30 research outputs found
Asymptotic Entanglement and Lindblad Dynamics: a Perturbative Approach
We consider an open bipartite quantum system with dissipative Lindblad type
dynamics. In order to study the entanglement of the stationary states, we
develop a perturbative approach and apply it to the physically significant case
when a purely dissipative perturbation is added to the unperturbed generator
which by itself would produce reversible unitary dynamics.Comment: 15 page
Controlling Entanglement Generation in External Quantum Fields
Two, non-interacting two-level atoms immersed in a common bath can become
mutually entangled when evolving with a Markovian, completely positive
dynamics. For an environment made of external quantum fields, this phenomenon
can be studied in detail: one finds that entanglement production can be
controlled by varying the bath temperature and the distance between the atoms.
Remarkably, in certain circumstances, the quantum correlations can persist in
the asymptotic long-time regime.Comment: 12 pages, to appear in J. Opt. B: Quantum Semiclass. Op
Unital quantum operators on the Bloch ball and Bloch region
For one qubit systems, we present a short, elementary argument characterizing
unital quantum operators in terms of their action on Bloch vectors. We then
show how our approach generalizes to multi-qubit systems, obtaining
inequalities that govern when a ``diagonal'' superoperator on the Bloch region
is a quantum operator. These inequalities are the n-qubit analogue of the
Algoet-Fujiwara conditions. Our work is facilitated by an analysis of
operator-sum decompositions in which negative summands are allowed.Comment: Revised and corrected, to appear in Physical Review
Entangling oscillators through environment noise
We consider two independent bosonic oscillators immersed in a common bath,
evolving in time with a completely positive, markovian, quasi-free (Gaussian)
reduced dynamics. We show that an initially separated Gaussian state can become
entangled as a result of a purely noisy mechanism. In certain cases, the
dissipative dynamics allows the persistence of these bath induced quantum
correlations even in the asymptotic equilibrium state.Comment: 14 pages, plain-Te
Entanglement and entropy rates in open quantum systems
We study a recent conjecture about the behavior of the quantum relative
entropy compared to the relative entropy of entanglement in open bipartite
systems. The conjecture states that, under a dissipative time-evolution, the
positive rate of change of the relative entropy will always be larger than that
of the relative entropy of entanglement. After explicitly solving a two-qubit
master equation of Lindblad type with separable and entangled stationary
states, we show that the conjecture can be violated for initial states with an
entangled asymptotic state, while it appears to be confirmed when the
asymptotic states are separable.Comment: 20 pages, 13 figure
Decoherence and entanglement degradation of a qubit-qutrit system in non-inertial frames
We study the effect of decoherence on a qubit-qutrit system under the
influence of global, local and multilocal decoherence in non-inertial frames.
We show that the entanglement sudden death can be avoided in non-inertial
frames in the presence of amplitude damping, depolarizing and phase damping
channels. However, degradation of entanglement is seen due to Unruh effect. It
is shown that for lower level of decoherence, the depolarizing channel degrades
the entanglement more heavily as compared to the amplitude damping and phase
damping channels. However, for higher values of decoherence parameters,
amplitude damping channel heavily degrades the entanglement of the hybrid
system. Further more, no ESD is seen for any value of Rob's acceleration.Comment: 16 pages, 5 .eps figures, 1 table; Quantum Information Processing,
published online, 5 July, 201