Galilean covariance of a reduced density matrix
Paweł Caban, Kordian A. Smoliński, Zbigniew Walczak
We consider a system of two spin-s particles. We show that the reduced density matrix of this system obtained by tracing out over momentum is invariant under Galilean boosts and translations, and covariant under rotations. It implies that the spin entanglement of the system is the same for all Galilean observers.
Physical Review A•Oct 21, 2003•3 citations