Entanglement map · Established

The cross norm and realignment criterion

Proved, with a source.

For a separable state, the singular values of a realigned density matrix sum to at most 1. The test is easy to compute. It is necessary for separability but not in general sufficient.

Connections

• Part of: Detection

Sources

• Further results on the cross norm criterion for separability. O. Rudolph, 2002.
• A matrix realignment method for recognizing entanglement. K. Chen, L.-A. Wu, 2002.

Checked 2026-10-30.