By solving the master equation we show that the state of the junction can evolve in a quantum superposition of two coherent states even when the dissipation is present.     

Determination of Relaxation Time of a Josephson Tunnel Junction

We propose a non-stationary method to measure the energy relaxation time of Josephson tunnel junctions from microwave enhanced escape phenomena. Compared with the previous methods, our method possesses simple and accurate features. Moreover, having determined the energy relaxation time, we can further obtain the coupling strength between the microwave source and the junction by changing the microwave power.     

Chaotic dynamics of a parametrically modulated Josephson junction with quadratic damping

We study the chaotic dynamics of a parametrically modulated Josephson junction with quadratic damping. The Melnikov chaotic criteria are presented. When the perturbation conditions cannot be satisfied, numerical simulations demonstrate that the system can step into chaos via a quasi-periodic route with the increasing of the dc component of the modulation. However, it is numerically demonstrated that adding a feedback to the system can effectively suppress the chaos.     

Characteristics of the Surface-Intrinsic Josephson Junction

During the fabrication of intrinsic Josephson junctions (IJJs) with Bi₂Sr₂CaCu₂O_8+δ (BSCCO) single crystals, the superconductivity of the surface Cu-O layer is degraded because of a deposited metal film on top of the stack. Thus, the characteristics of the surface junction consisting of the surface Cu-O double layers remarkably differ from those of the junctions deep in the stack, which will be referred to as ordinary IJJs. The electrical transport characteristics of the surface junction, such as I-V, I _c′-T, and R-T, show that the critical temperature T _c′ of the surface junction is always lower than that of ordinary IJJs, and that the change of its critical current I _c′ with temperature is different from that of ordinary IIJs. Furthermore, by shunting the surface junction resistively, we are able to observe the AC Josephson effect at 3-mm waveband. Translated from Chinese Journal of Low Temperature Physics, 2005, 27(2) (in Chinese)     

Continuous-Variable Entanglement in a Coupled Field-Mesoscopic Josephson Junction System

Continuous-variable entanglement in the interacting system of a mesoscopic Josephson junction with a squeezed field is investigated. It is shown that when the cavity field is initially prepared in a squeezed vacuum state and the junction in its lowest energy state, the coupling system can evolve into a two-mode Caussian state. The timedependent characteristic function in the Wigner representation for the system is analytically obtained, and the squeezing degree of the initial cavity field turns out to have not only an apparent enhancing but also a weakening effect on the entanglement of the coupling system under suitable parameter conditions.     

Quantum Computation with Two-Level Systems in Current-Biased Josephson Junction

We present a feasible scheme that realizes quantum computation using the two-level systems （TLSs） in Current-biased Josephson junction （CBJJ） under the present experimental technology. Effective manipulation of the TLSs by CBJJ serving as register qubit can be obtained, such as initialization, single-qubit rotations, two-qubit gates, entanglement generation, and read out, etc. In addition, we also discuss the experimental feasibility and efficiency of the scheme.     

Oscillatory Regimes in a 1D Josephson Junction Array with a Nonlocal Delayed Coupling

Technical Physics - We have numerically investigated a series array of electromagnetically coupled Josephson junctions considering the coupling delay. In the general case of a nonzero delay, we...     

SSeS超导结的约瑟夫逊效应

以推广的 Jacobson方法 ,从 Ginzburg- L andau方程出发 ,推导出了 SSe S超导结的直流约瑟夫逊效应 ,从而进一步求得了 SSe S超导结的临界电流与温度之间的关系 ,以及对结区厚度的依赖性     

约瑟夫森结与阵列的非线性混沌行为及研究进展

约瑟夫森结是一种利用超导材料制备的新型量子电子器件,它的一个显著特性是具有高度的非线性,因而会出现明显的混沌行为。约瑟夫森结与阵列的混沌行为具有重要的研究和应用价值,受到了广泛的关注。文中对约瑟夫森结与阵列的非线性混沌行为及研究进展做一些介绍。     

Quantum Superposition of Two Coherent States in a Mesoscopic Josephson Junction

We study a mesoscopic Josephson junction in a circular superconducting ring which encloses a magneto static flux. It is shown that with the junction being initially prepared in vacuum state, the state of the junction can evolve into a quantum superposition of two coherent states.