  Recently relativistic quantum information has received considerable attention
due to its theoretical importance and practical application. Especially,
quantum entanglement in non-inertial reference frames has been studied for
scalar and Dirac fields. As a further step along this line, we here shall
investigate quantum entanglement of electromagnetic fields in non-inertial
reference frames. In particular, the entanglement of photon helicity entangled
state is extensively analyzed. Interestingly, the resultant logarithmic
negativity and mutual information remain the same as those for inertial
reference frames, which is completely different from that previously obtained
for the particle number entangled state.
