Biomedical subjects

Wenhua Hai

Publications and source records attributed to Wenhua Hai.

6 recordsLinked to original sources

PubMed2005

Controlling chaos in a weakly coupled array of Bose-Einstein condensates.

The spatial structure of a Bose-Einstein condensate loaded into an optical lattice potential is investigated and the spatially chaotic distributions of the condensates are revealed under the tight-binding approximation. Adding a laser pulse on a proper site of the lattice and treating it as a control signal, control of the chaos in the system is carried out by using the Ott-Grebogi-Yorker scheme. For an appropriate laser pulse, we can suppress the chaos and push the system onto a stable manifold of a target orbit. After the control, a regular distribution, which may be expected in experiments or practical applications, of the condensates in the coordinate space is obtained.

Journal Article↗

PubMed2005

Dynamic chaos and stability of a weakly open Bose-Einstein condensate in a double-well trap.

We investigate the dynamics of a weakly open Bose-Einstein condensate with attractive interaction in a magneto-optical double-well trap. A set of time-dependent ordinary differential equations describing the complex dynamics are derived by using a two-mode approximation. The stability of the stationary solution is analyzed and some stability regions on the parameter space are displayed. In the symmetric well case, the numerical calculations reveal that by adjusting the feeding from the nonequilibrium thermal cloud or the two-body dissipation rate, the system could transit among the periodic motions, chaotic self-trapping states of the Lorenz model, and the steady states with the zero relative atomic population or with the macroscopic quantum self-trapping (MQST). In the asymmetric well case, we find the periodic orbit being a stable two-sided limited cycle with MQST. The results are in good agreement with that of the direct numerical simulations to the Gross-Pitaevskii equation.

Algorithms↗

PubMed2004

Transient and stationary chaos of a Bose-Einstein condensate loaded into a moving optical lattice potential.

Chaotic space-time evolution is investigated for the particle number density of a Bose-Einstein condensate with attractive interatomic interaction loaded into a traveling optical lattice. Melnikov chaos is studied and the weakly chaotic regime is presented analytically. Transitions from transient to stationary chaos in the space-time evolution are illustrated numerically. The results show that, on increasing the strength of the optical potential, the transient chaos falls onto several different attractors. Meanwhile, these attractors undergo a series of period-doubling bifurcations when the optical potential intensity is increased continuously, and eventually stationary chaos arises for a critical depth of the optical lattice. The obstructions to chaos caused by the damping and the motion of lattice are also demonstrated.

Journal Article↗

PubMed2004

Spatial chaos of trapped Bose-Einstein condensate in one-dimensional weak optical lattice potential.

The spatially chaotic attractor in an elongated cloud of Bose-Einstein condensed atoms perturbed by a weak optical lattice potential is studied. The analytical insolvability and numerical incomputability of the atomic number density are revealed by a perturbed solution that illustrates the unpredictability of the deterministic chaos. Although this could lead the nonphysical explosion and unboundedness to the numerical solution, the theoretical analysis offers a criterion to avoid them. Moreover, the velocity field is investigated that exhibits the superfluid property of the chaotic system.

Journal Article↗

PubMed2003

Chaotic atomic tunneling between two periodically driven Bose-Einstein condensates.

The chaotic coherent atomic tunneling between two periodically driven and weakly coupled Bose-Einstein condensates has been investigated. The perturbed correction to the homoclinic orbit is constructed and its boundedness conditions are established that contain the Melnikov criterion for the onset of chaos. We analytically reveal that the chaotic coherent atomic tunneling is deterministic but not predictable. Our numerical calculation shows good agreement with the analytical result and exhibits nonphysically numerical instability. By adjusting the initial conditions, we propose a method to control the unboundedness, which leads the quantum coherent atomic tunneling to predictable periodical oscillation.

Journal Article↗

PubMed2002

Chaotic probability density in two periodically driven and weakly coupled Bose-Einstein condensates.

Using the idea of the macroscopic quantum wave function and the definition of the classical chaos, we analytically reveal that the probability density of two periodically driven and weakly coupled Bose-Einstein condensates is deterministic but not predictable. Numerical calculation for the time evolutions of the chaotic probability density demonstrates the analytical result and exhibits the nonphysical implosions and ultimate unboundedness. A method for controlling the implosions and unboundedness is proposed through adjustment of the initial conditions that leads the probability density to periodically oscillate.

Journal Article↗