Erwin Schrödinger was the German physicist who devised the eponymous equation that describes quantum mechanical systems and thought about a quantum cat in a box.
Quotes by Erwin Schrödinger in Time One
A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The wave [or probability] function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.