Physicists create world’s first multiverse of universes in the lab

[littlebabyjesus]

I find these things tough to fully understand, but each time I see grand claims for quantum computational supremacy, the test used seems to have been specifically set up to be suited to a quantum computer - ie you ask it a question about quantum states, in this case a quantum circuit. So it can model this in a way a classical computer clearly cannot as we're talking vast Hilbert spaces of possible classical states. But I'm not entirely sure what this proves. It feels like a cheat.

 

[PTK]

Ok, so we've got "proof" that at least one another universe exists. That universe has chips slightly better than ours...

Google says its new quantum chip indicates that multiple universes exist | TechCrunch

Google announced its latest quantum chip, Willow. But what really caught the industry's attention was a wild claim tucked into the blog post.

techcrunch.com

“It lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse, a prediction first made by David Deutsch”, Hartmut Neven is quoted as writing.

The “many worlds” interpretation of quantum mechanics was actually devised by Hugh Everett a few decades before David Deutsch, and it is not a “prediction”, but a hypothesis. A hypothesis that is wrong.​

 

[littlebabyjesus]

“It lends credence to the notion that quantum computation occurs in many parallel universes, in line with the idea that we live in a multiverse, a prediction first made by David Deutsch”, Hartmut Neven is quoted as writing.

The “many worlds” interpretation of quantum mechanics was actually devised by Hugh Everett a few decades before David Deutsch, and it is not a “prediction”, but a hypothesis. A hypothesis that is wrong.​

If we're being picky, it's a hypothesis that is consistent with the evidence. It can be declared ontologically extravagant, perhaps, but there are serious physicists who take it seriously.

 

[PTK]

If we're being picky, it's a hypothesis that is consistent with the evidence. It can be declared ontologically extravagant, perhaps, but there are serious physicists who take it seriously.

There are serious physicists who believe in the existence of Heaven and Hell, too. "Other worlds" is simply a belief.

 

[littlebabyjesus]

There are serious physicists who believe in the existence of Heaven and Hell, too. "Other worlds" is simply a belief.

No it's not. It is the hypothesis that the wave function does not collapse but rather that every possibility plays out in separate universes. This is consistent with the evidence.

Where do the probability amplitudes come from? That's one question to ask of it that does not have an entirely satisfactory answer, but every interpretation of QM has an aspect that is not entirely satisfactory.

 

[WouldBe]

Is that proper chips or crisps?

What if they're fries.

 

[PTK]

No it's not. It is the hypothesis that the wave function does not collapse but rather that every possibility plays out in separate universes. This is consistent with the evidence.

Where do the probability amplitudes come from? That's one question to ask of it that does not have an entirely satisfactory answer, but every interpretation of QM has an aspect that is not entirely satisfactory.

When a particular uranium nucleus decays, there is no evidence that another universe is created in which that nucleus has not decayed.

These other universes are not observable. There is no possible way of establishing that they exist. The generation of another universe in this way would violate the law of the conservation of mass/energy.

The wave function is a mathematical representation of our state of knowledge of a system, but it is not a material reality. The cat is either alive or dead; it cannot be both at the same time, and a uranium nucleus is either decayed or not decayed.​

 

[littlebabyjesus]

The various laws of conservation would appear perfectly maintained to any observer within each branch.

Thing about Schrodinger's cat is that he created the thought experiment to illustrate an uncomfortable consequence of his own equation. He wasn't totally happy with it. Nobody is.

Is it even valid to talk about a material reality? We can talk about the results of observation, but we have to admit that our prodding of the system itself produces those results. Where is the electron before it is measured, before it interacts with something else in a particular way? The answer there has to be that it exists as a cloud of mathematical probabilities. It is everywhere and nowhere. Our intuitions about space and time break down. Can anything be said to exist except as part of a relation with something else?

QM produces only probabilities when we do measurements, but the wave function itself evolves in an exact way. Which of those is the more satisfyingly 'real'?

 

[littlebabyjesus]

Personally I find the idea that we're missing dimensions appealing. The electron must 'spin' twice to return to its original state. The 4-dimensional equivalent of a sphere would do that seen in just three dimensions.

But whatever ideas you may like, one thing is inescapable - what we call material reality is not the whole picture. We are missing something. We are inhabitants of Flatland.

 

[PTK]

The various laws of conservation would appear perfectly maintained to any observer within each branch.

Thing about Schrodinger's cat is that he created the thought experiment to illustrate an uncomfortable consequence of his own equation. He wasn't totally happy with it. Nobody is.

Is it even valid to talk about a material reality? We can talk about the results of observation, but we have to admit that our prodding of the system itself produces those results. Where is the electron before it is measured, before it interacts with something else in a particular way? The answer there has to be that it exists as a cloud of mathematical probabilities. It is everywhere and nowhere. Our intuitions about space and time break down. Can anything be said to exist except as part of a relation with something else?

QM produces only probabilities when we do measurements, but the wave function itself evolves in an exact way. Which of those is the more satisfyingly 'real'?

The probabilities are there before the measurements. Once we measure, then there are certainties, rather than probabilities.



A single slit experiment is an illustration of this. We send a stream of particles through a slit in a barrier. We do not know where an individual particle will hit a screen on the other side of the barrier.



We know that it is more likely to hit in the central region of the screen, and less likely to hit off to one side. We represent our state of knowledge using probabilities. Once the particle has hit the screen, and thereby been detected, we are certain where it hit the screen. There is no longer any need to quote the probability that it will hit that spot.



Yes, it does make sense to talk of material reality. If you were to inhale a cloud of uranium atoms, it would make a material difference to the cells in your lungs if the atoms decayed and emitted alpha particles.
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