38 research outputs found
Pairwise Quantum Correlations for Superpositions of Dicke States
Pairwise correlation is really an important property for multi-qubit states.
For the two-qubit X states extracted from Dicke states and their superposition
states, we obtain a compact expression of the quantum discord by numerical
check. We then apply the expression to discuss the quantum correlation of the
reduced two-qubit states of Dicke states and their superpositions, and the
results are compared with those obtained by entanglement of formation, which is
a quantum entanglement measure.Comment: 17pages, 8 figures,slightly improved and slightly extended
version,and added some reference
Optimal measurements to access classical correlations of two-qubit states
We analyze the optimal measurements accessing classical correlations in
arbitrary two-qubit states. Two-qubit states can be transformed into the
canonical forms via local unitary operations. For the canonical forms, we
investigate the probability distribution of the optimal measurements. The
probability distribution of the optimal measurement is found to be centralized
in the vicinity of a specific von Neumann measurement, which we call the
maximal-correlation-direction measurement (MCDM). We prove that for the states
with zero-discord and maximally mixed marginals, the MCDM is the very optimal
measurement. Furthermore, we give an upper bound of quantum discord based on
the MCDM, and investigate its performance for approximating the quantum
discord.Comment: 8 pages, 3 figures, version accepted by Phys. Rev.
Quantifying quantum non-Markovianity based on quantum coherence via skew information
Based on the nonincreasing property of quantum coherence via skew information
under incoherent completely positive and trace-preserving maps, we propose a
non-Markovianity measure for open quantum processes. As applications, by
applying the proposed measure to some typical noisy channels, we find that it
is equivalent to the three previous measures of non-Markovianity for phase
damping and amplitude damping channels, i.e., the measures based on the quantum
trace distance, dynamical divisibility, and quantum mutual information. For the
random unitary channel, it is equivalent to the non-Markovianity measure based
on norm of coherence for a class of output states and it is incompletely
equivalent to the measure based on dynamical divisibility. We also use the
modified Tsallis relative entropy of coherence to detect the
non-Markovianity of dynamics of quantum open systems, the results show that the
modified Tsallis relative entropy of coherence are more comfortable
than the original Tsallis relative entropy of coherence for small
.Comment: 13 pages, 5 figure
The one-way unlocalizable quantum discord
In this paper, we present the concept of the one-way unlocalizable quantum
discord and investigate its properties. We provide a polygamy inequality for it
in tripartite pure quantum system of arbitrary dimension. Several tradeoff
relations between the one-way unlocalizable quantum discord and other
correlations are given. If the von Neumann measurement is on a part of the
system, we give two expressions of the one-way unlocalizable quantum discord in
terms of partial distillable entanglement and quantum disturbance. Finally, we
also provide a lower bound for bipartite shareability of quantum correlation
beyond entanglement in a tripartite system.Comment: 6 pages, 3 figures. Minor corrections, references adde