  It is shown that a photon with a specific frequency can be identified with
the Dirac magnetic monopole. When a Dirac-Wilson line forms a Dirac-Wilson
loop, it is a photon. This loop model of photon is exactly solvable. From the
winding numbers of this loop-form of photon, we derive the quantization
properties of energy and electric charge. A new QED theory is presented that is
free of ultraviolet divergences. The Dirac-Wilson line is as the quantum photon
propagator of the new QED theory from which we can derive known QED effects
such as the anomalous magnetic moment and the Lamb shift. The one-loop
computation of these effects is simpler and is more accurate than that in the
conventional QED theory. Furthermore, from the new QED theory, we have derived
a new QED effect. A new formulation of the Bethe-Salpeter (BS) equation solves
the difficulties of the BS equation and gives a modified ground state of the
positronium. By the mentioned new QED effect and by the new formulation of the
BS equation, a term in the orthopositronium decay rate that is missing in the
conventional QED is found, resolving the orthopositronium lifetime puzzle
completely. It is also shown that the graviton can be constructed from the
photon, yielding a theory of quantum gravity that unifies gravitation and
electromagnetism.
