172,643 research outputs found
Pentaquarks
Since LEPS collaboration reported the first evidence of pentaquark
in early 2003, eleven other experimental groups have confirmed this exotic
state while many other groups didn't see any signal. If this state is further
established by future high statistical experiments, its discovery shall be one
of the most important events in hadron physics for the past three decades. This
exotic baryon with such a low mass and so narrow a width imposes a big
challenge to hadron theorists. Up to now, there have appeared more than two
hundred theoretical papers trying to interpret this charming state. I will
review some important theoretical developments on pentaquarks based on my
biased personal views.Comment: Review Commissioned by International Journal of Modern Physics
Thermal Entanglement between Alternate Qubits of a Four-qubit Heisenberg XX Chain in a Magnetic Field
The concurrence of two alternate qubits in a four-qubit Heisenberg XX chain
is investigated when a uniform magnetic field B is included. It is found that
there is no thermal entanglement between alternate qubits if B is close to
zero. Magnetic field can induce entanglement in a certain range both for the
antiferromagnetic and ferromagnetic cases. Near zero temperature, the
entanglement undergoes two sudden changes with increasing value of the magnetic
field B. This is due to the changes in the ground state. This novel property
may be used as quantum entanglement switch. The anisotropy in the system can
also induce the entanglement between two alternate qubits.Comment: 10 pages, 3 figure
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