Scattering quantum bright solitons off barriers has been predicted to lead to nonlocal quantum superpositions, in particular the NOON-state. The focus of this paper lies on signatures of both high- and low-fidelity quantum superposition states. We numerically demonstrate that a one-dimensional geometry with the barrier potential situated in the middle of an additional - experimentally typical - harmonic confinement gives rise to particularly well-observable signatures. In the elastic scattering regime we investigate signatures of NOON-states on the $N$-particle level within an effective potential approach. We show that removing the barrier potential and subsequently recombining both parts of the quantum superposition leads to a high-contrast interference pattern in the center-of-mass coordinate for narrow and broad potential barriers. We demonstrate that the presented signatures can be used to clearly distinguish quantum superpositions states from statistical mixtures and are sufficiently robust against experimentally relevant excitations of the center-of-mass wave function to higher lying oscillator states. For two-particle solitons we extend these considerations to low-fidelity superposition states: even for strong deviations from the two-particle NOON-state we find interference patterns with high contrast.
Due to their coherence properties, dilute atomic gas Bose-Einstein condensates seem a versatile platform for controlled creation of mesoscopically entangled states with a large number of particles and also allow controlled studies of their decoherence. However, the creation of such a state intrinsically involves many-body quantum dynamics that cannot be captured by mean-field theory, and thus invalidates the most widespread methods for the description of condensates. We follow up on a proposal, in which a condensate cloud as a whole is brought into a superposition of two different spatial loca…
Synthetic spin-tensor-momentum coupling has recently been proposed to realize in atomic Bose-Einstein condensates. Here we study bright solitons in Bose-Einstein condensates with spin-tensor-momentum coupling and spin-orbit coupling. The properties and dynamics of spin-tensor-momentum-coupled and spin-orbit-coupled bright solitons are identified to be different. We contribute the difference to the different symmetries.
Motivated by recent experiments, we model the dynamics of bright solitons formed by cold gases in quasi-1D traps. A dynamical variational ansatz captures the far-from equilibrium excitations of these solitons. Due to a separation of scales, the radial and axial modes decouple, allowing for closed-form approximations for the dynamics. We explore how soliton dynamics influence atom loss, and find that the time-averaged loss is largely insensitive to the degree of excitation. The variational approach enables us to perform high precision calculations of the critical atom number (ie. the maximum nu…
We investigate the dynamics of a dark-bright soliton in a harmonic potential using a mean-field approach via coupled nonlinear Schrödinger equations appropriate to multicomponent Bose-Einstein condensates. We use a modified perturbed dynamical variational Lagrangian approximation, where the perturbation is due to the trap, taken as a Thomas-Fermi profile. The wavefunction ansatz is taken as the correct hyperbolic tangent and secant solutions in the scalar case for the dark and bright components of the soliton, respectively. We also solve the problem numerically with psuedo-spectral Runge-Kutta…
Bright dipolar Bose-Einstein condensate soliton mobile in a direction perpendicular to polarization
我们证明了稳定的，强大的，明亮的偶极玻色-爱因斯坦凝聚体（BEC）孤子，运动方向垂直的偏振方向，形成由于排斥接触相互作用的偶极相互作用。在中等速度下，两个这样的孤子碰撞的头被发现是几乎没有变形的准弹性。在小扰动下，孤子表现出持续的呼吸振荡。研究结果表明，通过数值模拟使用三维平均场Gross-Pitaevskii方程和减少二维模型在三个和两个空间维度采用现实的相互作用参数的偶极$^{164}$ Dy BEC。
We experimentally study the excitation modes of bright matter-wave solitons in a quasi-one-dimensional geometry. The solitons are created by quenching the interactions of a Bose-Einstein condensate of cesium atoms from repulsive to attractive in combination with a rapid reduction of the longitudinal confinement. A deliberate mismatch of quench parameters allows for the excitation of breathing modes of the emerging soliton and for the determination of its breathing frequency as a function of atom number and confinement. In addition, we observe signatures of higher-order solitons and the splitti…
We study the dynamics of a dark-bright soliton interacting with a fixed impurity using a mean-field approach. The system is described by a vector nonlinear Schrodinger equation (NLSE) appropriate to multicomponent Bose-Einstein condensates. We use the variational approximation, based on hyperbolic functions, where we have the center of mass of the two components to describe the propagation of the dark and bright components independently. Therefore, it allows the dark-bright soliton to oscillate. The fixed local impurity is modeled by a delta function. Also, we use perturbation methods to deriv…
We study the formation of stable bright solitons in quasi-one-dimensional (quasi-1D) spin-orbit- (SO-) and Rabi-coupled two pseudospinor dipolar Bose-Einstein condensates (BECs) of 164 Dy atoms in the presence of repulsive contact interactions. As a result of the combined attraction-repulsion effect of both interactions and the addition of SO and Rabi couplings, two kinds of ground states in the form of self-trapped bright solitons can be formed, a plane-wave soliton (PWS) and a stripe soliton (SS). These quasi-1D solitons cannot exist in a condensate with purely repulsive contact interactions…
我们证明了由于偶极排斥接触相互作用而在中心平面上形成的强、稳定、可移动的准一维暗中亮偶极玻色-爱因斯坦凝聚体（BEC）孤子.在中等速度下，两个这样的孤子碰撞的头被发现是几乎没有变形的准弹性。本文还讨论了在实验室中利用相位印记产生偶极明中暗孤子的方案。在偶极二元BEC中可以形成丰富多样的暗中亮孤子，可以是一个暗中亮孤子与一个亮孤子耦合，也可以是两个暗中亮孤子耦合。结果表明，使用数值模拟在三个空间维度采用现实的相互作用参数的偶极164 Dy BEC和二进制164 Dy-162 Dy BEC。
We demonstrate stable and metastable vortex-bright solitons in a three-dimensional spin-orbit-coupled three-component hyperfine spin-1 Bose-Einstein condensate (BEC) using numerical solution and variational approximation of a mean-field model. The spin-orbit coupling provides attraction to form vortex-bright solitons in both attractive and repulsive spinor BECs. The ground state of these vortex-bright solitons is axially symmetric for weak polar interaction. For a sufficiently strong ferromagnetic interaction, we observe the emergence of a fully asymmetric vortex-bright soliton as the ground s…
Two-dimensional bright and dark-in-bright dipolar Bose-Einstein condensate solitons on a one-dimensional optical lattice
研究了一维光格势场中各向异性、稳定、亮偶极和亮中暗偶极准二维玻色-爱因斯坦凝聚体（BEC）孤子的静态和动力学性质.这些孤子在垂直于一维OL陷阱的平面内运动，可以同时具有排斥和吸引的接触相互作用。明中暗孤子是亮孤子的激发态。孤子，当受到一个小的扰动，表现出持续的呼吸振荡。明中暗孤子可以通过对明孤子进行相位压印而产生。在介质速度下，两个孤子之间的碰撞是准弹性的，数值模拟了偶极$^{164}$ Dy BEC的三维平均场Gross-Pitaevskii方程，利用实际的相互作用参数证明了结果.
We show how access to sufficiently flexible trapping potentials could be exploited in the generation of three-dimensional atomic bright matter-wave solitons. Our proposal provides a route towards producing bright solitonic states with good fidelity, in contrast to, for example, a non-adiabatic sweeping of an applied magnetic field through a Feshbach resonance.
A vortex-bright soliton can precess around a fix point. Here, we find numerically that the fixed point and the associated precessional orbits can be shifted by applying a constant driving force on the bright component, the displacement is proportional to the force with a minus sign. This robust dynamics is then discussed theoretically by treating the vortex-bright soliton as an effective point particle, explaining the observed dynamics and predicting new ones that are subsequently confirmed. By appropriately tuning the force, the vortex-bright soliton can be guided following an arbitrary traje…
Stable and mobile two-dimensional dipolar ring-dark-in-bright Bose-Einstein condensate soliton
我们证明了一个强大的，稳定的，移动的二维（2D）偶极环暗中亮（RDB）玻色-爱因斯坦凝聚体（BEC）孤子的排斥接触相互作用，受到谐波陷阱沿$y$方向垂直于偏振方向$z$。这样的RDB孤子有一个环形缺口（密度为零）印在一个2D亮孤子自由移动在$x-z$平面。在中等速度下，两个这样的孤子的迎头碰撞被发现是准弹性的，几乎没有变形。论证了利用相位印记产生RDB孤子的可能性。结果表明，使用数值模拟采用现实的相互作用参数在偶极$^{164}$ Dy BEC。
There has been considerable recent interest in matterwave interferometry with bright solitons in quantum gases with attractive interactions, for applications such as rotation sensing. We model the quantum dynamics of these systems and find that the attractive interactions required for the presence of bright solitons causes quantum phase-diffusion, which severely impairs the sensitivity. We propose a scheme that partially restores the sensitivity, but find that in the case of rotation sensing, it is still better to work in a regime with minimal interactions if possible.
A study of bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is investigated. Formation of soliton trains in the quasi one-dimensional confinement is shown. Additionally, fragmentation of a BEC has been observed outside confinement, in free space. In the end a double BEC production setup for studying soliton collisions is described.
We demonstrate fast control of the interatomic interactions in a Bose-Einstein condensate by coherently coupling two atomic states with intra- and inter-state scattering lengths of opposite signs. We measure the elastic and inelastic scattering properties of the system and find good agreement with a theoretical model describing the interactions between dressed states. In the attractive regime, we observe the formation of bright solitons formed by dressed-state atoms. Finally, we study the response of the system to an interaction quench from repulsive to attractive values, and observe how the r…
Adopting a mean-field Gross-Pitaevskii description for a spinor polariton Bose-Einstein condensates under non-resonant pumping, we investigate the static and dynamical properties of dark-bright solitons. We derive analytically the equation of motion for the center of mass of the dark-bright soliton center, using the Hamiltonian approach. The resulting equation captures how the combination of the open-dissipative character and the spin degrees of freedom of a polariton Bose-Einstein condensate affects the properties of a dark-bright soliton, i.e. the dark-bright soliton relaxes by blending with…
