5,372 research outputs found
A large-N approximated field theory for multipartite entanglement
We study the characterization of multipartite entanglement for the random
states of an -qbit system. Unable to solve the problem exactly we generalize
it, changing complex numbers into real vectors with components (the
original problem is recovered for ). Studying the leading diagrams in
the large- approximation, we unearth the presence of a phase transition
and, in an explicit example, show that the so-called entanglement frustration
disappears in the large- limit.Comment: 12 pages, 15 figure
Polarized ensembles of random pure states
A new family of polarized ensembles of random pure states is presented. These
ensembles are obtained by linear superposition of two random pure states with
suitable distributions, and are quite manageable. We will use the obtained
results for two purposes: on the one hand we will be able to derive an
efficient strategy for sampling states from isopurity manifolds. On the other,
we will characterize the deviation of a pure quantum state from separability
under the influence of noise.Comment: 14 pages, 1 figur
Chiral charge dynamics in Abelian gauge theories at finite temperature
We study fermion number non-conservation (or chirality breaking) in Abelian
gauge theories at finite temperature. We consider the presence of a chemical
potential for the fermionic charge, and monitor its evolution with
real-time classical lattice simulations. This method accounts for short-scale
fluctuations not included in the usual effective magneto-hydrodynamics (MHD)
treatment. We observe a self-similar decay of the chemical potential,
accompanied by an inverse cascade process in the gauge field that leads to a
production of long-range helical magnetic fields. We also study the chiral
charge dynamics in the presence of an external magnetic field , and extract
its decay rate . We provide in this way a
new determination of the gauge coupling and magnetic field dependence of the
chiral rate, which exhibits a best fit scaling as . We confirm numerically the fluctuation-dissipation relation
between and , the Chern-Simons diffusion rate,
which was obtained in a previous study. Remarkably, even though we are outside
the MHD range of validity, the dynamics observed are in qualitative agreement
with MHD predictions. The magnitude of the chiral/diffusion rate is however a
factor times larger than expected in MHD, signaling that we are in
reality exploring a different regime accounting for short scale fluctuations.
This discrepancy calls for a revision of the implications of fermion number and
chirality non-conservation in finite temperature Abelian gauge theories, though
not definite conclusion can be made at this point until hard-thermal-loops
(HTL) are included in the lattice simulations.Comment: 32 pages, 11 figures. V2: Improved introduction, added some
discussions and references. Corrected typos. Corresponds to published versio
Local Hamiltonians for Maximally Multipartite Entangled States
We study the conditions for obtaining maximally multipartite entangled states
(MMES) as non-degenerate eigenstates of Hamiltonians that involve only
short-range interactions. We investigate small-size systems (with a number of
qubits ranging from 3 to 5) and show some example Hamiltonians with MMES as
eigenstates.Comment: 6 pages, 3 figures, published versio
A framework for trustworthiness assessment based on fidelity in cyber and physical domains
We introduce a method for the assessment of trust for n-open systems based on a measurement of fidelity and present a prototypical implementation of a complaint architecture. We construct a MAPE loop which monitors the compliance between corresponding figures of interest in cyber- and physical domains; derive measures of the system's trustworthiness; and use them to plan and execute actions aiming at guaranteeing system safety and resilience. We conclude with a view on our future work
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