PPT separability criterion

Theorem [PPT separability criterion]: If a state 𝜚 ∈ SA ⊗ SB is separable, then 𝜚TB := (idA ⊗ TB)[𝜚] ≥ 0, where TB, is the transposition on the second subsystem of the compound system SASB.

Therefore if 𝜚TB := (idA ⊗ TB)[𝜚] is nonpositive, the state 𝜚 is entangled.

In arbitrary dimensions of the two subsystems the PPT criterion provides only a necessary but not sufficient condition for separability, i.e. in "high" dimensions there exist states that remain positive under partial transposition (PPT states) even if they are entangled.

If instead the bipartite system has dimension dAdB6, i.e., the bipartite system is of the type 22 or 23 or 32, then the PPT criterion provides a necessary and sufficient condition for separability, as follows.

Theorem: A state ϱABSASB with dAdB6 is separable if and only if ϱTBAB:=(idATB)[ϱAB]0, i.e. if and only if ϱAB is PPT.

  • A. Peres, Separability criterion for density matrices, Phys. Rev. Lett. 77(8), 1413 (1996).
  • M. Horodecki, P. Horodecki, R. Horodecki, Separability of mixed states: necessary and sufficient conditions, Phys. Lett. A 223, 1 (1996).

Category:Entanglement Category:Handbook of Quantum Information

Last modified: 

Friday, July 7, 2017 - 21:06