689 research outputs found
Entanglement of mixed macroscopic superpositions: an entangling-power study
We investigate entanglement properties of a recently introduced class of
macroscopic quantum superpositions in two-mode mixed states. One of the tools
we use in order to infer the entanglement in this non-Gaussian class of states
is the power to entangle a qubit system. Our study reveals features which are
hidden in a standard approach to entanglement investigation based on the
uncertainty principle of the quadrature variables. We briefly describe the
experimental setup corresponding to our theoretical scenario and a suitable
modification of the protocol which makes our proposal realizable within the
current experimental capabilities.Comment: 9 pages, 7 figures, RevTeX
Towards variance-matrix characterization of complementarity relations in a continuous variable system
We discuss complementarity relations in a bipartite continuous variable
system. Building up from the work done on discrete d-dimensional systems, we
prove that for symmetric two-mode states, quantum complementarity relations can
be put in a simple relation with the elements of the variance matrix. When this
condition is not satisfied, such a connection becomes non-trivial. Our
investigation is the first step towards an operative characterization of the
complementarity in a scenario that has not been investigated so far.Comment: 7 pages, 4 figures, RevTeX
A dissipative scheme to approach the boundary of two-qubit entangled mixed states
We discuss the generation of states close to the boundary-family of maximally
entangled mixed states as defined by the use of concurrence and linear entropy.
The coupling of two qubits to a dissipation-affected bosonic mode is able to
produce a bipartite state having, for all practical purposes, the entanglement
and purity properties of one of such boundary states. We thoroughly study the
effects that thermal and squeezed character of the bosonic mode have in such a
process and we discuss tolerance to qubit phase-damping mechanisms. The
non-demanding nature of the scheme makes it realizable in a matter-light based
physical set-up, which we address in some details.Comment: 9 pages, 7 figures, RevTeX4, Accepted for publication by Physics
Review
Information-flux approach to multiple-spin dynamics
We introduce and formalize the concept of information flux in a many-body
register as the influence that the dynamics of a specific element receive from
any other element of the register. By quantifying the information flux in a
protocol, we can design the most appropriate initial state of the system and,
noticeably, the distribution of coupling strengths among the parts of the
register itself. The intuitive nature of this tool and its flexibility, which
allow for easily manageable numerical approaches when analytic expressions are
not straightforward, are greatly useful in interacting many-body systems such
as quantum spin chains. We illustrate the use of this concept in quantum
cloning and quantum state transfer and we also sketch its extension to
non-unitary dynamics.Comment: 7 pages, 4 figures, RevTeX
A deeper insight into quantum state transfer from an information flux viewpoint
We use the recently introduced concept of information flux in a many-body
register in order to give an alternative viewpoint on quantum state transfer in
linear chains of many spins.Comment: 6 pages, 3 figures, RevTeX
Distributing fully optomechanical quantum correlations
We present a scheme to prepare quantum correlated states of two mechanical
systems based on the pouring of pre-available all-optical entanglement into the
state of two micro-mirrors belonging to remote and non-interacting
optomechanical cavities. We show that, under realistic experimental conditions,
the protocol allows for the preparation of a genuine quantum state of a
composite mesoscopic system whose non-classical features extend far beyond the
occurrence of entanglement. We finally discuss a way to access such mechanical
correlations.Comment: 5 pages, 4 figures, to appear in Physical Review
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