Contra #4: nope. Landauer’s principle implicates that reversible computation cost nothing (until you’d want to read the result, which then cost next to nothing time the size of the result you want to read, irrespective of the size of the computation proper). Present day computers are obviously very far from this limit, but you can’t assume « computronium » is too.
Reading the results isn’t the only time you erase bits. Any time you use an “IF” statement, you have to either erase the branch that you don’t care about or double the size of your program in memory.
Any time you use an « IF » statement: 1) you’re not performing a reversible computation (e.g. your tech is not what minimise energy consumption); 2) the minimal cost is one bit, irrespective of the size of your program. Using MWI you could interpret this single bit as representing « half the branches », but not half the size in memory.
Reading the results isn’t the only time you erase bits. Any time you use an “IF” statement, you have to either erase the branch that you don’t care about or double the size of your program in memory.
Any time you use an « IF » statement: 1) you’re not performing a reversible computation (e.g. your tech is not what minimise energy consumption); 2) the minimal cost is one bit, irrespective of the size of your program. Using MWI you could interpret this single bit as representing « half the branches », but not half the size in memory.