3,149 research outputs found
Multipartite non-locality in a thermalized Ising spin-chain
We study multipartite correlations and non-locality in an isotropic Ising
ring under transverse magnetic field at both zero and finite temperature. We
highlight parity-induced differences between the multipartite Bell-like
functions used in order to quantify the degree of non-locality within a ring
state and reveal a mechanism for the passive protection of multipartite quantum
correlations against thermal spoiling effects that is clearly related to the
macroscopic properties of the ring model.Comment: 8 pages, 6 figures, RevTeX4, Published versio
Multipartite quantum and classical correlations in symmetric n-qubit mixed states
We discuss how to calculate genuine multipartite quantum and classical
correlations in symmetric, spatially invariant, mixed -qubit density
matrices. We show that the existence of symmetries greatly reduces the amount
of free parameters to be optimized in order to find the optimal measurement
that minimizes the conditional entropy in the discord calculation. We apply
this approach to the states exhibited dynamically during a thermodynamic
protocol to extract maximum work. We also apply the symmetry criterion to a
wide class of physically relevant cases of spatially homogeneous noise over
multipartite entangled states. Exploiting symmetries we are able to calculate
the nonlocal and genuine quantum features of these states and note some
interesting properties.Comment: Close to published Versio
Correlation approach to work extraction from finite quantum systems
Reversible work extraction from identical quantum systems via collective
operations was shown to be possible even without producing entanglement among
the sub-parts. Here, we show that implementing such global operations
necessarily imply the creation of quantum correlations, as measured by quantum
discord. We also reanalyze the conditions under which global transformations
outperform local gates as far as maximal work extraction is considered by
deriving a necessary and sufficient condition that is based on classical
correlations
Equilibration and nonclassicality of a double-well potential
A double well loaded with bosonic atoms represents an ideal candidate to
simulate some of the most interesting aspects in the phenomenology of
thermalisation and equilibration. Here we report an exhaustive analysis of the
dynamics and steady state properties of such a system locally in contact with
different temperature reservoirs. We show that thermalisation only occurs
'accidentally'. We further examine the nonclassical features and energy fluxes
implied by the dynamics of the double-well system, thus exploring its
finite-time thermodynamics in relation to the settlement of nonclassical
correlations between the wells.Comment: 10 pages, 7 figures, Close to published versio
Precursors of non-Markovianity
Using the paradigm of information backflow to characterize a non-Markovian
evolution, we introduce so-called precursors of non-Markovianity, i.e.
necessary properties that the system and environment state must exhibit at
earlier times in order for an ensuing dynamics to be non-Markovian. In
particular, we consider a quantitative framework to assess the role that
established system-environment correlations together with changes in
environmental states play in an emerging non-Markovian dynamics. By defining
the relevant contributions in terms of the Bures distance, which is
conveniently expressed by means of the quantum state fidelity, these quantities
are well defined and easily applicable to a wide range of physical settings. We
exemplify this by studying our precursors of non-Markovianity in discrete and
continuous variable non-Markovian collision models.Comment: 9 pages, 4 figures. Close to published versio
Quantum work statistics of controlled evolutions
We use the quantum work statistics to characterize the controlled dynamics
governed by a counterdiabatic driving field. Focusing on the Shannon entropy of
the work probability distribution, , we demonstrate that the
thermodynamics of a controlled evolution serves as an insightful tool for
studying the non-equilibrium dynamics of complex quantum systems. In
particular, we show that the entropy of recovers the expected scaling
according to the Kibble-Zurek mechanism for the Landau-Zener model.
Furthermore, we propose that the entropy of the work distribution provides a
useful summary statistic for characterizing the need and complexity of the
control fields for many-body systems.Comment: 5 pages, 2 figure
Criticality, factorization and long-range correlations in the anisotropic XY-model
We study the long-range quantum correlations in the anisotropic XY-model. By
first examining the thermodynamic limit we show that employing the quantum
discord as a figure of merit allows one to capture the main features of the
model at zero temperature. Further, by considering suitably large site
separations we find that these correlations obey a simple scaling behavior for
finite temperatures, allowing for efficient estimation of the critical point.
We also address ground-state factorization of this model by explicitly
considering finite size systems, showing its relation to the energy spectrum
and explaining the persistence of the phenomenon at finite temperatures.
Finally, we compute the fidelity between finite and infinite systems in order
to show that remarkably small system sizes can closely approximate the
thermodynamic limit.Comment: 8 pages, 8 figures. Close to published versio
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