703 research outputs found
Quantum metrology enhanced by the spin interaction in a generalized Tavis-Cummings model
Quantum metrology is recognized for its capability to offer high-precision
estimation by utilizing quantum resources, such as quantum entanglement. Here,
we propose a generalized Tavis-Cummings model by introducing the spin
interaction to explore the impact of the many-body effect on estimation
precision, quantified by the quantum Fisher information (QFI). By deriving the
effective description of our model, we establish a closed relationship between
the QFI and the spin fluctuation induced by the spin interaction. Based on
this exact relation, we emphasize the indispensable role of the spin anisotropy
in achieving the Heisenberg-scaling precision for estimating a weak magnetic
field. Furthermore, we observe that the estimation precision can be enhanced by
increasing the strength of the spin anisotropy. We also reveal a clear scaling
transition of the QFI in the Tavis-Cummings model with the reduced Ising
interaction. Our results contribute to the enrichment of metrology theory by
considering many-body effects, and they also present an alternative approach to
improving the estimation precision by harnessing the power provided by
many-body quantum phases
The subordinated processes controlled by a family of subordinators and corresponding Fokker-Planck type equations
In this work, we consider subordinated processes controlled by a family of
subordinators which consist of a power function of time variable and a negative
power function of stable random variable. The effect of parameters in
the subordinators on the subordinated process is discussed. By suitable
variable substitutions and Laplace transform technique, the corresponding
fractional Fokker-Planck-type equations are derived. We also compute their mean
square displacements in a free force field. By choosing suitable ranges of
parameters, the resulting subordinated processes may be subdiffusive, normal
diffusive or superdiffusive.Comment: 11 pages, accepted by J. Stat. Mech.: Theor. Ex
Threshold resummation for the production of a color sextet (antitriplet) scalar at the LHC
We investigate threshold resummation effects in the production of a color
sextet (antitriplet) scalar at next-to-next-to-leading logarithmic (NNLL) order
at the LHC in the frame of soft-collinear effective theory. We show the total
cross section and the rapidity distribution with NLO+NNLL accuracy, and we
compare them with the NLO results. Besides, we use recent dijet data at the LHC
to give the constraints on the couplings between the colored scalars and
quarks.Comment: 21 pages,9 figures,3 tables; Version published in EPJ
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