Sean Carroll

It's detected somewhere on the other side.

And it's just a dot.

You can't figure out that much from the dot.

But you do that many, many, many times.

And what you see is an interference pattern.

It's like a wave.

went through the two slits and waves go up and down depending on how far away they are from the target.

And so a wave going through one slit can interfere with the wave going through the other slit.

And that's what you see in the distribution of dots on the detector screen.

So

The miracle occurs when you observe which slit the electron goes through, right?

Because in the Copenhagen usual way of thinking about quantum mechanics, when you observe the electron, you collapse its wave function.

It's no longer going through both slits.

You saw it go through one or the other and magically the interference pattern goes away because indeed you changed the electron dramatically by observing which one it goes through, right?

So that's all standard stuff everyone, you know, and their mom learns that in kindergarten when they're learning about quantum mechanics.

The delayed choice quantum eraser experiment is a hilariously convoluted elaboration of that, which makes people feel bad for no good reason at all.

I actually wrote a blog post about it called The Notorious Delayed Choice Quantum Eraser, where I make fun of people who are trying to make you lose sleep because of this.

Well, they got to me.

They got it.

I know.