2,801 research outputs found
Density Dependence of Transport Coefficients from Holographic Hydrodynamics
We study the transport coefficients of Quark-Gluon-Plasma in finite
temperature and finite baryon density. We use AdS/QCD of charged AdS black hole
background with bulk-filling branes identifying the U(1) charge as the baryon
number. We calculate the diffusion constant, the shear viscosity and the
thermal conductivity to plot their density and temperature dependences.
Hydrodynamic relations between those are shown to hold exactly. The diffusion
constant and the shear viscosity are decreasing as a function of density for
fixed total energy. For fixed temperature, the fluid becomes less diffusible
and more viscous for larger baryon density.Comment: LaTeX, 1+33 pages, 6 figures, references adde
Transition magnetic moment of Majorana neutrinos in the SSM
The nonzero vacuum expectative values of sneutrinos induce spontaneously
R-parity and lepton number violation, and generate three tiny Majorana neutrino
masses through the seesaw mechanism in the SSM, which is one of
Supersymmetric extensions beyond Standard Model. Applying effective Lagrangian
method, we study the transition magnetic moment of Majorana neutrinos in the
model here. Under the constraints from neutrino oscillations, we consider the
two possibilities on the neutrino mass spectrum with normal or inverted
ordering.Comment: 20 pages, 2 figures, accepted for publication in JHEP. arXiv admin
note: text overlap with arXiv:1305.4352, arXiv:1304.624
Entropy function and higher derivative corrections to entropies in (anti-)de Sitter space
We first briefly discuss the relation between black hole thermodynamics and
the entropy function formalism. We find that an equation which governs the
relationship between Sen's entropy function and black hole entropy, can quickly
give higher order corrections to entropy of pure (anti-) de Sitter space
without knowing the corrected metric. We also show that near horizon geometry
and the entropy function extremization is no longer required for pure (anti-)de
Sitter space. The entropy of (anti-)de Sitter space and Schwarzschild-(anti-)
de Sitter black holes together with Gauss-Bonnet terms, terms and
terms are calculated as concrete examples.Comment: 24 pages, contents improved, typos corrected, references adde
Faster-than-Clifford Simulations of Entanglement Purification Circuits and Their Full-stack Optimization
Quantum Entanglement is a fundamentally important resource in Quantum
Information Science; however, generating it in practice is plagued by noise and
decoherence, limiting its utility. Entanglement distillation and forward error
correction are the tools we employ to combat this noise, but designing the best
distillation and error correction circuits that function well, especially on
today's imperfect hardware, is still challenging. Here, we develop a simulation
algorithm for distillation circuits with gate-simulation complexity of
steps, providing for drastically faster modeling compared to
Clifford simulators or wavefunction
simulators over qubits.
This new simulator made it possible to not only model but also optimize
practically interesting purification circuits. It enabled us to use a simple
discrete optimization algorithm to design purification circuits from raw
Bell pairs to purified pairs and study the use of these circuits in the
teleportation of logical qubits in second-generation quantum repeaters. The
resulting purification circuits are the best-known purification circuits for
finite-size noisy hardware and can be fine-tuned for specific hardware error
models. Furthermore, we design purification circuits that shape the
correlations of errors in the purified pairs such that the performance of the
error-correcting code used in teleportation or other higher-level protocols is
greatly improved. Our approach of optimizing multiple layers of the networking
stack, both the low-level entanglement purification, and the forward error
correction on top of it, are shown to be indispensable for the design of
high-performance second-generation quantum repeaters
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