23,371 research outputs found

### Evidence of spin liquid with hard-core bosons in a square lattice

We show that laser assisted hopping of hard core bosons in a square optical
lattice can be described by an antiferromagnetic $J_{1}$-$J_{2}$ XY model with
tunable ratio of $J_{2}/J_{1}$. We numerically investigate the phase diagram of
the $J_{1}$-$J_{2}$ XY model using both the tensor network algorithm for
infinite systems and the exact diagonalization for small clusters and find
strong evidence that in the intermediate region around $% J_{2}/J_{1}\sim 0.5$,
there is a spin liquid phase with vanishing magnetization and valence bond
orders, which interconnects the Neel state on the $J_{2}\ll J_{1}$ side and the
stripe antiferromagnetic phase on the $% J_{2}\gg J_{1}$ side. This finding
opens up the possibility of studying the exotic spin liquid phase in a
realistic experimental system using ultracold atoms in an optical lattice.Comment: 5 pages, 5 figure

### Efficient Quantum Computation with Probabilistic Quantum Gates

With a combination of the quantum repeater and the cluster state approaches, we show that efficient quantum computation can be constructed even if all the entangling quantum gates only succeed with an arbitrarily small probability p. The required computational overhead scales efficiently both with 1/p and n, where n is the number of qubits in the computation. This approach provides an efficient way to combat noise in a class of quantum computation implementation schemes, where the dominant noise leads to probabilistic signaled errors with an error probability 1-p far beyond any threshold requirement

### Nonlocal Dynamics of Passive Tracer Dispersion with Random Stopping

We investigate the nonlocal behavior of passive tracer dispersion with random
stopping at various sites in fluids. This kind of dispersion processes is
modeled by an integral partial differential equation, i.e., an
advection-diffusion equation with a memory term. We have shown the exponential
decay of the passive tracer concentration, under suitable conditions for the
velocity field and the probability distribution of random stopping time.Comment: 7 page

### Topology of Knotted Optical Vortices

Optical vortices as topological objects exist ubiquitously in nature. In this
paper, by making use of the $\phi$-mapping topological current theory, we
investigate the topology in the closed and knotted optical vortices. The
topological inner structure of the optical vortices are obtained, and the
linking of the knotted optical vortices is also given.Comment: 11 pages, no figures, accepted by Commun. Theor. Phys. (Beijing, P.
R. China

### Supersolid and charge density-wave states from anisotropic interaction in an optical lattice

We show anisotropy of the dipole interaction between magnetic atoms or polar
molecules can stabilize new quantum phases in an optical lattice. Using a well
controlled numerical method based on the tensor network algorithm, we calculate
phase diagram of the resultant effective Hamiltonian in a two-dimensional
square lattice - an anisotropic Hubbard model of hard-core bosons with
attractive interaction in one direction and repulsive interaction in the other
direction. Besides the conventional superfluid and the Mott insulator states,
we find the striped and the checkerboard charge density wave states and the
supersolid phase that interconnect the superfluid and the striped solid states.
The transition to the supersolid phase has a mechanism different from the case
of the soft-core Bose Hubbard model.Comment: 5 pages, 5 figures

### Entanglement-assisted transformation is asymptotically equivalent to multiple-copy transformation

We show that two ways of manipulation of quantum entanglement, namely,
entanglement-assisted local transformation [D. Jonathan and M. B. Plenio, Phys.
Rev. Lett. {\bf 83}, 3566 (1999)] and multiple-copy transformation [S.
Bandyopadhyay, V. Roychowdhury, and U. Sen, Phys. Rev. A {\bf 65}, 052315
(2002)], are equivalent in the sense that they can asymptotically simulate each
other's ability to implement a desired transformation from a given source state
to another given target state with the same optimal success probability. As a
consequence, this yields a feasible method to evaluate the optimal conversion
probability of an entanglement-assisted transformation.Comment: 5 pages, revtex4, references updated, no figures. A slightly shorter
version appears in PR

### Evolution of the Chern-Simons Vortices

Based on the gauge potential decomposition theory and the $\phi$-mapping
theory, the topological inner structure of the Chern-Simons-Higgs vortex has
been showed in detail. The evolution of CSH vortices is studied from the
topological properties of the Higgs scalar field. The vortices are found
generating or annihilating at the limit points and encountering, splitting or
merging at the bifurcation points of the scalar field $\phi .$Comment: 10 pages, 10 figure

### Disclination in Lorentz Space-Time

The disclination in Lorentz space-time is studied in detail by means of
topological properties of $\phi$-mapping. It is found the space-time
disclination can be described in term of a Dirac spinor. The size of the
disclination, which is proved to be the difference of two sets of su(2)% -like
monopoles expressed by two mixed spinors, is quantized topologically in terms
of topological invariants$-$winding number. The projection of space-time
disclination density along an antisymmetric tensor field is characterized by
Brouwer degree and Hopf index.Comment: Revtex, 7 page

### Neutrinos, Weak Interactions, and r-process Nucleosynthesis

Two of the key issues in understanding the neutron-to-proton ratio in a
core-collapse supernova are discussed. One of these is the behavior of the
neutrino-nucleon cross sections as supernova energies. The other issue is the
many-body properties of the neutrino gas near the core when both one- and
two-body interaction terms are included.Comment: To be published in the Proceedings of "International Symposium on
Structure of Exotic Nuclei and Nuclear Forces (SENUF 06)", March 2006, Tokyo,
Japa

### Effect of Transition Magnetic Moments on Collective Supernova Neutrino Oscillations

We study the effect of Majorana transition magnetic moments on the flavor
evolution of neutrinos and antineutrinos inside the core of Type-II supernova
explosions. We find non-trivial collective oscillation effects relating
neutrinos and antineutrinos of different flavors, even if one restricts the
discussion to Majorana transition electromagnetic moment values that are not
much larger than those expected from standard model interactions and nonzero
neutrino Majorana masses. This appears to be, to the best of our knowledge, the
only potentially observable phenomenon sensitive to such small values of
Majorana transition magnetic moments. We briefly comment on the effect of Dirac
transition magnetic moments and on the consequences of our results for future
observations of the flux of neutrinos of different flavors from a nearby
supernova explosion.Comment: 11 pages,appendix added, version accepted in JCA

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