Quantum Physics For the Simple-Minded

By: Bharathi Vaidhyanathan, Grade 9A

What happens when you put a cat in a box? It'll try to kill you.

Quantum mechanics has always been portrayed as one of the more difficult aspects of science. It is to science what calculus is to math. The reason it seems so baffling is because it requires one to open up to completely new concepts and, if necessary, deny everything they have learnt before. Yet this very reason is

what makes not just quantum mechanics, but science as a whole, so unbelievably interesting. What really clinches it, for me personally, is the experiments.

Schrödinger (or Schroedinger, however you choose to spell it) is a well-known name in the scientific world, especially when the conversation turns to quantum theories. To us common folk, however, he is famously known to be the innovative mind behind the thought experiment, "Schrödinger's Cat". For those of you unaware of this theory, I bring you the assistance of Google.

"a cat imagined as being enclosed in a box with a radioactive source and a poison that will be released when the source (unpredictably) emits radiation, the cat being considered (according to quantum mechanics) to be simultaneously both dead and alive until the box is opened and the cat observed."

To summarize, when you put a cat in a radioactive box that emits poison, until you open the box, the cat is both dead and alive. Ladies and gentlemen, I bring you quantum physics at it’s finest.

Common sense dictates that the cat is dead. We know that the cat is dead before we open the box. At this point, I would like to remind you that "Schrödinger's Cat" is merely a thought experiment in the field of theoretical quantum physics and that no felines were harmed. This theory was, in fact, used to explain quantum superposition, which states, in simple terms, that an atom or a photon can exist in multiple states simultaneously.

To understand this, all you really need to know is the basics of probability and the properties of light. Let me break it down.

Let us assume that we have a completely reflective medium in front of us. To our right we have a light source. Light is, in its essence, a stream of photons, so we have a photon emitter that will release a narrow stream of photon on the right. To our left, we have a series of detectors, that will beep when in contact with a photon.

We know that according to the reflective properties of light, the angle of incidence is equal to the angle of reflection. Through this we can accurately decipher exactly which detector will beep. Thus, the probability of specific detector beeping is one, and the probability of all the other detectors beeping is zero. Simple enough.

Now, we assume that the medium is only partially reflective and there is an equal chance of the photons passing through. With detectors placed all around the medium, once again we can pinpoint which detector will beep when the photons pass through. Since the probability of the photons passing through the medium and the photons being reflected is equal, the probability of the one of the detectors beeping is halved. So, if the emitter released a narrow stream of about 100 photons, you would expect half of them to pass through and the other half to reflect off the medium.

What if there was only one photon? This is where Schrödinger's theory comes into play. Until the photon hits medium the probability of it hitting one of the detectors is one. At this point it is travelling on both paths and will hit both detectors. Only when the photon comes in contact with the medium do we know whether it will pass through the medium or be reflected. In the same way, until the box is opened, the cat is both dead and alive. Simple enough.

And so to you, dear reader, I have explained quantum physics.

Absolutely fascinating in my opinion, but apparently Schrödinger would beg to differ.
Schrödinger himself was not comfortable with what the quantum theory implied and probability interpretation of quantum mechanics and wrote,

"I don't like it, and I'm sorry I ever had anything to do with it."