159 research outputs found
Entanglement of hard-core bose gas in degenerate levels under local noise
Quantum entanglement properties of the pseudo-spin representation of the BCS model is investigated. In case of degenerate energy levels, where wave functions take a particularly simple form, spontaneous breaking of exchange symmetry under local noise is studied. Even if the Hamiltonian has the same symmetry, it is shown that there is a non-zero probability to end up with a non-symmetric final state. For small systems, total probability for symmetry breaking is found to be inversely proportional to the system size
Factorization and Criticality in the Anisotropic XY Chain via Correlations
In this review, we discuss the zero and finite temperature behavior of
various bipartite quantum and total correlation measures, the skew
information-based quantum coherence, and the local quantum uncertainty in the
thermal ground state of the one-dimensional anisotropic XY model in transverse
magnetic field. We compare the ability of considered measures to correctly
detect or estimate the quantum critical point and the non-trivial factorization
point possessed by the spin chain.Comment: 29 pages, 8 figures. A review paper accepted for publication in the
special issue Entanglement Entropy in the journal Entrop
Quantum coherence and uncertainty in the anisotropic XY chain
We explore the local quantum coherence and the local quantum uncertainty,
based on Wigner-Yanase skew information, in the ground state of the anisotropic
spin-1/2 XY chain in transverse magnetic field. We show that the skew
information, as a figure of merit, supplies the necessary information to reveal
the occurrence of the second order phase transition and the completely
factorized ground state in the XY model. Additionally, in the same context, we
also discuss the usefulness of a simple experimentally friendly lower bound of
local quantum coherence. Furthermore, we demonstrate how the connection between
the appearance of non-analyticities in the local quantum uncertainty of the
ground state and the quantum phase transitions does not hold in general, by
providing explicit examples of the situation. Lastly, we discuss the ability of
the local quantum coherence to accurately estimate the critical point of the
phase transition, and investigate the robustness of the factorization
phenomenon at low temperatures.Comment: 7 pages, 6 figures. Title changed. Close to published versio
Remote polarization entanglement generation by local dephasing and frequency upconversion
We introduce a scheme for remote entanglement generation for the photon
polarization. The technique is based on transferring the initial frequency
correlations to specific polarization-frequency correlations by local dephasing
and their subsequent removal by frequency up-conversion. On fundamental level,
our theoretical results show how to create and transfer entanglement, to
particles which never interact, by means of local operations. This possibility
stems from the multi-path interference and its control in frequency space. For
applications, the developed techniques and results allow for the remote
generation of entanglement with distant parties without Bell state measurements
and opens the perspective to probe frequency-frequency entanglement by
measuring the polarization state of the photons.Comment: 8 page
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