In quantum mechanics, negativity is a measure of quantum entanglement which is easy to compute.
It is a measure deriving from the PPT criterion for separability.
can be defined in terms of a density matrix
as: where: An alternative and equivalent definition is the absolute sum of the negative eigenvalues of
is an arbitrary LOCC operation over
The logarithmic negativity is an entanglement measure which is easily computable and an upper bound to the distillable entanglement.
is the partial transpose operation and