Issue
EPL
Volume 86, Number 4, May 2009
Article Number 40003
Number of page(s) 5
Section General
DOI http://dx.doi.org/10.1209/0295-5075/86/40003
Published online 29 May 2009
EPL, 86 (2009) 40003
DOI: 10.1209/0295-5075/86/40003

Entanglement of electron pairs extracted from a many-body system

A. Ramsak1, 2, J. Mravlje2, T. Rejec1, 2 and A. Lautar1

1   Faculty of Mathematics and Physics, University of Ljubljana - Ljubljana, Slovenia, EU
2   Jožef Stefan Institute - Ljubljana, Slovenia, EU

anton.ramsak@fmf.uni-lj.si

received 10 February 2009; accepted in final form 29 April 2009; published May 2009
published online 29 May 2009

Abstract
Entanglement of spins is analyzed for two electrons extracted from a mixed many-electron state by projecting onto the two-electron subspace. The concurrence formulae are expressed in a compact form for states with a well-defined square of the total spin projection. As an example, the thermal entanglement for a qubit pair with an anisotropic Heisenberg and the Dzyaloshinskii-Moriya interactions in an inhomogeneous magnetic field is given analytically. Remarkably, the concurrence of a pair of electrons with antiparallel spins and in a delocalised orbital state is given by the scalar product of the state with its spin-flipped state and not with the time-reversed state.

PACS
03.67.Mn - Entanglement measures, witnesses, and other characterizations.
73.21.La - Quantum dots.
03.67.Bg - Entanglement production and manipulation.

© EPLA 2009