From David Deutsch's The Beginning of Infinity:
Take a powerful computer and set each bit randomly to 0 or 1 using a quantum randomizer. (That means that 0 and 1 occur in histories of equal measure.) At that point all possible contents of the computer’s memory exist in the multiverse. So there are necessarily histories present in which the computer contains an AI program – indeed, all possible AI programs in all possible states, up to the size that the computer’s memory can hold. Some of them are fairly accurate representations of you, living in a virtual-reality environment crudely resembling your actual environment. (Present-day computers do not have enough memory to simulate a realistic environment accurately, but, as I said in Chapter 7, I am sure that they have more than enough to simulate a person.) There are also people in every possible state of suffering. So my question is: is it wrong to switch the computer on, setting it executing all those programs simultaneously in different histories? Is it, in fact, the worst crime ever committed? Or is it merely inadvisable, because the combined measure of all the histories containing suffering is very tiny? Or is it innocent and trivial?
I'm not so sure we have the computing power to "simulate a person," but suppose we did. (Perhaps we will soon.) How would you respond to this worry?
Why? It seems to me that the reverse might well be true. Measure of random unhappiness inside the computer depends on the number of bits in a brain. Measure of random unhappiness in reality (given that humans already exist) depends on the number of bits in a "diff" between a happy brain and an unhappy one, which is probably smaller.
ETA: this comment is wrong because neurons in reality are macroscopic, so you need a lot of correlated quantum randomness to flip one of them. Please disregard.
If it happens by quantum vibrations that's true, but our brains aren't perfect, and the state they go into is somewhat random. There is a reasonable chance of becoming depressed, to the point that it's actually happened in this universe many times over.