My TL;DR for why I don't think the theory behind quantum computers is correct: time IS discrete but nonuniform. Like the temporal structure of block solutions on Bitcoin, the complexity between one quantum of time and the next varies. There is some crazy dude I bumped into some months back who was constantly comparing quantum phenomena to proof of work's properties as a Poisson point process. What this means is that most of the time every moment the distributed system of Bitcoin miners is running, it exists in a state akin to the unstable state that quantum physicists make a bold assumption about. Rather than being a stochastic instability, they claim there is superposition, where a system is in two or more states at the same time. They assert that "measuring it" (opening Schrödinger's box) makes it collapse. This is an incredibly naive, cover-your-eyes-and-the-world-disappears approach. It's like the Ravenous Bug-Blatter Beast of Traal, or like most human babies do with the peek-a-boo game.