This is a clip from a conversation with Sean Carroll from Nov 2019. Check out Sean's new book on quantum mechanics titled Something Deeply Hidden: https://amzn.to/2C6aCaf New full episodes are released once or twice a week and 1-2 new clips or a new non-podcast video is released on all other days. You can watch the full conversation here: https://www.youtube.com/watch?v=iNqqOLscOBY
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Even outside of quantum computers, some of the theories that we've been talking about, what's your hope, what's most promising to test these theories?

What are kind of experiments we can conduct, whether in simulation or in the physical world, that would validate or disprove or expand these theories?

Well, I think for, there's 2 parts of that question.

1 is many worlds and the other 1 is sort of emergent space time.

For many worlds, you know, there are experiments ongoing to test whether or not wave functions spontaneously collapse.

And if they do, then that rules out many worlds and that would be falsified.

What if there are hidden variables, there's a theorem that seems to indicate that the predictions will always be the same as many worlds.

I'm not completely, I haven't internalized it.

I haven't made it in part of my intuitive view of the world yet.

So there might be loopholes to that theorem.

Part of me thinks that there should be different experimental predictions if there are hidden variables, but I'm not sure.

But otherwise, it's just quantum mechanics all the way down.

And so there's this cottage industry in science journalism of writing breathless articles that say, you know, quantum mechanics shown to be more astonishing than ever before thought.

And really, it's the same quantum mechanics we've been doing since

Whereas with the emergent space-time stuff, we know a lot less about what the theory is.

We don't even really have a safely written down, respectable, honest theory yet.

So there could very well be experimental predictions we just don't know about yet.

That is 1 of the things that we're trying to figure out.

But for emergent space time, you need really big stuff, right?

Well, or really fast stuff, or really energetic stuff.

So there could be violations of the speed of light if you have emergent space-time.

Not going faster than the speed of light, but the speed of light could be different for light of different wavelengths.

That would be a dramatic violation of physics as we know it, but it could be possible.

The theories are just not well-developed enough yet to say.


Speaker 0: Even outside of quantum computers, some of the theories that we've been talking about, what's your hope, what's most promising to test these theories? What are kind of experiments we can conduct, whether in simulation or in the physical world, that would validate or disprove or expand these theories?

Speaker 1: Well, I think for, there's 2 parts of that question. 1 is many worlds and the other 1 is sort of emergent space time. For many worlds, you know, there are experiments ongoing to test whether or not wave functions spontaneously collapse. And if they do, then that rules out many worlds and that would be falsified. What if there are hidden variables, there's a theorem that seems to indicate that the predictions will always be the same as many worlds.

I'm a little skeptical of this theorem. I'm not completely, I haven't internalized it. I haven't made it in part of my intuitive view of the world yet. So there might be loopholes to that theorem. I'm not sure about that.

Part of me thinks that there should be different experimental predictions if there are hidden variables, but I'm not sure. But otherwise, it's just quantum mechanics all the way down. And so there's this cottage industry in science journalism of writing breathless articles that say, you know, quantum mechanics shown to be more astonishing than ever before thought. And really, it's the same quantum mechanics we've been doing since

Speaker 0: 1926.

Speaker 1: Whereas with the emergent space-time stuff, we know a lot less about what the theory is. It's in a very primitive state. We don't even really have a safely written down, respectable, honest theory yet. So there could very well be experimental predictions we just don't know about yet. That is 1 of the things that we're trying to figure out.

Speaker 0: But for emergent space time, you need really big stuff, right?

Speaker 1: Well, or really fast stuff, or really energetic stuff. We don't know, That's the thing. So there could be violations of the speed of light if you have emergent space-time. Not going faster than the speed of light, but the speed of light could be different for light of different wavelengths. That would be a dramatic violation of physics as we know it, but it could be possible.

Or not. I mean, it's not an absolute prediction. That's the problem. The theories are just not well-developed enough yet to say.

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Sean Carroll: Experimental Validation of Quantum Mechanics Interpretations and Emergent Spacetime