34,284 research outputs found
Geometric phases in a scattering process
The study of geometric phase in quantum mechanics has so far be confined to
discrete (or continuous) spectra and trace preserving evolutions. Consider only
the transmission channel, a scattering process with internal degrees of freedom
is neither a discrete spectrum problem nor a trace preserving process. We
explore the geometric phase in a scattering process taking only the
transmission process into account. We find that the geometric phase can be
calculated by the some method as in an unitary evolution. The interference
visibility depends on the transmission amplitude. The dependence of the
geometric phase on the barrier strength and the spin-spin coupling constant is
also presented and discussed.Comment: 4 pages, 5 figure
Effect of spin relaxations on the spin mixing conductances for a bilayer structure
The spin current can result in a spin-transfer torque in the
normal-metal(NM)|ferromagnetic-insulator(FMI) or
normal-metal(NM)|ferromagnetic-metal(FMM) bilayer. In the earlier study on this
issue, the spin relaxations were ignored or introduced phenomenologically. In
this paper, considering the FMM or FMI with spin relaxations described by a
non-Hermitian Hamiltonian, we derive an effective spin-transfer torque and an
effective spin mixing conductance in the non-Hermitian bilayer. The dependence
of the effective spin mixing conductance on the system parameters (such as
insulating gap, \textit{s-d} coupling, and layer thickness) as well as the
relations between the real part and the imaginary part of the effective spin
mixing conductance are given and discussed. We find that the effective spin
mixing conductance can be enhanced in the non-Hermitian system. This provides
us with the possibility to enhance the spin mixing conductance
Spontaneous spin textures in dipolar spinor condensates
We have mapped out a detailed phase diagram that shows the ground state
structure of a spin-1 condensate with magnetic dipole-dipole interactions. We
show that the interplay between the dipolar and the spin-exchange interactions
induces a rich variety of quantum phases that exhibit spontaneous magnetic
ordering in the form of intricate spin textures.Comment: 4.1 pages, 4 figure
A conditional quantum phase gate between two 3-state atoms
We propose a scheme for conditional quantum logic between two 3-state atoms
that share a quantum data-bus such as a single mode optical field in cavity QED
systems, or a collective vibrational state of trapped ions. Making use of
quantum interference, our scheme achieves successful conditional phase
evolution without any real transitions of atomic internal states or populating
the quantum data-bus. In addition, it only requires common addressing of the
two atoms by external laser fields.Comment: 8 fig
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