10,432 research outputs found
Entanglement dynamics during decoherence
The evolution of the entanglement between oscillators that interact with the
same environment displays highly non-trivial behavior in the long time regime.
When the oscillators only interact through the environment, three dynamical
phases were identified and a simple phase diagram characterizing them was
presented. Here we generalize those results to the cases where the oscillators
are directly coupled and we show how a degree of mixidness can affect the final
entanglement. In both cases, entanglement dynamics is fully characterized by
three phases (SD: sudden death, NSD: no-sudden death and SDR: sudden death and
revivals) which cover a phase diagram that is a simple variant of the
previously introduced one. We present results when the oscillators are coupled
to the environment through their position and also for the case where the
coupling is symmetric in position and momentum (as obtained in the RWA). As a
bonus, in the last case we present a very simple derivation of an exact master
equation valid for arbitrary temperatures of the environment.Comment: to appear in QIP special issue on Quantum Decoherence and
Entanglemen
Topics in Quantum Dynamics and Coherence for Quantum Information Processing
We outline selected trends and results in theoretical modeling of quantum
systems in support of the developing research field of quantum information
processing. The resulting modeling tools have been applied to semiconductor
materials and nanostructures that show promise for implementation of coherent,
controlled quantum dynamics at the level of registers of several quantum bits
(qubits), such as spins. Many-body field-theoretical techniques have been
utilized to address a spectrum of diverse research topics. Specifically, the
theory of decoherence and more generally the origin and effects of quantum
noise and the loss of entanglement in quantum dynamics of qubits and
several-qubit registers has been advanced. Qubit coupling mechanisms via the
indirect exchange interaction have been investigated, and quantum computing
designs have been evaluated for scalability. We outline general and specific
research challenges, the solution of which will advance the field of modeling
"open quantum systems" to further our understanding of how environmental
influences affect quantum coherence and its loss during quantum dynamics
Frozen and Invariant Quantum Discord under Local Dephasing Noise
In this chapter, we intend to explore and review some remarkable dynamical
properties of quantum discord under various different open quantum system
models. Specifically, our discussion will include several concepts connected to
the phenomena of time invariant and frozen quantum discord. Furthermore, we
will elaborate on the relation of these two phenomena to the non-Markovian
features of the open system dynamics and to the usage of dynamical decoupling
protocols.Comment: 29 pages, 8 figure
Multipartite entanglement in the Fenna-Matthews-Olson (FMO) pigment-protein complex
We investigate multipartite states in the Fenna-Matthews-Olson (FMO)
pigment-protein complex of the green sulfur bacteria using a Lorentzian
spectral density of the phonon reservoir fitted with typical parameter
estimates of the species, P. aestuarii. The evolution of the entanglement
measure of the excitonic W qubit states is evaluated in the picosecond time
range, showing increased revivals in the non-Markovian regime. Similar trends
are observed in the evolution dynamics of the Meyer-Wallach measure of the
N-exciton multipartite state, with results showing that multipartite
entanglement can last from 0.5 to 1 ps, between the Bchls of the FMO complex.
The teleportation and quantum information splitting fidelities associated with
the GHZ and W_A resource states of the excitonic qubit channels of the FMO
complex show that revivals in fidelities increase with the degree of
non-Markovian strength of the decoherent environment. Results indicate that
quantum information processing tasks involving teleportation followed by the
decodification process involving W_A states of the FMO complex, may play a
critical role during coherent oscillations at physiological temperatures.Comment: 16 pages, new figs, typo
Stability of Pairwise Entanglement in a Decoherent Environment
Consider the dynamics of a two-qubit entangled system in the decoherence
environment, we investigate the stability of pairwise entanglement under
decoherence. We find that for different decoherence models, there exist some
special class of entangled states of which the pairwise entanglement is the
most stable. The lifetime of the entanglement in these states is larger than
other states with the same initial entanglement. In addition, we also
investigate the dynamics of pairwise entanglement in the ground state of spin
models such as Heisenberg and XXY models.Comment: accepted by Physical Review A, references updated and minor change
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