293 research outputs found
Factorization and Criticality in the Anisotropic XY Chain via Correlations
In this review, we discuss the zero and finite temperature behavior of
various bipartite quantum and total correlation measures, the skew
information-based quantum coherence, and the local quantum uncertainty in the
thermal ground state of the one-dimensional anisotropic XY model in transverse
magnetic field. We compare the ability of considered measures to correctly
detect or estimate the quantum critical point and the non-trivial factorization
point possessed by the spin chain.Comment: 29 pages, 8 figures. A review paper accepted for publication in the
special issue Entanglement Entropy in the journal Entrop
Extracting Information from Qubit-Environment Correlations
Most works on open quantum systems generally focus on the reduced physical
system by tracing out the environment degrees of freedom. Here we show that the
qubit distributions with the environment are essential for a thorough analysis,
and demonstrate that the way that quantum correlations are distributed in a
quantum register is constrained by the way in which each subsystem gets
correlated with the environment. For a two-qubit system coupled to a common
dissipative environment , we show how to optimise interqubit
correlations and entanglement via a quantification of the qubit-environment
information flow, in a process that, perhaps surprisingly, does not rely on the
knowledge of the state of the environment. To illustrate our findings, we
consider an optically-driven bipartite interacting qubit system under the
action of . By tailoring the light-matter interaction, a
relationship between the qubits early stage disentanglement and the
qubit-environment entanglement distribution is found. We also show that, under
suitable initial conditions, the qubits energy asymmetry allows the
identification of physical scenarios whereby qubit-qubit entanglement minima
coincide with the extrema of the and entanglement
oscillations.Comment: 4 figures, 9 page
Robustness of quantum discord to sudden death
We calculate the dissipative dynamics of two-qubit quantum discord under
Markovian environments. We analyze various dissipative channels such as
dephasing, depolarizing, and generalized amplitude damping, assuming
independent perturbation, in which each qubit is coupled to its own channel.
Choosing initial conditions that manifest the so-called sudden death of
entanglement, we compare the dynamics of entanglement with that of quantum
discord. We show that in all cases where entanglement suddenly disappears,
quantum discord vanishes only in the asymptotic limit, behaving similarly to
individual decoherence of the qubits, even at finite temperatures. Hence,
quantum discord is more robust than the entanglement against to decoherence so
that quantum algorithms based only on quantum discord correlations may be more
robust than those based on entanglement.Comment: 4 figures, 4 page
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