6,085 research outputs found
Cross-Kerr-based information transfer processes
The realization of nonclassical states is an important task for many
applications of quantum information processing. Usually, properly tailored
interactions, different from goal to goal, are considered in order to
accomplish specific tasks within the general framework of quantum state
engineering. In this paper we remark on the flexibility of a cross-Kerr
nonlinear coupling in hybrid systems as an important ingredient in the
engineering of nonclassical states. The general scenario we consider is the
implementation of high cross-Kerr nonlinearity in cavity-quantum
electrodynamics. In this context, we discuss the possibility of performing
entanglement transfer and swapping between a qubit and a continuous-variable
state. The recently introduced concept of entanglement reciprocation is also
considered and shown to be possible with our scheme. We reinterpret some of our
results in terms of applications of a generalized Ising interaction to systems
of different nature.Comment: 8 pages, 4 figures, RevTeX
Nonfrustrated magnetoelectric with incommensurate magnetic order in magnetic field
We discuss a model nonfrustrated magnetoelectric in which strong enough
magnetoelectric coupling produces incommensurate magnetic order leading to
ferroelectricity. Properties of the magnetoelectric in magnetic field directed
perpendicular to wave vector describing the spin helix are considered in
detail. Analysis of classical energy shows that in contrast to naive
expectation the onset of ferroelectricity takes place at a field that
is lower than the saturation field . One has at strong
enough magnetoelectric coupling. We show that at H=0 the ferroelectricity
appears at . Qualitative discussion of phase diagram in
plane is presented within mean field approach.Comment: 12 pages, 3 figures, accepted in JET
Magnetic Order and Spin Dynamics in Ferroelectric HoMnO
Hexagonal HoMnO is a frustrated antiferromagnet (T=72 K)
ferroelectric (T=875 K) in which these two order parameters are coupled.
Our neutron measurements of the spin wave dispersion for the S=2 Mn on
the layered triangular lattice are well described by a two-dimensional
nearest-neighbor Heisenberg exchange J=2.44 meV, and an anisotropy that is
0.093 meV above the spin reorientation transition at 40 K, and 0.126 meV below.
For the magnetic structures and phase diagram have been
determined, and reveal additional transitions below 8 K where the
ferroelectrically displaced Ho ions are ordered magnetically.Comment: To be published in Physical Review Letter
Melting of Quasi-Two-Dimensional Charge Stripes in La5/3Sr1/3NiO4
Commensurability effects for nickelates have been studied by the first
neutron experiments on La5/3Sr1/3NiO4. Upon cooling, this system undergoes
three successive phase transitions associated with quasi-two-dimensional (2D)
commensurate charge and spin stripe ordering in the NiO planes. The two
lower temperature phases (denoted as phase II and III) are stripe lattice
states with quasi-long-range in-plane charge correlation. When the lattice of
2D charge stripes melts, it goes through an intermediate glass state (phase I)
before becoming a disordered liquid state. This glass state shows short-range
charge order without spin order, and may be called a "stripe glass" which
resembles the hexatic/nematic state in 2D melting.Comment: 10 pages, RevTex, 4 figures available on request to
[email protected]
Electromagnons in multiferroic YMn2O5 and TbMn2O5
Based on temperature dependent far infrared transmission spectra of YMn2O5
and TbMn2O5 single crystals, we report the observation of electric
dipole-active magnetic excitations, or electromagnons, in these multiferroics.
Electromagnons are found to be directly responsible for the step-like anomaly
of the static dielectric constant at the commensurate--incommensurate magnetic
transition and are the origin of the colossal magneto-dielectric effect
reported in these multiferroics.Comment: 4 pages, 4 figures, submitte
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