617 research outputs found
Structure of multipartite entanglement in random cluster-like photonic systems
Quantum networks are natural scenarios for the communication of information
among distributed parties, and the arena of promising schemes for distributed
quantum computation. Measurement-based quantum computing is a prominent example
of how quantum networking, embodied by the generation of a special class of
multipartite states called cluster states, can be used to achieve a powerful
paradigm for quantum information processing. Here we analyze randomly generated
cluster states in order to address the emergence of multipartite correlations
as a function of the density of edges in a given underlying graph. We find that
the most widespread multipartite entanglement does not correspond to the
highest amount of edges in the cluster. We extend the analysis to higher
dimensions, finding similar results, which suggest the establishment of small
world structures in the entanglement sharing of randomised cluster states,
which can be exploited in engineering more efficient quantum information
carriers.Comment: 6 pages, 8 figures, revtex4-
Experimental signature of Quantum Darwinism in photonic cluster states
We report on an experimental assessment of the emergence of Quantum Darwinism
(QD) from engineered open-system dynamics. We use a photonic hyperentangled
source of graph states to address the effects that correlations among the
elements of a multi-party environment have on the establishment of objective
reality ensuing the quantum-to-classical transition. Besides embodying one of
the first experimental efforts towards the characterization of QD, our work
illustrates the non-trivial consequences that multipartite entanglement and, in
turn, the possibility of having environment-to-system back-action have on the
features of the QD framework.Comment: 5 pages, 5 figures, Revtex4-
Extremal Quantum Correlations: Experimental Study with Two-qubit States
We explore experimentally the space of two-qubit quantum correlated mixed
states, including frontier ones as defined by the use of quantum discord and
von Neumann entropy. Our experimental setup is flexible enough to allow for the
high-quality generation of a vast variety of states. We address quantitatively
the relation between quantum discord and a recently suggested alternative
measure of quantum correlations.Comment: 5 pages, 2 figure
Generation of polarization entangled photon pairs by a single crystal interferometric source pumped by femtosecond laser pulses
Photon pairs, highly entangled in polarization have been generated under
femtosecond laser pulse excitation by a type I crystal source, operating in a
single arm interferometric scheme. The relevant effects of temporal walk-off
existing in these conditions between the ordinary and extraordinary photons
were experimentally investigated. By introducing a suitable temporal
compensation between the two orthogonal polarization components highly
entangled pulsed states were obtained
Experimental Bell inequality violation without the postselection loophole
We report on an experimental violation of the Bell-Clauser-Horne-Shimony-Holt
(Bell-CHSH) inequality using energy-time entangled photons. The experiment is
not free of the locality and detection loopholes, but is the first violation of
the Bell-CHSH inequality using energy-time entangled photons which is free of
the postselection loophole described by Aerts et al. [Phys. Rev. Lett. 83, 2872
(1999)].Comment: 4 pages, 3 figures, v2 minor correction
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