I don’t disagree with this, and it’s certainly hard to argue against a self-evidently true observation like “that’s just an empirical finding about the nature of the world”. My argument instead is that it doesn’t refute the many-worlds explanation of quantum computing. One can take the position that it’s really the quantum world operating in this way that is fundamental, and that classical bits and logic gates are merely an artificially restricted subset of their quantum counterparts. The key point of quantum computers in this context would seem to be that, many worlds or not, they seem to be able to exploit the existence of the complete quantum state.
There’s an interesting paper endorsing this and the Everettian many-worlds view of quantum computing that deals with many such objections, and is freely available for download:
I don’t think this is obvious at all. This is like attributing a causal paradox to entanglement, which is not true because no information is actually being exchanged. ISTM that you can’t “borrow” computational power from these other branches (in the sense of “deprive them of it”) because they don’t actually causally interact; instead, all possible outcomes of quantum collapse exist at the same time in the multiverse, and one can then posit that the power of a quantum computer comes from the existence of the full quantum state, instead of just a decoherent part of it.
It’s a question that, by its definition, can’t ever be answered, but I think it’s reasonable to assume that macroscopic objects behave in a similar way when I am not looking and listening, as they do when I am looking and listening - insofar as ‘noise’ can be defined as the vibration of air, when a tree falls and nobody is there to hear it, it makes noise.
Any system that contains a conscious observer can be ‘boxed’ in such a way that it is not yet opened to an external conscious observer - you don’t know whether a tree fell in my garden yesterday. I know the answer, but to you, the outcome isn’t observed; the box is closed - so how is it that I know the answer?
Perhaps not, but it seems to render it extraneous. I mean, say you have a set of tools, the C-tools, and with them, accomplish a given task in a certain amount of time. Then, you get new tools, the Q-tools, with which you can accomplish that same task ten times faster. Is it really reasonable, or even all that enlightening, to suppose that the Q-tools somehow access ten copies of the C-tools to perform the task in parallel?
Thanks! I may have a more detailed look at this later, but from briefly skimming the paper, the claims made are very different from those Deutsch makes—to the extent that the author claims that “computational worlds, if they can be described at all, are not fundamental to the ability of a quantum computer to out-perform its classical counterparts”.
Actually, I think I don’t understand the purported MWI explanation of the quantum speedup well enough to really make a convincing argument one way or the other, so I’ll rescind my argument.
There are zillions of numbers that have a length of 10^10^500 digits. Some will be prime, some will be composite, and some of the latter will be the multiple of exactly two prime numbers. You gave the prime *factors *of one of them, the exact number 10^10^500. There are zillions of 2’s and 5’s that need to be multiplied together to equal 10^10^500. That’s not at all the same problem.
I was amused by finding the trivial counterexample, and was expecting you to realize that you had meant to refer to semiprime numbers rather than to composite numbers. Instead, you seem to want to insist that I’m the one making a mistake, which is less amusing.
Your actual claim, which I was addressing, was “We will never know the two prime factors of a composite 10^10^500 digit number.”
I gave the two prime factors of one such number- a specific counterexample to your claim. Why are you bringing up things that are irrelevant to your original claim? I don’t deny that other numbers with that number of digits exist, or that there exist non-prime factors of that number. Neither of those things have anything to do with the claim you made.
Both Trinopus and I got your joke. See his response. Then you had to spoil it. My claim is that you spoiled a perfectly good joke. And now are spoiling it again. Quit while you’re ahead next time.
I agree, it is not, though Deutsch may at times appear to be inferring that. However, computational parallelism isn’t necessary for a MWI interpretation of quantum computing – see below.
Yes, in some ways they are, and I frankly need to read more about Deutsch’s specific ideas, which I’m currently doing, and I need to read this paper much more closely – I have mostly just skimmed it. However, it does seem to me that you’re cherry-picking a bit. I had noticed the part that you quoted and was actually going to quote the paragraph myself, not in support or refutation of an argument but because I thought it was an interesting statement:
Computational worlds, if they can be described at all, are not fundamental to the ability of a quantum computer to out-perform its classical counterparts. While this goes against the usual informal view of many-worlds quantum computation, it is nevertheless an unavoidable conclusion of the neo-Everettian view. The computational ability of quantum computers in neo-Everett comes from elsewhere: the existence of the full quantum state, rather than one part of it …
But notice the claim that this is in support of, which comes immediately before it: “quantum computing is not parallel classical computing”.
Towards the end the paper brings the two concepts together:
We need worlds for the explanatory power of the neo-Everettian interpretation as a whole (giving us the appearance of singular cats and boxes), but for computation it is the realism of the full state that gives us the physical picture.
So perhaps one might rephrase Deutsch’s challenge thus: instead of asking where all these unseen computing resources are, ask instead “where are all these other unseen quantum states into which the wavefunction might have collapsed but didn’t?”
Because if it’s assumed that they must exist – and this is the key distinction – some form of “many worlds” seems like the unavoidable answer. Looking back at the abstract, the paper certainly sets out to introduce and defend a modified “neo-Everettian” many-worlds theory as an interpretation for QM and for quantum computation.
If you are able to take the time to read the paper in more detail, I and I’m sure many others would be interested and grateful for your opinion and any further insights you might have. I’ve learned a lot from you in past discussions.
In the double-slit experiment, if a single photon is shot, one at a time, through the double slits, after a while you would expect to see two bright areas build up on the photo-sensitive screen at the back because particles are being sent through the double slits.
This is not what happens.
Initially, bright spots appear on the photo-sensitive screen at randon where a photon hit, however, after some time a diffraction pattern builds up indicating that the photon must have somehow interfered with itself by become a wave before hitting the screen.
If photon detectors are placed just behind each slit the photons behave like particles and two distinct bright patches build up on the screen, indicating particles hit it.
When the photon detectors are switched off a diffraction pattern builds up on the screen, indicating wave-like behaviour.
If the detectors are left on but their data is not registered (i.e. not stored somewhere) knowledge of which slit the photon has gone through does not exist and, therefore, when the back screen is examined a diffraction pattern is observed.
If, on the other hand, the detector data is retained and stored then the photons do behave as particles and two bright areas are observed at the back screen, indicating particles have hit.
So it seems information is crucial here.
If the detector data is erased before looking at the back screen, a diffraction pattern will will be seen. However, if the back screen is looked at before erasing the detector data, two bright areas will be observed, indicating particles.
It does not matter how long it is until the detector data is erased, the result will be the same. It could be five minutes or a million years.
The conclusion to be drawn from this is that there is no information on the photo-sensitive screen until it is observed/measured since such information is potential information and uncertain until observed. Since the detector data no longer exists, the the information on the screen must be consistent with the current reality (i.e. a reality without the detector data), and show an interference pattern because no data is available that shows a photon was detected and now forms part of our ‘reality.’
A photon is not a particle but a ‘probability distribution’, so when encountering the two slits will be distributed through both, creating a probability wave and interfering with itself thus producing a diffraction wave at the photo-sensitive screen.
Such probability waves are not real waves but are mathematical or ‘informational’ in nature, showing that it is information, not matter, that is at the basis of reality. So ‘materialism’ is not a solution to the many questions surrounding quantum mechanics and no materialist theory can account for them.
In short, reality does not start until data is obtained from the ‘system.’
The implications of this are quite mind-boggling. For example, if you look and see a mountain, the mountain becomes part of a shared reality with everyone else. But, until the mountain is looked at the mountain can only exist as waves of probabilty depending on the current world data that exists (as in the detector data).
Whatever is observed can only be within the the constraints of what is viable but on measurement will persist and become part of our reality.
So, we live in an ‘informational’ universe, not a materialstic one (where matter is seen as the fundamental element.) It is ‘mind’ that interacts with information to produce reality. You might say we live in a kind of ‘virtual reality’ where information and mind act together to play out, as in a computer game, a reality of our choosing only restricted by what some ‘server’ somewhere allows.
It would take too long to address all that needs to be addressed in the previous post, so I’ll focus on this. You’re talking here about the delayed-choice quantum eraser experiment; however, your understanding is flawed: if you only have access to the ‘near’ detector, no interference pattern is seen, at all, ever; it’s only once you throw away a certain portion of the data, based on which detections were made at the ‘far’ end, that an interference pattern becomes visible (if no which-path information is present anymore). See, for instance, this recently-revived thread, or my discussion of the experiment linked to earlier in this thread.
Now, I’ve already alluded that you’re misunderstanding the term ‘information’ as it’s used in the technical literature. The most important point is that it’s not about what the letters say, or that somebody interprets them as saying something; rather, it’s solely about the patterns of differences between the letters (or particles, or data points, or whatever). The meaning doesn’t come into it; moreover, the information need not be known by anybody.
Again, this isn’t the right conclusion, as in point of fact, it’s false on most interpretations of quantum mechanics. Hence, what you’re saying isn’t implied by QM; it might be consistent with it, but it’s just as consistent with classical mechanics.
For instance, in Bohmian mechanics, all particles, and all detection events, always have completely definite locations, whether anybody looks or not. In many worlds, the observer splits up into seeing different experimental outcomes; there, too, what’s physically there determines what the observer sees, and not the other way around. Thus, while neither Bohmian mechanics nor many worlds may be correct, they at least show us that it’s completely consistent to talk about the world in these terms, and thus, provide us with a useful caution not to overstate our conclusions.
And furthermore, the interpretation you’re proposing is actually in conflict with QM: the Wigner’s friend-example I proposed upthread yields predictions that differ from those of normal quantum mechanics.
You should not confuse the world with the tools we use to describe it. A ball that can either be in the left or the right box is described by a probability distribution; but that doesn’t mean that’s what it is.
There are explicit theories that do, so that’s just false.
Look, I appreciate that you’re trying to ask the deep questions here. That’s a good thing. But this is a really hard topic, and you don’t have much technical training on the subject. I know, everything seems obvious when you first encounter it; and one wonders why everybody else is making such a fuss.
Now, you can just go and take this obviousness, and believe all the clever people that have studied the subject in depth and come to different conclusions than you are just talking out of their asses. Or, you can apply yourself, invest the work to really get familiar with the subject; learn the math, learn the philosophy. Then try and examine your ideas. Of course, it might be that they remain the same: you just got it right from the beginning. But I’m very confident in saying that that hasn’t happened in the history of the world as of yet.
It seems to me you are simply in denial. You want to contradict the conclusions of this experiment by clinging on to outdated notions of reality but without any grounds. The people who have conducted this experiment are the real experts and they certainly do not agree with you.
This is a very silly thing to say since information isn’t really information until someone looks at it. Information* can* exist separately from consciousness but only as a potential, however, it has to combine with consciousness to mean anything.
That’s because classical mechanics isn’t relevant here. How can classical mechanics possibly account for the fact that when the detector data is destroyed and the photo-sensitive screen is developed it shows an interference pattern, not a particle one? It means that information no longer exists about particles and the current reality has changed to reflect this by the interference pattern seen. But you have to develop the film first in order to ‘actualize’ the information. Occam’s Law is pertinent here as this interpretation is the simplest and cleanest , even if extraordinary. You’re being ridiculous, and I think you probably know it.
You just don’t get it. None of this is relevant because it is a question of information, not fanciful interpretations erected out of a need to cling onto obsolete ideas about reality. It’s not matter that is at the base of reality, it is information and matter is simply a manifestation of information. A photon is not a particle; it is a probability distribution, therefore, matter is essentially a bunch of probability waves.
The really clever people know the truth but some are still in denial because it contradicts their belief system - and yours, it seems.
If you allow a photon (particle) to enter the apparatus and en-route introduce, the possibility of a 50-50 chance of going one way or another at the end of its path, this* particle* suddenly transforms into a interference wave and stops being a particle. How did the former ‘particle’ know what had happened on its way to the end of its path? Answer: The information in the system had changed so, in effect, reality had changed, and the photon changed to reflect this. Formerly, the path was predictable so the photon did not have to do anything as there was no uncertainty. But reality changed, because the information** changed.
As I’ve told you, information has a very precise definition in technical literature. It’s given by the so-called Shannon entropy. As the wiki article says:
[
When physicists speak about something having ‘information’ or ‘knowledge’ about something else, what they mean is more specifically the mutual information—a measure of how much the two systems are correlated. This does lead to some unfortunate misunderstandings for those not conversant with the terminology, but that’s a hard thing to avoid, without all the time inventing new words.
No. What you’re missing is the concept of decoherence: that, when quantum systems interact with the environment (including things like detectors), phenomena like interference become radically suppressed, and quickly unobservable.
It’s in fact pretty simple to demonstrate this. Assume we have a quantum object that can be in either of two states (say, to stay with the familiar example, going through slit one or two in an interference experiment). Label these states |1> and |2>.
(Note, don’t worry too much about the strange arrow-brackets. They’re a convention usually adopted in modern quantum mechanics; you basically should just read them as a reminder that what’s written between them—which could be any label whatsoever—refers to a quantum object.)
Then, a generic state of the system has the form
|s> = a|1> + b|2>,
where a and b are complex numbers such that |a|[sup]2[/sup] + |b|[sup]2[/sup] = 1.
Now, say we want to know the probability of observing a certain state |o>, given that the system is in state |s>. That’s given by the Born rule:
P(o) = |<s|o>|[sup]2[/sup],
that is, the probability is given by the square of the overlap of the two vectors.
Now, in something like a two-slit experiment, we would naively expect the probability to land at a given point on the screen to be a sum of the probabilities for landing there via one slit, and landing there via the other—that is, in particular, a sum of two positive (or zero) numbers. That’s the classical story.
What we find, however, is different. The reason for this is as follows. The generic state |o> can be expanded in the basis used above, yielding
|o> = c|1> + d|2>.
Furthermore, we have that <1|1> = <2|2> = 1, and <1|2> = <2|1> = 0, which just says that these states are orthogonal—they have no overlap. Thus, the basis is an orthonormal basis.
Now, let’s calculate the probability P(o). We have that (if you’re wondering why the little arrows point sometimes in one, and sometimes in another direction, you can imagine these roughly like row- and column-vectors; the salient point is that <x|y> = <x|*|y> always yields a scalar, i.e. an ordinary (complex) number; the asterisk denotes complex conjugation, except where it denotes multiplication—sorry about that):
Here, I’ve merely used the above property of the orthonormal basis. If we then calculate the absolute square (recall that for a complex number z, |z|[sup]2[/sup] = zz[sup]*[/sup], i.e. the product of the number with its complex conjugate), we get:
Now, this is a very curious result! The first two terms are what we would have expected: two positive (or zero) numbers. They are, in fact, exactly what you’d get if you’d neglected the superposition—the sum of the probability of getting to the screen via slit 1, and getting there via slit 2.
However, the extra terms, due to involving products of complex numbers, need not be positive—they can become negative. So, this sum of probabilities is sometimes increased, and sometimes reduced, depending on the value of those extra terms. This is, of course, nothing but interference. So far, so good!
Now let’s assume that we have some which-path measuring detector. If the particle traverses slit 1, it enters into the state D[sub]1[/sub]; if it goes through slit 2, it enters the state D[sub]2[/sub]. Formulated in quantum-mechanical terms:
Here, the juxtaposition of two vectors formally denotes their tensor product; we’ll just use it as a shorthand for the combined state of two systems (particle and detector). (The part in parentheses is just a common notational simplification.)
Now, we want to calculate the probability of observing the particle in state |o>, given that the detector has made a detection as above. For this, we need two extra things: first, simply due to the fact that the two states of the detector are very high-dimensional (detectors consist of very many particles, typically) it can be shown that <D[sub]1[/sub]|D[sub]1[/sub]> and <D[sub]2[/sub]|D[sub]2[/sub]> are very, very close to one, and that <D[sub]1[/sub]|D[sub]2[/sub]> and <D[sub]2[/sub]|D[sub]1[/sub]> are very, very close to zero (the two states have near-vanishing overlap). In fact, for all practical purposes, their overlap is exactly zero.
Furthermore, we want to know the total probability to find the system in the state |o>, which is the sum of the probability of finding it in state |o> and the detector having made the detection 1, and the probability of finding it in state |o> and the detector having made the detection 2. In short:
P(o) = P(o,D[sub]1[/sub]) + P(o,D[sub]2[/sub]).
So first, we must know the state of our particle/detector system after the detection. The linearity of quantum mechanics dictates the following:
Here, I’ve done nothing but insert the decomposition of |o>, so far. But we can already read off the result: the second and third terms vanish immediately, because <1|2> = <2|1> = 0. But what about the fourth term? <2|2> = 1, so this looks like it might give a contribution.
Well, recall that we had already stipulated that, since |D[sub]1[/sub]> and |D[sub]2[/sub]> are macroscopic, we have that <D[sub]2[/sub]|D[sub]1[/sub]> = 0 to extremely good precision. So it turns out that this term vanishes as well. What are we left with?
The only nonvanishing term left is just |a[sup][/sup]c|[sup]2[/sup]. Things work out exactly the same for the probability P(o,D[sub]2[/sub]): there, the only term that’s left is |b[sup][/sup]d|[sup]2[/sup]. So we have, in total, for our probability now (drumroll please):
Now, if you’re still with me, you should recognize this as just the probability we calculated before—but without the terms responsible for the interference! Those have simply vanished.
However, at no point did we have to introduce any conscious observer whatsoever into the derivation. It’s enough for the system to couple to a system with very many degrees of freedom. In a sense, the coherence—which is responsible for the interference terms—gets ‘washed out’ across the total system, the combination of particle and detector, and thus, yields no observable effects anymore.
Indeed, after the interaction with the detector, the resulting state is entangled; thus, the detector and the particle are correlated (which is what’s typically called ‘having information about one another’). In a sense, all the quantum properties of the state are now distributed across all the degrees of freedom of the combined system of the particle and the detector, and thus, if we leave out the (which-path) detector, there’s just not enough ‘quantumness’ left in the rest, the single particle, to yield observable effects (at our detection on the ‘screen’, i.e. when we measure whether the system is in state |o>).
Consequently, such effects need no conscious observer.
The same goes for more complicated setups, such as the delayed choice experiment. The calculation is left as an exercise for the reader.
“Experts” in a scientific discipline are those who publish their research in peer-reviewed journals, not YouTube videos. Thomas Campbell is a mystic crackpot whose personal “theory of everything” is considered by the scientific community to be uninformed nonsense not really worth responding to, just like your posts on this subject. As already noted, you clearly have no understanding of quantum physics, yet continue to insult the knowledgeable posters here who do and who take the time to try to provide informed guidance. I’m not sure what you think you’re accomplishing here.
Why does every - and I mean every - math illiterate who comes here to lecture actual working scientists on math related subjects insist that out there somewhere in the depths of the Internet are real experts who know the truth that the entire world scientific community can’t figure out even though they spend literally every day of their lives dealing with the outcomes of this math?
How do expect anyone to take any claim you make seriously when you get the freaking definitions wrong? You have from your first post here. You practically scream “I DON’T KNOW WHAT I’M TALKING ABOUT” in every post, probably why nobody has ever agreed with you on anything.
There are no belief systems involved. There is just math with extremely rigorous definitions for the precise reason that the slipperiness of words allows people to justify any claims they want. You can’t do that in math. Maybe that’s exactly why you refuse to learn any.
I’ve thought about this a bit before. I think that it comes down to two things. First, non-experts like abashed, MantraPhilter et al. don’t understand how advanced and specialized science has become. They seem to think that it is much as it was like in the the first half of the 1900s (or late 1800s). Much of the basic understanding of most scientific disciplines is resolved and well-established. These days research is extremely specialized and generally very narrow. In some cases, they think that this has become dogmatic, but what they don’t understand is that it is well-established because so much has been built on top of it that verifies this understanding on a daily basis.
Second, they don’t understand the process of coming up with a scientific hypothesis and the process to investigate it. They seem to think that a hypothesis is just an idea and that such ideas can simply come from the ether. They don’t understand the process of reviewing literature and building on what has been firmly established, the process of looking for the little gaps in the literature that need to be filled in. This discussion could almost be an interesting thread itself, and if this goes anywhere I might start one because I am interested in what other people think.
BeepKillBeep, I’d be very interested in such a thread, particularly if it were to focus on what could actually be done to help these people understand the defects of their reasoning. I mean, to me, it’s just such a great waste: millions of hours of intellectual work going to waste chasing mirages, simply because nobody ever managed to give them the right tools and expertise.
But most approaches seem to just lead to a doubling-down. You tell them they’re wrong, they’ll just consider you too stupid to appreciate their genius. You tell them why they’re wrong, and precisely because they’re lacking the right tools, it has no effect at all. So what’s a good strategy here?
