Schrodinger's Cat

The Austrian Physicist and his Unsuspecting Cat.

Mon Jun 20, 2022

Schrodinger’s Cat

What's all this talk about this Austrian physicist and his unsuspecting cat? Though Schrodinger is best known for his contributions to the foundation of quantum mechanics, you may also have heard about Schrodinger's cat. This famous thought experiment was used by Schrodinger to illustrate some ideas in quantum physics more easily.

The experiment

This is how the thought experiment goes: a cat is locked in a steel box. The box contains a small amount of a radioactive substance and after one hour, there is an equal probability of one atom either decaying or not decaying. In other words, there is a 50% chance of the radioactive atom in the box decaying. If the atom decays, a device smashes a vial of poisonous gas, killing the cat. Until the box is opened, the atom’s wave function can exist simultaneously as two states: decay and non-decay. Thus, the cat is in a superposition of two states: alive and dead.

What does it show?

In quantum theory, quantum particles can exist in a superposition of states at the same time. These particles collapse down to a single state after they interact with other particles. However, some scientists at that time in the 1930s believed that quantum particles only collapse to a single state after being viewed by an outside observer. To refute this idea, Schrodinger designed the thought experiment. Since the experiment results in the cat being dead and alive at the same time and this state is something that is not actually observed in the real world, Schrodinger is able to show that the the quantum particles do not collapse to single state after being viewed by an observer.

Since that time, there has been lots of evidence that the collapse of the wavefunction of the quantum particles is not driven by observers alone. In fact, every interaction a quantum particle makes can collapse its state. Careful analysis shows that the Schrodinger Cat experiment would really play out as follows: as soon as the radioactive atom interacts with the device measuring the decay of the atom, it collapses from its non-decayed/decayed state into one definite state. The device either gets definitely triggered and the cat is definitely killed or the device definitely does not get triggered and the cat is definitely alive. However, both states do not happen.

We hope this post has been informative and has taught you more about a great physicist and quantum mechanics! Side note: similar to how Schrodinger tried to make ideas related to quantum mechanics easier to understand, we're trying to make learning easier here at Newtonian too! Feel free to find out more about the basics of Quantum Mechanics, the study of atoms and subatomic particles.

Varun
Subject: Quantum Mechanics

Schrodinger's Cat