15,079 research outputs found
Disclination in Lorentz Space-Time
The disclination in Lorentz space-time is studied in detail by means of
topological properties of -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 invariantswinding 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
Entanglement dynamics of a two-qubit system coupled individually to Ohmic baths
Developed originally for the Holstein polaron, the Davydov D1 ansatz is an
efficient, yet extremely accurate trial state for time-dependent variation of
the spin-boson model [J. Chem. Phys. 138, 084111 (2013)]. In this work, the
Dirac-Frenkel time-dependent variational procedure utilizing the Davydov D1
ansatz is implemented to study entanglement dynamics of two qubits under the
influence of two independent baths. The Ohmic spectral density is used without
the Born-Markov approximation or the rotating-wave approximation. In the strong
coupling regime finite-time disentanglement is always found to exist, while at
the intermediate coupling regime, the entanglement dynamics calculated by
Davydov D1 ansatz displays oscillatory behavior in addition to entanglement
disappearance and revival.Comment: 8 pages, 3 figure
A dynamical approximation for stochastic partial differential equations
Random invariant manifolds often provide geometric structures for
understanding stochastic dynamics. In this paper, a dynamical approximation
estimate is derived for a class of stochastic partial differential equations,
by showing that the random invariant manifold is almost surely asymptotically
complete. The asymptotic dynamical behavior is thus described by a stochastic
ordinary differential system on the random invariant manifold, under suitable
conditions. As an application, stationary states (invariant measures) is
considered for one example of stochastic partial differential equations.Comment: 28 pages, no figure
Efficient engineering of multi-atom entanglement through single-photon detections
We propose an efficient scheme to engineer multi-atom entanglement by
detecting cavity decay through single-photon detectors. In the special case of
two atoms, this scheme is much more efficient than previous probabilistic
schemes, and insensitive to randomness in the atom's position. More generally,
the scheme can be used to prepare arbitrary superpositions of multi-atom Dicke
states without the requirements of high-efficiency detection and separate
addressing of different atoms.Comment: 5 pages, 2 figure
Stabilization of the p-wave superfluid state in an optical lattice
It is hard to stabilize the p-wave superfluid state of cold atomic gas in
free space due to inelastic collisional losses. We consider the p-wave Feshbach
resonance in an optical lattice, and show that it is possible to have a stable
p-wave superfluid state where the multi-atom collisional loss is suppressed
through the quantum Zeno effect. We derive the effective Hamiltonian for this
system, and calculate its phase diagram in a one-dimensional optical lattice.
The results show rich phase transitions between the p-wave superfluid state and
different types of insulator states induced either by interaction or by
dissipation.Comment: 5 pages, 5 figure
Quantum superposition of multiple clones and the novel cloning machine
we envisage a novel quantum cloning machine, which takes an input state and
produces an output state whose success branch can exist in a linear
superposition of multiple copies of the input state and the failure branch
exist in a superposition of composite state independent of the input state. We
prove that unknown non-orthogonal states chosen from a set can evolve
into a linear superposition of multiple clones by a unitary process if and only
if the states are linearly independent. We derive a bound on the success
probability of the novel cloning machine. We argue that the deterministic and
probabilistic clonings are special cases of our novel cloning machine.Comment: Two column, 5 pages, Latex, some additions, minor changes. Phys. Rev.
Lett. (To appear, 1999
Inseparability criterion for continuous variable systems
An inseparability criterion based on the total variance of a pair of
Einstein-Podolsky-Rosen type operators is proposed for continuous variable
systems. The criterion provides a sufficient condition for entanglement of any
two-party continuous variable states. Furthermore, for all the Gaussian states,
this criterion turns out to be a necessary and sufficient condition for
inseparability.Comment: minor changes in the introduction and ref
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