8,447 research outputs found
Josephson Oscillation and Transition to Self-Trapping for Bose-Einstein-Condensates in a Triple-Well Trap
We investigate the tunnelling dynamics of Bose-Einstein-Condensates(BECs) in
a symmetric as well as in a tilted triple-well trap within the framework of
mean-field treatment. The eigenenergies as the functions of the zero-point
energy difference between the tilted wells show a striking entangled star
structure when the atomic interaction is large. We then achieve insight into
the oscillation solutions around the corresponding eigenstates and observe
several new types of Josephson oscillations. With increasing the atomic
interaction, the Josephson-type oscillation is blocked and the self-trapping
solution emerges. The condensates are self-trapped either in one well or in two
wells but no scaling-law is observed near transition points. In particular, we
find that the transition from the Josephson-type oscillation to the
self-trapping is accompanied with some irregular regime where tunnelling
dynamics is dominated by chaos. The above analysis is facilitated with the help
of the Poicar\'{e} section method that visualizes the motions of BECs in a
reduced phase plane.Comment: 10 pages, 11 figure
Spinor Decomposition of SU(2) Gauge Potential and The Spinor Structures of Chern-Simons and Chern Density
In this paper, the decomposition of SU(2) gauge potential in terms of Pauli
spinors is studied. Using this decomposition, the spinor strutures of the
Chern-Simons form and the Chern density are obtained. Furthermore, by these
spinor structures, the knot quantum number of non-Abelian gauge theory is
discussed, and the second Chern number is characterized by the Hopf indices and
the Brouwer degrees of -mapping.Comment: 11 page
Optimized Decimation of Tensor Networks with Super-orthogonalization for Two-Dimensional Quantum Lattice Models
A novel algorithm based on the optimized decimation of tensor networks with
super-orthogonalization (ODTNS) that can be applied to simulate efficiently and
accurately not only the thermodynamic but also the ground state properties of
two-dimensional (2D) quantum lattice models is proposed. By transforming the 2D
quantum model into a three-dimensional (3D) closed tensor network (TN)
comprised of the tensor product density operator and a 3D brick-wall TN, the
free energy of the system can be calculated with the imaginary time evolution,
in which the network Tucker decomposition is suggested for the first time to
obtain the optimal lower-dimensional approximation on the bond space by
transforming the TN into a super-orthogonal form. The efficiency and accuracy
of this algorithm are testified, which are fairly comparable with the quantum
Monte Carlo calculations. Besides, the present ODTNS scheme can also be
applicable to the 2D frustrated quantum spin models with nice efficiency
Josephson dynamics of a spin-orbit coupled Bose-Einstein condensate in a double well potential
We investigate the quantum dynamics of an experimentally realized spin-orbit
coupled Bose-Einstein condensate in a double well potential. The spin-orbit
coupling can significantly enhance the atomic inter-well tunneling. We find the
coexistence of internal and external Josephson effects in the system, which are
moreover inherently coupled in a complicated form even in the absence of
interatomic interactions. Moreover, we show that the spin-dependent tunneling
between two wells can induce a net atomic spin current referred as spin
Josephson effects. Such novel spin Josephson effects can be observable for
realistically experimental conditions.Comment: 8 page
Maximal violation of Clauser-Horne-Shimony-Holt inequality for four-level systems
Clauser-Horne-Shimony-Holt inequality for bipartite systems of 4-dimension is
studied in detail by employing the unbiased eight-port beam splitters
measurements. The uniform formulae for the maximum and minimum values of this
inequality for such measurements are obtained. Based on these formulae, we show
that an optimal non-maximally entangled state is about 6% more resistant to
noise than the maximally entangled one. We also give the optimal state and the
optimal angles which are important for experimental realization.Comment: 7 pages, three table
- …