Notice I said "machine." You are not addressing that. You are using the word "program" in place of "machine." A program controls a machine, but imagine now a machine controlling a hydrogen atom. Could such a machine be less complex than a hydrogen atom? How? Now imagine a machine (not a program) that can control every subatomic particle, nay every quark, as well as every interaction, and is less complicated than the universe. Once again, I don't see how it's possible.
if quantum computers become practical, suddenly the uncrackable crypography of today will be worthless. Some new, currently inconceivable, way of protecting data transfers will need to be developed or there will no longer be any such thing as secure data transference.
A simulator would have to be in control of everything every motion of every subatomic particle, in control of particles coming into and going out of existence.
No, a simulator would only have to be in control of every observation made by a sentient player-character. It wouldn't need to generate particles until a sentient player-character actually made an observation looking for particles.
Then it would only need the equations necessary to generate the observations.
That does not sound like the kind of simulation that could keep an entire universe going, and it certainly doesn't sound like the kind of simulation some physicists seem to be thinking about,
"...putting a VR headset on every human on the planet would..."
Bad idea Bob, the Planet would never get past PORN.
LOL. That's probably true. Why didn't the Matrix think of that? Then Neo and the rest wouldn't have tried to escape!
The machines which generate simulations are more complex than the simulations they generate. Thus, no machine could simulate the universe.
That's a good point, except that it need not simulate the universe... merely a universe. I can simulate a universe anytime I like. With enough computing power, it could even be as complex as our universe, but a fraction of the size. Maybe our universe is merely a scaled down simulation of another universe?
I'm not sure where you went with that.
In the world of aesthetics, some answer the question "What is art?" by saying "Art is what someone says is art," which is a nod to the subjectivity of questions involving evaluation.
I suppose if you want to say "A universe is what someone says is a universe," then you may have a point.
However, I am talking about the kind of universe we mean when we talk about our own. I suppose you could define a hydrogen atom as a universe and run a simple program to model it which is more complex than the atom by some standard (ignoring the fact that subatomic particles aren't as simple as we once thought them to be),
Could a program that controls a simulation of our universe with everything in it and every event in it in real time actually be less complex than the universe itself? I don't see how.