I've seen post-selection demonstrated in a laboratory. It definitely isn't just a philosophical construct, except inasmuch as what it says about time making peo

I've seen post-selection demonstrated in a laboratory. It definitely isn't just a philosophical construct, except inasmuch as what it says about time making people want it to be less than real, and logic doesn't work that way. As for whether you could make a PostBQP-capable computer, though.. I don't think so, at least in the most general case. I don't understand this nearly well enough to be sure, but from what I've heard, tricking causality like that has the problem that you're increasing the chance of your circuitry failing right along with the chance of getting the right result, and quantum computers are already hard enough.