1,712 research outputs found
On Reduced Time Evolution for Initially Correlated Pure States
A new method to deal with reduced dynamics of open systems by means of the
Schr\"odinger equation is presented. It allows one to consider the reduced time
evolution for correlated and uncorrelated initial conditions.Comment: accepted in Open Sys. Information Dy
Tensorial characterization and quantum estimation of weakly entangled qubits
In the case of two qubits, standard entanglement monotones like the linear
entropy fail to provide an efficient quantum estimation in the regime of weak
entanglement. In this paper, a more efficient entanglement estimation, by means
of a novel class of entanglement monotones, is proposed. Following an approach
based on the geometric formulation of quantum mechanics, these entanglement
monotones are defined by inner products on invariant tensor fields on bipartite
qubit orbits of the group SU(2)xSU(2).Comment: 23 pages, 3 figure
A class of commutative dynamics of open quantum systems
We analyze a class of dynamics of open quantum systems which is governed by
the dynamical map mutually commuting at different times. Such evolution may be
effectively described via spectral analysis of the corresponding time dependent
generators. We consider both Markovian and non-Markovian cases.Comment: 22 page
Classical tensors from quantum states
The embedding of a manifold M into a Hilbert-space H induces, via the
pull-back, a tensor field on M out of the Hermitian tensor on H. We propose a
general procedure to compute these tensors in particular for manifolds
admitting a Lie-group structure.Comment: 20 pages, submitted to Int. J. Geom. Meth. Modern Physic
Classical Tensors and Quantum Entanglement II: Mixed States
Invariant operator-valued tensor fields on Lie groups are considered. These
define classical tensor fields on Lie groups by evaluating them on a quantum
state. This particular construction, applied on the local unitary group
U(n)xU(n), may establish a method for the identification of entanglement
monotone candidates by deriving invariant functions from tensors being by
construction invariant under local unitary transformations. In particular, for
n=2, we recover the purity and a concurrence related function (Wootters 1998)
as a sum of inner products of symmetric and anti-symmetric parts of the
considered tensor fields. Moreover, we identify a distinguished entanglement
monotone candidate by using a non-linear realization of the Lie algebra of
SU(2)xSU(2). The functional dependence between the latter quantity and the
concurrence is illustrated for a subclass of mixed states parametrized by two
variables.Comment: 23 pages, 4 figure
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