Entangled spinning particles in charged and rotating black holes

Spin precession for an Einstein-Podolsky-Rosen pair of spin-1/2 massive particles in equatorial orbits around a Kerr-Newman black hole is studied. Hovering observers are introduced to ensure static reference frames to measure or prepare the spin state. These observers also guarantee a reliable direction to compare spin states in rotating black holes. The velocity of the particles due to frame-dragging is explicitly incorporated by addition of velocities with respect the hovering observers and the corresponding spin precession angle is computed. The spin-singlet state is proved to be mixed with the spin-triplet by dynamical and gravity effects, thus it is found that a perfect anticorrelation of entangled states for these observers is explicitly deteriorated. Finally, an analysis concerning the different limit cases of parameters of spin precession including the frame-dragging effects is carried out.