4 research outputs found
On independent permutation separability criteria
Recently P. Wocjan and M. Horodecki [quant-ph/0503129] gave a
characterization of combinatorially independent permutation separability
criteria. Combinatorial independence is a necessary condition for permutations
to yield truly independent criteria meaning that that no criterion is strictly
stronger that any other. In this paper we observe that some of these criteria
are still dependent and analyze why these dependencies occur. To remove them we
introduce an improved necessary condition and give a complete classification of
the remaining permutations. We conjecture that the remaining class of criteria
only contains truly independent permutation separability criteria. Our
conjecture is based on the proof that for two, three and four parties all these
criteria are truly independent and on numerical verification of their
independence for up to 8 parties. It was commonly believed that for three
parties there were 9 independent criteria, here we prove that there are exactly
6 independent criteria for three parties and 22 for four parties.Comment: Revtex4, 7 pages, minor correction
A (5,5) and (6,6) PPT edge state
Entangled states with a positive partial transpose (PPTES) have interest both
in quantum information and in the theory of positive maps. In
there is a conjecture by Sanpera, Bru{\ss} and Lewenstein [PRA, 63, 050301]
that all PPTES have Schmidt number two (or equivalently that every 2-positive
map between matrices is decomposable). In order to prove or
disprove the conjecture it is sufficient to look at edge PPTES. Here the rank m
of the PPTES and the rank n of its partial transpose seem to play an important
role. Until recently all known examples of edge PPTES had ranks (4,4) or (6,7).
In a recent paper Ha and Kye [quant-ph/0509079] managed to find edge PPTES for
all ranks except (5,5) and (6,6). Here we complement their work and present
edge PPTES with those ranks.Comment: 5 pages, comments welcom
Entanglement Distillation; A Discourse on Bound Entanglement in Quantum Information Theory
PhD thesis (University of York). The thesis covers in a unified way the
material presented in quant-ph/0403073, quant-ph/0502040, quant-ph/0504160,
quant-ph/0510035, quant-ph/0512012 and quant-ph/0603283. It includes two large
review chapters on entanglement and distillation.Comment: 192 page