  We argue that the origin of unitarity violation and information loss paradox
in our understanding of black holes (BH) lies in the standard way of doing
quantum field theory in curved space-time (QFTCS), which is heavily biased on
intuition borrowed from classical General Relativity. In this paper, with the
quantum first approach, we formulate a so-called direct-sum QFT (DQFT) in BH
space-time based on a novel formulation of discrete space-time transformations
in gravity that potentially restores unitarity. By invoking the quantum effects
associated with the gravitational backreaction, we show that the Hawking quanta
emerging outside of the Schwarzschild radius ($r_S=2GM$) cannot be independent
of the quanta that continue to be inside $r_S$. This enables the information to
be carried by Hawking quanta, but in the BH DQFT formalism, we do not get any
firewalls. Furthermore, DQFT leads to the BH evaporation involving only pure
states. This means the quantum mechanical effects at the BH horizon produce two
components of a maximally entangled pure state in superselection sector Hilbert
spaces. This construction enables pure states to evolve into pure states,
restoring unitarity and observer complementarity. Finally, we discuss how our
framework leaves important clues for formulating a scattering matrix and
probing the nature of quantum gravity.
