In this model, a photon “exists” as processing running on the quantum network regardless of how it is distributed. Whether a photon’s quantum wave is just starting at a point or spread out larger than a galaxy doesn’t matter as long as it runs. What exists is neither quantum states nor physical states but processing that never stops and is in our terms, immortal. To say that a photon has wave function is to maintain the stubborn illusion that it is a thing with a wave property. In quantum realism, the photon is the quantum wave and the “particle” we see is just a view created by a physical event. We observe a particle but what creates that view is the photon quantum wave. If “all the world’s a stage”, then classical mechanics describes the stage while quantum mechanics describes what is going on backstage.
A physical realist might ask “If a photon is a cloud of instances that can go through both Young’s slits at once, which one is the photon?” The question again betrays the assumption that a photon is a constant physical thing. Physical realism supports this view but quantum theory doesn’t.
We see a photon hit a screen at a point, like a particle, but that it traveled that way is just an assumption tacked onto the facts. Knowing how a photon arrives isn’t the same as knowing how it travels. Quantum theory tells us that photons travel as quantum waves but interact as point particles. Its critics couldn’t fault this logic because there is no fault. What can travel like a wave but arrive like a point particle? The next section suggests that a processing wave can.