Quantum Computers are doomed all over again!

[Joy Christian]

Interesting paper but I don't see how VI.A disproves number 1. What am I missing?

Number 1 claim is that two slits interference pattern can only be explained if each particle is in a superposition of passing through slits simultaneously. In other words, the claim of 1 is that classical probability theory cannot explain it. Not so, says Ballentine: it can be explained by classical probability theory.
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[FrediFizzx]

Interesting paper but I don't see how VI.A disproves number 1. What am I missing?

Number 1 claim is that two slits interference pattern can only be explained if each particle is in a superposition of passing through slits simultaneously. In other words, the claim of 1 is that classical probability theory cannot explain it. Not so, says Ballentine: it can be explained by classical probability theory.

Sorry, I read the section again and don't see how classical probability theory explains it.
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[ben6993]

Hi Fred

I think that what you are looking for isn't there in the paper. If Ballentine could have produced the QM formula using classical conditional probabilities and Bayes formulae then he would have done so. But he has pointed to a lesser target in a refutal that the classical formula for the 2-slit is as simple as had been assumed. He is saying that the condition that slit 1 only is open is condition c1, and for slit 2 only to be open is c2, and for both slits to be open together is c3. He is saying that the relationship between c1, c2 and c3 is not straightforward.

I think Fred's question about the existence of superpositions goes to the heart of the problem. A video has Roger Penrose saying (my words) that superposition is not reality. A very recent New Scientist article has Spekkens arguing for a return of reality (which I assume would remove superpositions from reality).

That is not to say that superpositions have no place in QM as they are fundamental to QM. Superpositions are important in statistics and for example the Monty Hall issue, but they exist in the minds or calculations on paper or screen. You can calculate how likely a horse is to win a race, but the reality is found after the race when the horse either won or did not. So you need superpositions but it is wrong to assume they are a reality.

Bell experimental results are, unfortunately, now being used to imply that the reality of superpositions is confirmed.

Quantum Computers do not use reality as when a measurement is made, the calculations are over. But it should be possible to use superpositions in calculations even when you know the reality is Bertlmann's socks with no superpositions. But you do not need a Quantum Computer to do that.

Having said all that, my version of the Bell experiment results is a very exotic idea which by-passes the Bell Inequalities and gives importance to the Bell results as providing an obstacle to be circumvented.

Austin

[FrediFizzx]

Superposition is a consequence of wave action. Classical waves can have superposition so it stands to reason that quantum probability waves could have superposition also.
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[Joy Christian]

Superposition is a consequence of wave action. Classical waves can have superposition so it stands to reason that quantum probability waves could have superposition also.

Ballentine is not questioning that. You are missing his explanation that the supposition principle does not violate classical probabilities as usually claimed.

Returning to the main question you raised concerning the rationale behind the quantum computing hype, the hype is driven by the belief that quantum superposition and quantum entanglement are something non-classical. Indeed, all of the physics of the past 100 years is driven by this belief that quantum mechanics is a new discovery, revealing mystical properties that go beyond classical mechanics. But Ballentine deflates this belief. He shows that, while quantum mechanics is indeed not the same as classical mechanics, it does not require a new non-classical probability theory to understand it as usually believed, either implicitly or explicitly. This also deflates your initial question about needing a "disproof" of superposition to undermine the quantum computing hype. Ballentine provides that disproof without dismissing the phenomenon of superposition. Hence, quantum computing is a misguided hype.
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[FrediFizzx]

Superposition is a consequence of wave action. Classical waves can have superposition so it stands to reason that quantum probability waves could have superposition also.

Ballentine is not questioning that. You are missing his explanation that the supposition principle does not violate classical probabilities as usually claimed.

No problem, I got that from Ballentine OK so didn't miss it.

Returning to the main question you raised concerning the rationale behind the quantum computing hype, the hype is driven by the belief that quantum superposition and quantum entanglement are something non-classical. Indeed, all of the physics of the past 100 years is driven by this belief that quantum mechanics is a new discovery, revealing mystical properties that go beyond classical mechanics. But Ballentine deflates this belief. He shows that, while quantum mechanics is indeed not the same as classical mechanics, it does not require a new non-classical probability theory to understand it as usually believed, either implicitly or explicitly. This also deflates your initial question about needing a "disproof" of superposition to undermine the quantum computing hype. Ballentine provides that disproof without dismissing the phenomenon of superposition. Hence, quantum computing is a misguided hype.

For me, quantum mechanics is simply about probabilities and the math for it. Your last three sentences do not compute.
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[Joy Christian]

Superposition is a consequence of wave action. Classical waves can have superposition so it stands to reason that quantum probability waves could have superposition also.

Ballentine is not questioning that. You are missing his explanation that the supposition principle does not violate classical probabilities as usually claimed.

No problem, I got that from Ballentine OK so didn't miss it.

Returning to the main question you raised concerning the rationale behind the quantum computing hype, the hype is driven by the belief that quantum superposition and quantum entanglement are something non-classical. Indeed, all of the physics of the past 100 years is driven by this belief that quantum mechanics is a new discovery, revealing mystical properties that go beyond classical mechanics. But Ballentine deflates this belief. He shows that, while quantum mechanics is indeed not the same as classical mechanics, it does not require a new non-classical probability theory to understand it as usually believed, either implicitly or explicitly. This also deflates your initial question about needing a "disproof" of superposition to undermine the quantum computing hype. Ballentine provides that disproof without dismissing the phenomenon of superposition. Hence, quantum computing is a misguided hype.

For me, quantum mechanics is simply about probabilities and the math for it. Your last three sentences do not compute.

Unlike you, quantum computing scammers do not see quantum mechanics as "simply about probabilities" (of course it is not, but that is another story). They believe it is a mystical theory where an electron can exist in two states, "spin up" and "spin down", at the same time, in a "quantum superposition." Some of them (such as David Deutsch, one of the founding fathers of quantum computing) even believe that these two states of elections belong to two different, parallel universes. They call this a "qubit." If they did believe like you that quantum mechanics is simply about probabilities, then there can only be "bits" and no "qubits", which would deflate their claims of "quantum supremacy" and "exponential speed up." Everything I ever say always computes.
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[FrediFizzx]

Do you believe that probability waves exist?

[Joy Christian]

Do you believe that probability waves exist?

I don't even know what "probability waves exist" means. What exists are measurement results, or clicks of detectors, or eigenvalues of Hermitian operators.
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[FrediFizzx]

Do you believe that probability waves exist?

I don't even know what "probability waves exist" means. What exists are measurement results, or clicks of detectors, or eigenvalues of Hermitian operators.

I didn't mean exists as a physical object but exists as a mathematical object based on real physical events.
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[Joy Christian]

Do you believe that probability waves exist?

I don't even know what "probability waves exist" means. What exists are measurement results, or clicks of detectors, or eigenvalues of Hermitian operators.

I didn't mean exists as a physical object but exists as a mathematical object based on real physical events.

Sure. But it is just a mathematical tool that can be used to predict real physical events.
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[FrediFizzx]

So, you agree that probability waves exist as mathematical objects. Is that correct? If so, then we can have probability based superposition. Do you agree?
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[Joy Christian]

So, you agree that probability waves exist as mathematical objects. Is that correct? If so, then we can have probability based superposition. Do you agree?

I understand what probability is. And I understand what quantum superposition is. But what is "probability based superposition"?
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[FrediFizzx]

So, you agree that probability waves exist as mathematical objects. Is that correct? If so, then we can have probability based superposition. Do you agree?

I understand what probability is. And I understand what quantum superposition is. But what is "probability based superposition"?

It is what quantum superposition is basically. Say that the coefficients of the up and down states of the qubit are equal at 1/sqrt(2). Then there is a 50 percent probability that the qubit is either up and a 50 percent probability that it is down. Does that mean that the qubit is up and down at the same time? I don't think so.
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[Joy Christian]

So, you agree that probability waves exist as mathematical objects. Is that correct? If so, then we can have probability based superposition. Do you agree?

I understand what probability is. And I understand what quantum superposition is. But what is "probability based superposition"?

It is what quantum superposition is basically. Say that the coefficients of the up and down states of the qubit are equal at 1/sqrt(2). Then there is a 50 percent probability that the qubit is either up and a 50 percent probability that it is down. Does that mean that the qubit is up and down at the same time? I don't think so.

You are talking about two different things.

First, there is a superposition of up and down states, with, in general, complex coefficients a and b. So we have

Psi = a x up + b x down.

This is a qubit state in which up and down states exist at the same time, at least according to the quantum computing guys. To them, Psi exists and it is as real as anything else.

Second, if we want to know the probability of the qubit being in the up state, then that is equal to |a|^2, according to the Born rule. But this is a separate postulate. It is not a part of the qubit itself. The qubit would have interference terms in addition to having the potential probabilities of |a|^2 and |b|^2.

So superposition and probabilities are two different concepts. In particular, Psi =/= |a|^2 and |b|^2 only.
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[FrediFizzx]

This is a qubit state in which up and down states exist at the same time, at least according to the quantum computing guys.

Do you have a reference for that? I don't ever recall seeing that.
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[Joy Christian]

This is a qubit state in which up and down states exist at the same time, at least according to the quantum computing guys.

Do you have a reference for that? I don't ever recall seeing that.

The qubit state is written down explicitly in Mikhail Dyakonov's talk I linked above: https://www.facebook.com/michel.dyakono ... z8gFDuL0DD
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[FrediFizzx]

This is a qubit state in which up and down states exist at the same time, at least according to the quantum computing guys.

Do you have a reference for that? I don't ever recall seeing that.

The qubit state is written down explicitly in Mikhail Dyakonov's talk I linked above: https://www.facebook.com/michel.dyakono ... z8gFDuL0DD

That is not the issue. And not a good reference for "...exist at the same time". And..., is he a "quantum computing guy"?
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[Joy Christian]

Do you have a reference for that? I don't ever recall seeing that.

The qubit state is written down explicitly in Mikhail Dyakonov's talk I linked above: https://www.facebook.com/michel.dyakono ... z8gFDuL0DD

That is not the issue. And not a good reference for "...exist at the same time". And..., is he a "quantum computing guy"?

Ok. If they do not exist at the same time, then they exist at different times. What are these different times when they exist?
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[FrediFizzx]

Measurement time.
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