58,328 research outputs found
Distributed coherent manipulation of qutrits by virtual excitation processes
We propose a scheme for the deterministic coherent manipulation of two atomic
qutrits, trapped in separate cavities coupled through a short optical fibre or
optical resonator. We study such a system in the regime of dispersive
atom-field interactions, where the dynamics of atoms, cavities and fibre
operates through virtual population of both the atomic excited states and
photonic states in the cavities and fibre. We show that the resulting effective
dynamics allows for the creation of robust qutrit entanglement, and thoroughly
investigate the influence of imperfections and dissipation, due to atomic
spontaneous emission and photon leakage, on the entanglement of the two qutrits
state.Comment: 15 pages, 4 figure
Phase transitions in the Shastry-Sutherland lattice
Two recently developed theoretical approaches are applied to the
Shastry-Sutherland lattice, varying the ratio between the couplings on
the square lattice and on the oblique bonds. A self-consistent perturbation,
starting from either Ising or plaquette bond singlets, supports the existence
of an intermediate phase between the dimer phase and the Ising phase. This
existence is confirmed by the results of a renormalized excitonic method. This
method, which satisfactorily reproduces the singlet triplet gap in the dimer
phase, confirms the existence of a gapped phase in the interval
Comment: Submited for publication in Phys. Rev.
Topologically protected elastic waves in phononic metamaterials
Topological states of quantum matter exhibit unique disorder-immune surface
states protected by underlying nontrivial topological invariants of the bulk.
Such immunity from backscattering makes topological surface or edge states
ideal carriers for both classical and quantum information. So far, topological
matters have been explored only in the realms of electronics and photonics,
with limited range of bulk properties and largely immutable materials. These
constraints thus impose severe performance trade-offs in experimentally
realizable topologically ordered states. In contrast, phononic metamaterials
not only provide access to a much wider range of material properties, but also
allow temporal modulation in the non-adiabatic regime. Here, from the
first-principles we demonstrate numerically the first phononic topological
metamaterial in an elastic-wave analogue of the quantum spin Hall effect. A
dual-scale phononic crystal slab is used to support two effective spins of
phonon over a broad bandwidth, and strong spin-orbit coupling is realized by
breaking spatial mirror symmetry. By preserving the spin polarization with an
external load or spatial symmetry, phononic edge states are shown to be robust
against scattering from discrete defects as well as disorders in the continuum.
Our system opens up the possibility of realizing topological materials for
phonons in both static and time-dependent regimes.Comment: 19 pages, 6 figure
Phase Ordering Dynamics of Theory with Hamiltonian Equations of Motion
Phase ordering dynamics of the (2+1)- and (3+1)-dimensional theory
with Hamiltonian equations of motion is investigated numerically. Dynamic
scaling is confirmed. The dynamic exponent is different from that of the
Ising model with dynamics of model A, while the exponent is the same.Comment: to appear in Int. J. Mod. Phys.
Achieving control of in-plane elastic waves
We derive the elastic properties of a cylindrical cloak for in-plane coupled
shear and pressure waves. The cloak is characterized by a rank 4 elasticity
tensor with 16 spatially varying entries which are deduced from a geometric
transform. Remarkably, the Navier equations retain their form under this
transform, which is generally untrue [Milton et al., New J. Phys. 8, 248
(2006)]. We numerically check that clamped and freely vibrating obstacles
located inside the neutral region are cloaked disrespectful of the frequency
and the polarization of an incoming elastic wave.Comment: 9 pages, 4 figure
Dynamics of two atoms coupled to a cavity field
We investigate the interaction of two two-level atoms with a single mode
cavity field. One of the atoms is exactly at resonance with the field, while
the other is well far from resonance and hence is treated in the dispersive
limit. We find that the presence of the non-resonant atom produces a shift in
the Rabi frequency of the resonant atom, as if it was detuned from the field.
We focus on the discussion of the evolution of the state purity of each atom.Comment: LaTex, 2 figure
Trapping and guiding surface plasmons in curved graphene landscapes
We demonstrate that graphene placed on top of structured substrates offers a
novel approach for trapping and guiding surface plasmons. A monolayer graphene
with a spatially varying curvature exhibits an effective trapping potential for
graphene plasmons near curved areas such as bumps, humps and wells. We derive
the governing equation for describing such localized channel plasmons guided by
curved graphene and validate our theory by the first-principle numerical
simulations. The proposed confinement mechanism enables plasmon guiding by the
regions of maximal curvature, and it offers a versatile platform for
manipulating light in planar landscapes. In addition, isolated deformations of
graphene such as bumps are shown to support localized surface modes and
resonances suggesting a new way to engineer plasmonic metasurfaces.Comment: 6 pages, 4 figure
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