I RECENTLY walked by a physics division workplace that had a sticker on it saying one thing like “Heisenberg may or may not have been here”. This is in half a nod to the quantum cat, which, whereas it’s inside a field with no observer, might be lifeless or alive. We aren’t positive till we take a look at it.
This feline thought experiment is meant to assist us visualise a deep conceptual problem in quantum mechanics: the undeniable fact that the act of observing appears to find out what state matter is in. This is because of the probabilistic nature of quantum mechanics …