88 research outputs found
A recursive approach for geometric quantifiers of quantum correlations in multiqubit Schr\"odinger cat states
A recursive approach to determine the Hilbert-Schmidt measure of pairwise
quantum discord in a special class of symmetric states of qubits is
presented. We especially focus on the reduced states of qubits obtained
from a balanced superposition of symmetric -qubit states (multiqubit
Schr\"odinger cat states) by tracing out particles . Two pairing schemes are considered. In the first one, the geometric
discord measuring the correlation between one qubit and the party grouping
qubits is explicitly derived. This uses recursive relations between the
Fano-Bloch correlation matrices associated with subsystems comprising ,
, and particles. A detailed analysis is given for two, three
and four qubit systems. In the second scheme, the subsystem comprising the
qubits is mapped into a system of two logical qubits. We show that
these two bipartition schemes are equivalents in evaluating the pairwise
correlation in multi-qubits systems. The explicit expressions of classical
states presenting zero discord are derived.Comment: 26 page
Unified scheme for correlations using linear relative entropy
A linearized variant of relative entropy is used to quantify in a unified
scheme the different kinds of correlations in a bipartite quantum system. As
illustration, we consider a two-qubit state with parity and exchange symmetries
for which we determine the total, classical and quantum correlations. We also
give the explicit expressions of its closest product state, closest classical
state and the corresponding closest product state. A closed additive relation,
involving the various correlations quantified by linear relative entropy, is
derived.Comment: 20 page
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