Quantum Mechanics

Schrödinger's Cat

Schrödinger himself found it hard to accept the probabilistic approach. He invented his famous 'Schrödinger's Cat' thought experiment to demonstrate the absurdity of the situation. In this weird experiment, Schrödinger arranged for a (live) cat to be placed in a box together with a radioactive source and a radiation detector which upon registering a radioactive decay, would cause a hammer to fall and break open a flask of deadly poison which would kill the cat immediately. The radioactive source is selected so that it has a quantum mechanical probability of 50% to decay per hour. After one hour, it is equally likely that the cat is alive or dead. According to Born's interpretation of quantum mechanics, exactly one hour after this macabre experiment began, the box would contain a cat which is neither alive or dead but rather in a mixture of these two states!

In the language of quantum mechanics, the cat's wave function is a superposition of the 'dead' and 'alive' wave functions. Schrödinger thought this made the probabilistic interpretation of his theory a nonsense! Born retorted that as soon as the lid on the box is lifted so we can observe the cat, the act of observation collapses the two possible wave functions into a single one, causing the cat to be definitely dead or alive. Despite his misgivings, Schrödinger shared the 1933 Nobel Prize in Physics with Dirac for his work on formulating new theories of quantum mechanics.

Related Laureates