I’ve been reading a lot about massive stellar objects, degenerate matter, and how the Pauli exclusion principle works at that scale. One thing I don’t understand is what it means for two particles to occupy the same quantum state, or what a quantum state really is.
My background in computers probably isn’t helping either. When I think of what “state” means, I imagine a class or a structure. It has a spin field, an energy_level field, and whatever else is required by the model. Two such instances would be indistinguishable if all of their properties were equal. Is this in any way relevant to what a quantum state is, or should I completely abandon this idea?
How many properties does it take to describe, for example, an electron? What kind of precision does it take to tell whether the two states are identical?
Is it even possible to explain it in an intuitive manner?
If you put a cat into a box, then leave and come back sometime later and you can’t see or hear the cat (just the outside of the box), you don’t actually know if the cat is still alive or if it died while you were away.
Because of the uncertainty, the cat is considered to be in a quantum state of BOTH dead and alive.
You open the box to observe, and can see it breathing: it’s just asleep. It is no longer in a quantum state, as you can be certain that it is alive.
I’m familiar with that specific interpretation of quantum mechanics. It’s not relevant to the question, and it is a complete misinterpretation of Schrödinger’s thought experiment, both its concept and its purpose. He thought that the indeterministic view of quantum mechanics was wrong, and he used the thought experiment to demonstrate how ridiculous it is by bringing it into a macroscopic scale. It’s become a lie for children that omits many factors, like what it means to “observe or measure” a system.
Which is perfect for a ELI5!
You’re missing the essential element of this thought experiment - the poison gas canister in the box which releases the gas when an atom decays. That atomic decay is a quantum event that cannot be predicted even if one has perfect knowledge of the atom concerned, and in fact whether it has actually decayed or not only becomes real when it is measured ie observed. Thus, according to this experiment, the cat is simultaneously alive and dead at once, up until the box is opened and an observation made.
If you don’t have that atomic decay, then the cat’s health is merely unknown - it is either alive or dead, not both at once, but the scientist simply doesn’t know which.
Username checks out. Cat is definitely dead.