“Schrödinger’s Zombie: Adam Brown at the 6th FQXi Meeting”, 2019-09-08 (; similar):
Forget the cat: what if you put a computer into the Schrödinger thought experiment? You could make the computer both run and not run, at once, and that’s just a warm-up. You could, in fact, make it not run and nonetheless extract the answer to a computation. The computer will be sitting there waiting for someone to press “Run”, yet will have produced a result. It sounds impossible by definition, but that’s quantum physics for you. This idea of counterfactual computation is not just a thought experiment; there are computers in the physics labs of the world that have done this.
At the recently concluded FQXi meeting in Tuscany, Adam Brown of Stanford University grabbed hold of counterfactual computation and ran with it. What if the computer is set up to perform a brain simulation? You could ascertain what that brain would be thinking even if it is not, in fact, thinking. Whether a simulated brain is conscious is a contentious question, but suppose it is. Then you could create a mind that acts in the world, yet lacks first-person experience—a philosophical zombie. What is more, you can decide the circumstances under which the mind will be conscious or not; it might revel in happy sensations, but have no experience of sad ones. Brown’s talk put a new spin on old problems in the philosophy of mind and personal identity.
…Once you realize that you can interact without interacting, all manners of possibilities open up. Kwiat and his colleagues used the scheme to take microscope images of hairs, wires, and fibers without shining light on them (Physical Review A 58, 605–608, arXiv:quant-ph/9803060 1998). 1996 suggested that biologists could take x-ray images of cells without causing radiation damage (arXiv:quant-ph/9610033). Jian-Wei Pan of the University of Science and Technology of China and colleagues transmitted an image using hardly any photons. Roger Penrose of Oxford, in Shadows of the Mind, puckishly suggested that Orthodox Jews could use the system on the Sabbath to turn on a light without touching its switch…In the most astounding proposal of all, Richard Jozsa of Cambridge proposed in 1998 that you could swap the bomb for a computer (arXiv:quant-ph/9805086 1998). The particle is its on/off switch. Just as you can detect a bomb without interacting with it, you can obtain the output of the computer without running it.
…Suppose you program a computer to simulate a conscious mind. By putting this computer into an interferometer, you can predict what the mind will do without running the simulation. “Using counterfactual cognition, you can simulate what somebody’s going to do—you can predict what they’re going to do—without simulating them”, Brown said…From the outside, the counterfactual mind seems identical to the original or simulated mind. Its output is the same. From the inside, though, the difference is profound. The counterfactual mind doesn’t have an inside. It is a philosophical zombie. In the taxonomy of zombies, it is even weirder than other breeds, because not only is it not conscious, it doesn’t even exist. It remains a potentiality inside the computer, awaiting an “on” signal that never came…But Brown—in what was the most remarkable part of an already remarkable talk—made a virtue of this defect. Suppose you are simulating a mind that is making some big life decision. Such decisions are hard; with all the variables involved, you can never be sure which choice will make you happy or sad. But you can arrange the counterfactual procedure to execute only the happy outcomes and leave the sad ones unimplemented. Thus you could guarantee that any minds you conjure up will be happy. Indeed, you could apply that insight to an entire virtual universe, so that only universes that maximize the happiness of their occupants (or some other desirable outcome) were brought into existence.
Brown speculated that such a scenario bears on the problem of evil in theology. Even an omniscient creator faces a problem of prediction. If it wants to create a universe where good outweighs evil, it must, in effect, run a simulation first. But such a simulation is a universe in its own right. It seems the creator cannot avoid creating creatures that suffer. But counterfactual creation allows God to create a universe where good is guaranteed to outweigh evil.