TY - JOUR A1 - Eisert, Jens A1 - Plenio, M. B. T1 - A comparison of entanglement measures N2 - We compare the entanglement of formation with a measure defined as the modulus of the negative eigenvalue of the partial transpose. In particular we investigate whether both measures give the same ordering of density perators with respect to the amount of entanglement. Y1 - 1999 ER -