### Abstract

We study 12 parameter families of two-qubit density matrices, arising from a special class of two-fermion systems with four single-particle states or alternatively from a four-qubit state with amplitudes arranged in an antisymmetric matrix. We calculate the Wootters concurrences and the negativities in a closed form and study their behavior. We use these results to show that the relevant entanglement measures satisfy the generalized Coffman-Kundu-Wootters formula of distributed entanglement. An explicit formula for the residual tangle is also given. The geometry of such density matrices is elaborated in some detail. In particular, an explicit form for the Bures metric is given.

Original language | English |
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Article number | 505304 |

Journal | Journal of Physics A: Mathematical and Theoretical |

Volume | 41 |

Issue number | 50 |

DOIs | |

Publication status | Published - Dec 1 2008 |

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### ASJC Scopus subject areas

- Statistical and Nonlinear Physics
- Statistics and Probability
- Modelling and Simulation
- Mathematical Physics
- Physics and Astronomy(all)

### Cite this

*Journal of Physics A: Mathematical and Theoretical*,

*41*(50), [505304]. https://doi.org/10.1088/1751-8113/41/50/505304