  Recently, a bundle theoretic description of massive single-particle state
spaces, which is better suited for Relativistic Quantum Information Theory than
the ordinary Hilbert space description, has been suggested. However, the
mathematical framework presented in that work does not apply to massless
particles. It is because, unlike massive particles, massless particles cannot
assume the zero momentum state and hence the mass shell associated with
massless particles has non-trivial cohomology. To overcome this difficulty,
this paper suggests a new framework that can be applied to massless particles.
Applications to the cases of massless particles with spin-1 and 2, namely
photon and graviton, will reveal that the field equations, the gauge
conditions, and the gauge freedoms of Electromagnetism and General Relativity
naturally arise as manifestations of an inertial observer's perception of the
internal quantum states of a photon and a graviton, respectively. Finally, we
show that gauge freedom is exhibited by all massless particles, except those
with spin-0 and 1/2.
