Relativistic Bell Test within Quantum Reference Frames

A still widely debated question in the field of relativistic quantum information is whether entanglement and degree violation Bell's inequalities for massive particles are frame independent or not. At core this effect that spin gets entangled with momentum freedom at velocities. Here, we show a pair can be maximally violated special-relativistic regime, even without any postselection particles. To end, use methodology reference frames, which allows us to transform problem rest particle, whose state superposition momenta from viewpoint laboratory frame. We that, when relative motion two noncollinear, optimal measurements involve ``coherent Wigner rotations.'' Moreover, choice Our results open up possibility extending entanglement-based communication protocols regimes.