The Quantum Physics Rabbit Hole, Part II

Last week’s article I left off on a bit of a cliffhanger, with the controversial idea of superposition. This week we’ll be trying to get to the bottom of what this theory actually is and what its conclusions tell us about quantum mechanics – and the rest of the physical world.

I’m going to open this with a disclaimer.

I spent a long time – a long time – researching this concept. Looking at articles (both layman and academic), wrapping my head around the math, asking ChatGPT specific questions, etc. The only thing I didn’t do is talk to a Physics PhD, which I’d certainly be up to if any human is willing to spend 4 hours going through the same theoretical questions over and over.

Never – not once – did I get a straight answer as to why we believe in superposition over any other idea.

As a reminder, wave-particle duality is a conclusion that we come to after looking at the double-slit experiment. The electrons are hitting the detector screen like particles, but are making a wave-interference pattern, meaning that somehow – somehow – they are acting like waves without actually being waves.

Why is this so impossible?

Waves are very different from particles, in the case that waves can split up once they hit a zone, such as a split. Such like:

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If you’ve ever seen waves of water, you know they can do this. Disturb the surface of a pool and the waves will multiply as they hit barriers on the way. Sure enough, this phenomenon gives us the exact pattern we end up seeing on the detector screen.

Now, if we looked at the detector screen and saw that, for every electron we shot at the slit, we got two half-electrons landing at the exact time at different parts of the screen, this would be an open and shut case. We were wrong about the way electrons operated, yadda yadda, quantum physics makes sense again.

But that’s not what happens.

Instead, we do just get one particle hitting at the wall. It’s the pattern of all subsequent electron particles that make this wave interference pattern. This seems to imply that the electrons are doing something more along the lines of:

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But why? Why are they curving, and why is it making an exact wave interference pattern? Why does Electron 2 seem to know where Electron 1 went, and be interfered by it, despite getting shot out the gun way later?

There’s a few theories as to why exactly this works. One of the more popular theories is that of the Copenhagen Interpretation, which states that (and this is where I might start getting stuff wrong if I haven’t already) the electrons are moving in a probabilistic distribution. This interpretation rules out the idea that the electrons are directly influencing each other, and rather just have the percentage chance of hitting either Spot 1 or Spot 2 at any given time. It also helps reduce the superposition paradox slightly, as the electrons need not be waves to do this – they’re just particles with a really weird sense of probability.

There’s two issues with this. One is that probabilistic thinking in science is a big no-no – “God doesn’t roll dice” etc. etc. – but I don’t really see this as an impossibility in the same way that the paradox is, so I don’t really mind it. The other issue is much bigger.

Erwin Schrodinger – a man who had a lot to do with quantum physics at this time – created a function that could predict where electrons would hit the detector screen before they did it. Remember Part I, where we said a big problem with all this is that we just couldn’t see what the electrons were doing? Well, Schrodinger guessed that, while not optimal, we could try to mathematically predict the electrons and use that as “proof” of what the electrons were doing. Sure enough, he was able to fix an equation that guessed the final distribution of the electrons almost perfectly, no matter how many slits were involved.

The problem? All Schrodinger did was take the existing functions of waves, and realign them to work in a quantum environment.

Having a probabilistic distribution that coincidentally looks like a wave pattern is one thing. But to take all the mathematics – the mechanics of waves, how they work, how they interact with one another, how they deal with barriers – and to have it work more or less right out of the box seems to imply that yes, they are in fact waves. They are waves and particles at the same time. We are so fucked.

To make matters worse, there are other experiments and applications beyond the double-slit experiment, and they all assume that the electrons follow a wave pattern, and they all just work! Take transmission electron microscopy (TEM), which is our main method of seeing things that are really tiny. The way it works is basically just spraying electrons at something and having the waves of the electrons create an image, similar to something like LIDAR. And that’s exactly what they do!

So we seem to be at an impasse. Electrons clearly have both wave and particle behaviors, and the only way to explain this that we know is superposition, meaning that the electrons are in all places at once but only end up in one place once they hit the screen. This is an admittedly stupid idea, and hence why it is called a paradox. There are a few interesting “solutions” to this paradox – some reasonable and some arguably more insane. Some of the notable ones are:

• The Aharonov-Bohm Effect: Electrons are particles, but they emit an electromagnetic wave as they move. In this case, you can think of the electromagnetic “shell” of the electron as a wave, and the electron itself as a droplet in that wave. This explains the probabilistic nature of the electron while also explaining why it follows wave behavior so well – however, it has not yet been proven.
• The Many-Worlds Interpretation: Many-Worlds isn’t taken very seriously, but it’s become a mainstay in fiction and pop culture interpretations on quantum physics. The idea is that, when the electron is shot, there is a different universe created for every potential path the electron could go down, and the spot where the electron hits tells you which world you are in. It’s a theory that’s great for writing time-travel stories, but not so much for explaining reality.
• String Theory: Ah yes, String theory – a theory arguably as well-known and controversial as quantum physics itself! String theory is a whole different can of worms, but in the context of what it means for our superposition paradox, it essentially states that electrons are more elongated – i.e. “stringy” – than standard particles. This stringiness allows them to work like a wave, but still keeps them constricted enough that, to us, they appear to just land in one place.

At the end of the day though, the truth behind superposition – and quantum theory in general – is very boring: we just don’t know. There is a way for electrons to behave like waves and particles and not be in every place at once, but our feeble brains just don’t understand it yet. Hell, maybe there is a way for particles to be every place at once, but once again we don’t understand it. Maybe a breakthrough regarding this will happen in our lifetimes, and maybe not. But we have time on our side: quantum physics was only discovered around 75 years ago, which is incredibly young by science standards. We have a long way to go!

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