The negativity<ref>quant-ph/0102117</ref> is an entanglement measure which is easy to compute.
The negativity can be defined as:
where:
-
is the partial transpose of ρ with respect to subsystem A
-
is the trace norm or the sum of the sigular values of the operator X.
An alternative and equivalent definition is the absolute sum of the
negative eigenvalues of :
where λi are all of the eigenvalues.
See also
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