Quantum information processing in the neighborhood of a black hole

Using an imperfectly prepared state, we show that in relativistic settings, the evolution of a massive spin-1/2 particle violates many standard assumptions made in quantum information theory, including complete positivity. Unlike other recent endeavors in relativistic quantum information, we are able to quantify and maximize how much information can be transferred through such a quantum process by calculating its scope. We show that, surprisingly, relativistic noise can increase the amount of information that can be transferred, and in fact, even if the initial state is arbitrarily close to the completely mixed state, information can still be transferred perfectly. Additionally, we explore the relativistic effects of velocity and gravity on quantum information processing, and we briefly discuss how quantum computation is affected by general relativity. In particular, we show that the large Wigner rotation caused by a black hole as described in the Schwarzchild metric can greatly increase the informatic content of a qubit.