You've probably heard of superpositions in quantum mechanics.
In the Schrödinger's Cat scenario, the cat is said to be in a superposition of alive and dead, and we're asked to note the absurdity of a cat that is somehow both alive and dead (which isn't exactly what a superposition is, but never mind that).
Thanks to a phenomenon known as decoherence, it's not really feasible to put such a macroscopic system into the kind of superposition that's useful, the kind you can exploit. So maybe we never have to worry about such a cat.
But you might still wonder: what if some far future technology allows us to do so? There's every reason to believe it's theoretically possible. And what if we put a human into a coherent superposition? Or, as quantum computing professor Scott Aaronson suggests, upload their consciousness into a quantum computer, where we would keep it coherent?
Instead of using the macabre example where the human lives or dies, suppose they simply either see a red or blue light. And suppose you leave the experiment running for five minutes. At the end of it, the subject will report having seen only one colored light for the past five minutes.
Imagine being such a subject. Imagine seeing one light turn on and stay that way for five minutes. At the end of it, you'll have a memory of having done so. And it will be an authentic memory, right? All that time really happened.
But now switch back to being the experimenter. Are there really two subjects, each seeing one light? There are various forms of the many worlds interpretation of QM, but the modern ones suggest that worlds split only when there's decoherence. Here there is none.
From the outside, we can say (in a precise and provable way) that there was no definite state for the light or subject during those five minutes. Nothing "really" happened. But the subject will find that absurd.
Is their memory reliable? Did it "really" happen? It depends on whose perspective you take.
You don't know that you're not in some elaborate quantum experiment right now. What is real to you may not be for others who you may even one day meet.
In the Schrödinger's Cat scenario, the cat is said to be in a superposition of alive and dead, and we're asked to note the absurdity of a cat that is somehow both alive and dead (which isn't exactly what a superposition is, but never mind that).
Thanks to a phenomenon known as decoherence, it's not really feasible to put such a macroscopic system into the kind of superposition that's useful, the kind you can exploit. So maybe we never have to worry about such a cat.
But you might still wonder: what if some far future technology allows us to do so? There's every reason to believe it's theoretically possible. And what if we put a human into a coherent superposition? Or, as quantum computing professor Scott Aaronson suggests, upload their consciousness into a quantum computer, where we would keep it coherent?
Instead of using the macabre example where the human lives or dies, suppose they simply either see a red or blue light. And suppose you leave the experiment running for five minutes. At the end of it, the subject will report having seen only one colored light for the past five minutes.
Imagine being such a subject. Imagine seeing one light turn on and stay that way for five minutes. At the end of it, you'll have a memory of having done so. And it will be an authentic memory, right? All that time really happened.
But now switch back to being the experimenter. Are there really two subjects, each seeing one light? There are various forms of the many worlds interpretation of QM, but the modern ones suggest that worlds split only when there's decoherence. Here there is none.
From the outside, we can say (in a precise and provable way) that there was no definite state for the light or subject during those five minutes. Nothing "really" happened. But the subject will find that absurd.
Is their memory reliable? Did it "really" happen? It depends on whose perspective you take.
You don't know that you're not in some elaborate quantum experiment right now. What is real to you may not be for others who you may even one day meet.
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