Tuesday, November 07, 2006

Quantum Physics Debate, 1: The 'Many Worlds' Interpretation

The earlier thread on The fatalism of entropy. The dynamism of spontaneous order ended up in a discussion about the claims of the Many World Interpretation to explain the observations made in quantum physics experiments. Put simply, the claim is that each time a choice is made, a new universe springs into existence. This is meant quite literally. Brian Scurfield argued this Many World Interpretation is both real, and required to explain free will -- to which I and others objected (you can visit the thread to see that debate).

Brian wished to open a thread on which to argue directly his claims for the Many World Interpretation. This is that thread. The following is Brian's opening salvo.

The Many Worlds Interpretation is the claim that Quantum Mechanics is a true description of reality and that this description applies at all scales, from the microscopic to the macroscopic. It is the claim that not only atoms are subject to quantum phenomena but also observers such as you and me. Taken seriously, the Many Worlds Interpretation implies that physical reality is a vastly bigger thing than we perceive and that reality is partitioned into entities that to a very good approximation are classical universes identical to ours. In the Many Worlds Interpretation, other universes exist and affect each other and we can observe the results of this experimentally - for example when we carry out interference experiments.

The entire ensemble of universes in the Many Worlds Interpretation is contained in an entity called the 'multiverse.' Each universe in this multiverse obeys exactly the same laws of physics and there is an infinity of universes. Universes differ in how events turn out. When two previously identical universes become different because events turn out differently we say the universes have differentiated. The multiplicity of each identical universe in the multiverse is infinite. We can speak of the measure of each universe. Basically it is the relative proportion of one set of identical universes with respect to another set of identical universes. Measure is an important concept in the Many Worlds Interpretation - it means that things do not turn out equally. It means that our choices in the multiverse are important because they govern the future measure of ourselves. And it means that we need not be concerned about the possibility of giant Sperm Whales appearing in orbit around the Earth.

The original version of the Many Worlds Interpretation was put forward by Hugh Everett III in 1957. In its original conception, universes did not differentiate, they split. This creates a number of problems with measure and also in reconciling the MWI with existing physical law. For these reasons the idea of splitting was dropped and replaced with the idea of differentiation by freedomist physicist David Deutsch. It was Deutsch's interest in the Many World Interpretation that led him to discover the almost thaumaturgical possibility of a universal quantum computer, laying the foundation for the modern field of quantum information theory. Universal quantum computers are probably just years away from realisation.

Peter has asked "why the Many Worlds Interpretation is a meaningful physical explanation and not just a useful concept or method". My outline above hints at some reasons. In the equations of Quantum Mechanics we have a tool that describes and predicts our observations in precise detail. We are entitled, therefore, to regard these equations as telling us something about the nature of reality for where does that predictive power come from if the equations do not reflect truths about reality? When the mathematics of quantum mechanics tell us that a quantum computer can perform prodigious feats of calculation in real time by differentiating into, say, 10^1000 versions of itself, then what are we to conclude? That those 10^1000 versions are just mathematical conveniences? How are we to explain the calculation when the entire observable universe contains just 10^80 atoms?

But we don't need complicated mathematics to tell us multiple universes exist. We can infer it from a purely non-mathematical, physical argument, as David Deutsch does in Chapters 2 and 9 of his book The Fabric of Reality when he considers various single-photon interference experiments (see also this video).

Another reason to regard the Many Worlds Interpretation as an explanation is that we have begun to elucidate in detail the structure of the multiverse and how it is determined by information flow (the multiverse is rather more than just an ensemble of universes!). If the multiverse were not real, it seems inconceivable that we could do this. Furthermore, the Many World Interpretation can be used to derive the Born probability rule of Quantum Mechanics. If correct, then even this in itself indicates that the Many World Interpretation has deep explanatory power for previously the Born rule had to be assumed.

A popular criticism of the Many Worlds Interpretation is that we cannot see or communicate with other universes. We can only infer the existence of other universes from things seen in this universe. The reason for this is that interference occurs when universes that had become different become identical again. The more different the two universes have become the more unusual it is for them to come together again - although this is happening all the time. Controlling interference between two universes requires that we control all the particles that have different states in the two universes and for practical purpose this means that we can control interference only in universes that are very nearly identical. For you to communicate with your doppelgänger would require controlling an astronomical number of particles, including all those in your brain. This is not even a remote possibility. That we infer the existence of other universes indirectly should be no more controversial than that we infer the existence of, say, neutrinos indirectly. We can't be absolutely sure that neutrinos really exist, but the concept provides the best explanation for things we do observe.

Another popular criticism of the Many Worlds Interpretation is that it cannot be distinguished from the philosophically lame Copenhagen Interpretation, which is another popular scientific explanation for the observations of quantum experiments. But the criticism may not stand. David Deutsch proposed the first test to distinguish the Many World Interpretation from the Copenhagen Interpretation in 1977 (see Quantum Concepts of Space and Time, Oxford: The Clarendon Press, pp. 204-214) and there have been a number of other proposals put forward since then. Unfortunately these are not yet technically feasible (and some may be conceptually wrong), but we should not be surprised that the Many World Interpretation makes different predictions to its rivals for it has different assumptions.

I'll quickly summarise some other reasons why you should regard the Many Worlds Interpretation as an explanation. In the Many World Interpretation, a particle is a particle; it is not both localized at a point and spread out over the whole universe. Explanations that invoke the latter idea have only ever caused confusion! The Many Worlds Interpretation does not require "spooky action at a distance" or that, in Einstein's words, "God plays dice." Quantum mechanics turns out to be, after all, local and deterministic, as all good explanations are. In the Many World Interpretation, reality exists independently of consciousness and although we are differentiating into countless versions all the time we can reconcile this with identity and free will. Finally - as implied by the other points - the Many Worlds Interpretation requires no collapse of the wave function (the wave function doesn't even seem to collapse in the Many World Interpretation) so this postulate can be dropped from quantum mechanics and Ockham's Razor slices in favour of the Many Worlds Interpretation.

The Many Worlds Interpretation is not without possible non-trivial problems. But these problems are not obvious objections stemming from incredulity to the whole idea of multiple universes, they are technical problems (and some [pdf] may already have been resolved). The Many World Interpretation has matured [pdf] in the last two decades and many critics have not caught up. We need to think what it would mean if the Many Worlds Interpretation were true, for so far it is our only tenable explanation of the strange quantum reality that we observe.

Feel free to either comment below, or to send me your own substantive five-hundred word response for publication here later in the week.

UPDATE:
As Falufulu Fisi suggested, I have re-posted Mark Sadgrove's substantive comment below as number two in this series. You can find it here:
Quantum Physics Debate, 2: The Many Worlds Interpretation rebutted - Mark Sadgrove, at Not PC

LINKS:
The fatalism of entropy. The dynamism of spontaneous order - Not PC [thread]
Many Worlds Interpretetation - Wikipedia
Advances in reserch - Hitachi Global
Hugh Everett bio - MIT
David Deutsch - Wikipedia
Quantum computer - Wikipedia
Quantum computers: march of the Qbits - New Scientist
Shor's algorithm - Wikipedia
'The Fabric of Reality,' by David Deutsch - Qubit.Org [book review]
Lecture 2: Interference - David Deutsch video lectures [video lecture]
The structure of the multiverse - David Deutsch
Quantum theory of probability and decisions - David Deutsch
The Quantum Aristotle - Peter Cresswell, SOLO
Copenhagen Interpretation - Wikipedia
An extension of 'Popper's Experiment' can test interpretation of quantum mechanics - R.Plaga
The wave function "does not seem to collapse" - 'Fabric of Reality' message board
The basis problem in Many World Theories - Henry P. Stapp [21-page PDF]
There is no basis ambiguity in Everett quantum mechanics - Mark A. Rubin
100 years of the Quantum - Tegmark & Wheeler [9-page PDF]

RELATED: Philosophy, Science
, Ethics

55 Comments:

Blogger Brian S said...

I would like to correct a point in PC's introduction. He wrote that "[p]ut simply, the claim is that each time a choice is made, a new universe springs into existence."

Most Many Worlders would not in fact claim that and it is not my claim. As I explain in my post, the idea of splitting has been replaced with the idea of differentiation. Universes are not created at each decision alternative, rather previously identical universes differentiate from each other.

As I also explain, there are an infinite number of each identical universe (the multiplicity of each identical universe is infinite). Because such universes are exactly identical, they are said to be fungible.

Another example of something that is fungible is money. A dollar in your bank account is fungible with a dollar in my bank account. We can interchange the dollars but because the dollars represent exactly the same thing, nothing has changed. There is such a thing as one dollar, but every dollar in New Zealand is fungible with every other dollar. One cannot label a particular dollar and say this is the *real* dollar. Similarly with fungible universes. For this reason we have to identify ourselves with every identical version of ourselves in a set of identical universes. We cannot point to one version and say this is the real me.

11/27/2006 05:24:00 am  
Blogger Berend de Boer said...

We truly have reached the end of science if utter speculation is now the main subject of scientist.

But it makes for good science fiction.

11/27/2006 08:38:00 am  
Blogger Brian S said...

Did you actually read the post Berend? If Many Worlds is utter speculation, then how was it that Deutsch's pursuit of this idea led him to the discovery of universal quantum computers? And what is your explanation for how Shor's algorithm works?

I have given you lots of reasons why the Many Worlds Interpretation is the only tenable explanation so far for all the quantum phenomena we observe, and I have given you links that show how you can arrive at the "many worlds" conclusion through a simple chain of reasoning based on single-photon interference experiments. The commonsense idea that there is only one universe is wrong and it is that people are so wedded to the idea of one universe that leads to so much confusion and philosophic nonsense in quantum physics.

Albert Einstein could not accept that quantum mechanics is a complete description of reality because he (rightly) distained "spooky action at a distance" and fundamental stochasticity ("God does not play dice") and it is stunning to read in the famous Einstein-Podolsky -Rosen paper how close the authors come to the idea of multiple universes. For example, in this passage:

Starting then with the assumption that the wave function does give a complete description of the physical reality, we arrived at the conclusion that two physical quantities, with noncommuting operators, can have simultaneous reality.

!

Instead of seeing what this implies, EPR concluding that this is evidence that quantum mechanics is incomplete. Our commonsense idea that there is only one universe can really blind us.

11/27/2006 11:10:00 am  
Blogger Rebel Radius said...

I’m the other half of RebelRadius, so I guess I could be RebelCircumference, with a PhD in physics, so I’ve some beginning of an understanding of quantum mechanics which has been enlightened by studying under some excellent practitioners in this area.

The text itself is a good explanation of the MWI (Many Worlds Interpretation), which to explain anything in the area of quantum mechanics in English and it still to remain accurate is extremely hard to do. So much of this field, read 99%+, can only be described using some rather complex maths. It is only by understanding the maths that you truly get an understanding of the concepts.

The MWI interests me from a long time ago from it being used as a plot device in science fiction, but on being exposed to the science behind it I have my doubts on it being a valid interpretation. It does avoid some of the complexities of things like wave function collapse and wave-particle duality which do not seem to make any sense when using just the English explanations of what is happening, however when you start to understand the mathematics behind it, the apparent illogicalities are logical.

For the idea of MWI allowing free will, yes, it does explain how for the universe you are now in you have selected it, but is it really free will when for every quantum event you will have selected all possible routes? To my understanding, this means far from having free will, you must take every possible route.

For the moment, MWI, along with several other explanations, seem to be potentially consistent with reality. The mathematics around each model can be mathematically correct and internally consistent, however this need not mean that they describe the physical reality.

This is very similar to some other ideas in quantum mechanics, like string theory, which can be incredibly elegant mathematical models of reality that may or may not correspond to physical reality.

I eagerly await future developments in this field as I see what I studied at university become more and more outdated, a bit like an astronomy book I own from the late 1800’s, which ponders how the sun is powered. It has calculations on how much coal is being burned and how long it will last, with confusion on how this does not quite match the predicted age of the universe as the coal should have run out long ago.

11/27/2006 11:57:00 am  
Anonymous Falafulu Fisi said...

Brian S said...
[As I explain in my post, the idea of splitting has been replaced with the idea of differentiation.]

Brian, you've quoted in the other thread that NO SPLITTING is taking place, but PRE-EXISTING multiple unverses. It means that they were there already, which to sum it up, they had no beginning or no Big Bang. So, if this is the case, then how MWI fits in with General Relativity (GR) ? The Big Bang and the origin of time & space is a consequence of GR. Are you saying that the PRE-EXISTING multiple unverses were there before the Big Bang and when the Bang started creating our own universe, then somewhere along the line it (our universe) evolves itself to become parallel to those pre-existing multiple universes?

you also said...
[Because such universes are exactly identical]

Could you clarify, your meaning of 'identical' here? I mean that the Copenhagen Interpretation (CI) of Quantum Mechanics, does explain & have demonstrated by experiment of 'Teleportation' phenomena, where physical properties (operators for momentum, spin, energy, etc,...) of a particle in room 'A' has been teleported to a another particle in another physical separable room 'B'. This said that both particles 'A' & 'B' are IDENTICAL. This is my question. BTW, the team members that did this experiment was the same ones who 'confirm the non-local universe' in a paper that I posted a link to in the other thread.

If you answer that it means identical in all their (other universes) physical states, ie, operators for momentum, spin, energy, etc, of each particles), can you point out of how or where MWI has derived this identical phenomena.

11/27/2006 01:38:00 pm  
Blogger Eric Olthwaite said...

"As I explain in my post, the idea of splitting has been replaced with the idea of differentiation. Universes are not created at each decision alternative, rather previously identical universes differentiate from each other."

Oh come on Brian, that's just differentiating hairs.

11/27/2006 01:45:00 pm  
Anonymous Falafulu Fisi said...

Brian S said...
[I have given you links that show how you can arrive at the "many worlds" conclusion through a simple chain of reasoning based on single-photon interference experiments.]

Now, can you explain of how MWI invoke the interference from other universes, because , this is a violations of property rights of this universe if particles from other universes just pop-in uninvited to our universe everytime there is a single-photon interference experiment is performed in our backyard. So, a brief explanation from you regarding the interpretation of MWI about the single-photon example, would be good.

Can you also account if MWI say anything of how particles of our Universe can do the same by interfering in events ( experiments) in other universes, by entering their universe uninvited?

11/27/2006 01:47:00 pm  
Anonymous Anonymous said...

Wow... an introduction to quantum physics by someone who obviously knows very little about it... fascinating.

But I guess if real knowledge was a requirement for an opinion then most bloggers would be out of a hobby, I guess.

11/27/2006 02:02:00 pm  
Blogger PC said...

Wow...another anonymous comment providing yet more evidence of the vacuity of anonymously-posted comments.

11/27/2006 03:17:00 pm  
Anonymous Falafulu Fisi said...

MWI proposals...
[Unfortunately these are not yet technically feasible (and some may be conceptually wrong), but we should not be surprised that the Many World Interpretation makes different predictions to its rivals for it has different assumptions.]

That is exactly why it has to be dismissed. If it is technically not feasible, it can never be TESTED. The reason, that it can never be TESTED is because of the non-interactions amongst many universes. This is similar to proving GOD. There is no way to prove that there God exist as the notion of GOD does not physically interact with our universe.

MWI will only be testable if the notion of GOD could be tested physically.

11/27/2006 06:12:00 pm  
Blogger Brian S said...

FF -

Most people have the idea that only the present moment is real, that past moments no longer exist, and that futures moments are yet to be. We know from General Relativity that this commonsense view is wrong. Things that happen in the same moment for you may not happen in the same moment for me if our reference frames differ. For example, you and I may disagree about when two balls hit the ground. Depending on how we are moving with respect to each other, and where we are, then I might maintain that the two balls hit the ground simultaneously while you might maintain that they hit the ground one after the other. So for you and I, the present moment does not have the same content. These two viewpoints are not inconsistent, it is just that each of us partitions space-time into moments differently.

In General Relativity, then, there is the idea of space-time and we partition space-time into moments according to our reference frame (similarly, we can slice a loaf of bread many ways). Space-time exists eternally. Moments are not created or destroyed. They just are. It is the same in the multiverse - just that there are a hell of a lot more moments! In this conception of things, the Big-Bang is, to quote Julian Barbour, "just another card in the deck".

11/27/2006 10:51:00 pm  
Anonymous Falafulu Fisi said...

Brian,

I asked you question about a horse, you then answered back my question about a donkey.

I am not gonna move forward, to ask my next question in this debate, if you're EVASIVE.

Now answer the questions, and don't obfuscicate.

Did the other Multiple Universes had a beginning or not? YOU CLAIMED in the other thread, that they're all pre-existing universes differentiating themselves, when you denied that they are not splitting.

- How did they originate?
- Did they have a beginning or not?
- If they had a beginning in the Big Bang, why didn't General Relativity (GR) predict those parallel universes in its formulations, since all the predictions of GR has been so far been confirmed experimentally.

your said...
[Space-time exists eternally.]

WRONG... Space-time had a beginning when the Big Bang started. Anything that had a beginning is not eternal. To ask a question such as what was time or space before Big Bang is irrelevant because, space & time were created at the moment of the BANG. What on earth is this? You must stop playing with words, and try to dig into the physical realities that we debating here.

11/27/2006 11:11:00 pm  
Anonymous Falafulu Fisi said...

Brian S said..
[In the Many Worlds Interpretation, other universes exist and affect each other and we can observe the results of this experimentally - for example when we carry out interference experiments.]

Brian, you've got to be joking here. Where in the page for the double slit experiment you quoted (see link below) that say, the result confirmed the existence of Multiple Universes.

"Double-Slit"
http://www.hqrd.hitachi.co.jp/em/doubleslit.cfm

It shows that you've just read the book 'The Fabric of Reality' and then become expert in Quantum Mechanics.

The double-slit is explained by the Copenhagen Interpretation. I have actually done the double-slit experiment when I was at university, so that is why I asked you in my previous post to explain it. If you can't explain it , then your whole reliance on the book, 'The Fabric of Reality' as your bible, must be dismissed as fantasy.

11/27/2006 11:41:00 pm  
Anonymous Falafulu Fisi said...

Brian said...
[We can infer it from a purely non-mathematical, physical argument, as David Deutsch does in Chapters 2 and 9 of his book The Fabric of Reality when he considers various single-photon interference experiments (see also this video).]

What makes MWI inference any more sense, than say, someone claims that it is GOD who influences the the single-photon outcome? This single-photon interference is again explained by the Copenhagen Interpretation.

Again Brian, you haven't seen a real beam-splitter have you?

David's explanation, that after the photon is split, half will go to other universes and the remaining stays in our universe. How do you know that half of the photon is going to other universes WITHOUT observing them? This formalism has been covered by CI.

You can find the type of apparatus that David described in his video at the Advanced Photonics lab of the Physics Department , Auckland University at the 7th floor. So, this sort of arrangement of mirrors, beam-splitters, optical-delays (delaying the pulse by a small amount of time), tunable lasers (varying photon intensity), optical-rotators (rotating the photon-pulse's polarisation), optical amplifiers (laser amplifier), wavelength multiplexers (combination of different photon-pulses into one pulse). If you want to see this lab, then you can go to see a nice German chap called Professor Rainer Leonhardt, who can organised his post-doc students to show you around.

"Assoc. Professor Rainer Leonhardt"
http://www.phy.auckland.ac.nz/html/r_leonhardt.html

Did you think that David's apparatus, is a new setup to test the MWI? NO, that setup is OLD, where any fibre-optic telecommunication systems of today, does contain a similar setup. This is how a device called wavelength-division multiplexing (WDM) in optical communication systems work. All the signals (from different channels) and combined into one photon pulse, which then travel from source to destination. At the destination, a diffraction grating (multi-slits) is used to split the single pulse into difference channels so these are now separated to be routed into different end-points.

"wavelength-division multiplexing"
http://en.wikipedia.org/wiki/Wavelength_division_multiplexing

So, David's video is not a proof of multiple universes. Actually, he explained of how MWI fits in with the known apparatus he described.

11/28/2006 12:26:00 am  
Blogger Brian S said...

FF -

I answered your question re. the Big-Bang via an analogy with General Relativity. In GR, space-time does not evolve, it simple exists. As does the multiverse.

11/28/2006 12:44:00 am  
Anonymous Falafulu Fisi said...

Brian S said...
[Furthermore, the Many World Interpretation can be used to derive the Born probability rule of Quantum Mechanics.]

Yes, but MWI had still to explain or derive thousands other Quantum Mechanics theoretical framework. Nice effort that it can derive Born Probability, but how about 'Quantum Squeezed States' ? Can MWI explain this ?

"Squeezed Coherent State"
http://en.wikipedia.org/wiki/Squeezed_coherent_state

"Quantum Squeeze Operator"
http://en.wikipedia.org/wiki/Squeeze_operator

There has been real-world application of 'Quantum Squeeze' in fibre-optic telecommunication systems of today.

So, explain 'Squeeze' using MWI?

11/28/2006 12:45:00 am  
Blogger Brian S said...

Eric, the difference between splitting and differentiating is not "just differentiating hairs"!
This is the differentiation model:

. ... .
. ... .
. ... .
| ... |
A --- X
| ....|
A --- X
|
A --- Y
| ... |
A --- Y
| ... |
A --- Y
| ... |
. ... .
. ... .
. ... .


In the differentiation model, the number of universes is constant (infinite) and universes are not created or destroyed. Universes exist eternally, just like moments in General Relativity - see my comment in reply to FF.

The | in the second diagram indicates that universes are fungible (interchangable). Although we can't , for example, distinguish between the 'A's we can define a notion of thickness, or measure. This can't be done in the first diagram. (FF: fungible universes are like the atoms in a Bose-Einstein Condensate: we can't distinguish the atoms but there is such a thing as how many atoms are in the condensate).

Measure is a very important concept. It governs the proportion of universes in which things turn out one way as opposed to another way. And this is where the connection with free will comes in RebelCircumference. For human beings are one of the greatest forces in the multiverse for making sure things do not turn out equally. So although X and Y are real alternatives and although we do choose X AND Y, we do not do so equally.

11/28/2006 12:59:00 am  
Blogger Brian S said...

"This can't be done in the first diagram"

Whoops - I meant this can't be done in the splitting model.

11/28/2006 01:02:00 am  
Anonymous Falafulu Fisi said...

Brian S said...
[In GR, space-time does not evolve, it simple exists.]

Now, we're stuck in language mis-interpretation again. Could you clarify your understanding of the term evolve?

11/28/2006 01:02:00 am  
Anonymous Falafulu Fisi said...

Falafulu Fisi said...
[Could you clarify, your meaning of 'identical' here? I mean that the Copenhagen Interpretation (CI) of Quantum Mechanics, does explain & have demonstrated by experiment of 'Teleportation' phenomena.]

The first Teleportation was experimentally observed about 3 years ago. Again, this was predicted using the Copenhagen Interpretation.

"Experimental Nonlocality Proof of Quantum Teleportation and Entanglement Swapping"
http://www.quantum.univie.ac.at/publications/pdffiles/2002-06.pdf

Prof. Anton Zeilinger is a co-author of the above paper, and he was involved in the Innsbruck team that experimentally confirmed the 'Non-Local Universe'.

Brian, can you explain 'Quantum Teleportation' from an MWI perspective ?

An off-topic, but applicable. Do you think that Nicky Hagger & Ian Wishart are entangle entities, teleported entities, or completely they are entities from other parallel universes , which they have landed in our universe and caused havoc?

11/28/2006 01:21:00 am  
Anonymous Falafulu Fisi said...

Here is the best animation of the Double-Slit experiment, I've seen on the internet.

"Double-Slit by Copenhagen Interpretation"
http://video.google.com/videoplay?docid=-4237751840526284618&q=quantum

11/28/2006 01:47:00 am  
Blogger Brian S said...

FF,

Does this make it clearer?:

General Relavity:
The loaf of bread that is space-time never changes. It was not created and it will never be destroyed. It just is. The loaf can be sliced many ways into moments (depending on a choice of reference frame). The Big-Bang is a part of the space-time continuum. We understand it through moments. But to say that moments were created by the Big-Bang is to imply an external time outside the universe. There is none.

Many Worlds:
The rather-more-complicated loaf of bread that is the multiverse never changes. It was not created and it will never be destroyed. The loaf can be sliced many ways into universes (depending on a choice of basis). The big-bang is a part of the multiverse. We understand it as a point at which all universes were fungible. But to say universes were created by the Big-Bang is to imply some external basis outside the multiverse. There is none.

I recall that PC had an excellent post on the issue of existence. Things just exist. There is no such thing as nothing. That is the case with moments and the multiverse.

11/28/2006 05:47:00 am  
Blogger Berend de Boer said...

rebel radius, indeed. Read Greg Egan on how to prevent taking every path. His invention of the qusp is a brilliant idea.

brian, in former days we had experiments that guided theory. Or we had theory that gave us clear experiments that could distinguish between theories.

If I started to take anything for which some case can be made seriously without any experimental validation I'll be changing my scientific theories more often than my clothes.

11/28/2006 07:29:00 am  
Blogger Brian S said...

Berend -

Let me quote David Deutsch:

"The point that theorists tend to miss is that the multiplicity of reality is not only, or even primarily, a consequence of quantum theory. It is quite simply an observed fact. Any interference experiment (such as the two-slit experiment), when performed with individual particles one at a time, has no known interpretation in which the particle we see is the only physical entity passing through the apparatus. We know that the invisible entities passing through obey the same phenomenological equations of motion (e.g. geometrical optics) as the single particle we do see. And we know from Einstein-Podolski-Rosen-type experiments, such as that of Aspect, that these not-directly-perceptible particles are arranged in extended ‘layers’ each of which behaves internally like an approximately classical universe. Admittedly all these observations detect other universes only indirectly. But then, we can detect pterodactyls and quarks only indirectly too. The evidence that other universes exist is at least as strong as the evidence for pterodactyls or quarks."

I can put it no better than that.

......

Have you read Greg Egan's "Permutation City"?

11/28/2006 08:32:00 am  
Anonymous Falafulu Fisi said...

Brian, here is an email response regarding MWI from Dr. Scott Parkins from the 'Quantum Optics & Quantum Computing' group at Auckland University , Physics , Department.

-------- Scott's Message ----------

Nice to hear from you. The MWI has been put forward by some quite respected physicists and, I believe, appeals to quite a number of other physicists because it provides a way around some long-standing issues associated with measurements on quantum systems. In particular, the basic equation of quantum mechanics, the Schroedinger equation, describes a continuous ("smooth") evolution of the state of a system into a superposition (or sum) of many possible states, each existing at the same time in some sense. However, measurements on quantum systems appear to cause an instantaneous and generally unpredictable "jump" to a single state of the system, which seems inconsistent with a smooth and continuous evolution.

The MWI gets around this "jump" by saying that all possible states in the superposition continue to exist, but in different universes, and we only "see" one universe.

Now, this theory is not inconsistent with what we observe, but it's also not really possible to test this theory, which is why many physicists (including myself) are sceptical, or simply don't think that seriously about it. I believe there are more practical and conventional ways of thinking about the issue of measurement.

In particular, there is a whole field of research associated with quantum measurement theory, which essentially starts from the Schroedinger equation and models the interaction of quantum systems with measurement devices. It is largely able to describe the effects of measurements in a consistent way and show how it is that the measured system "jumps" into a particular state.

Hope that's of some use or interest to you.

Regards,
Scott.

http://www.phy.auckland.ac.nz/html/s_parkins.html

-------- End Scott's Message ----------


Now, I've said to you many times that MWI is physically UNTESTABLE, and that is exactly what Scott's email message stated above. The only other theory in human history that is is UNTESTABLE is the existence of imaginary entities, such as GOD, dead people's spirits, etc, etc,... If something is physically UNTESTABLE as GOD, MWI, etc, etc, then it must be dismissed outright.

You can send a message to Scott if you're still in doubt.

You stated in your article that the opponent's of MWI are not upto date on the latest. I say that it is you who is not upto date on Quantum Physics research, which is obvious from Scott's message that "quantum measurement theory" has been advanced in recent times which try to solve the paradoxes. BTW, it is obvious that Scott is a skeptic and opponent of MWI and he is so upto date on all publications relating Quantum Optics & Quantum Computing. Some of his publications are listed on his website.

11/28/2006 04:37:00 pm  
Blogger Brian S said...

FF,

Thanks for posting the email from Scott. Here is my response:

Nice to hear from you. The MWI has been put forward by some quite respected physicists and, I believe, appeals to quite a number of other physicists because it provides a way around some long-standing issues associated with measurements on quantum systems.

Yes, and one of the papers I linked to in my original post entitled "100 Years of the Quantum" indicates that John Wheeler has finally come around and is now a Many Worlder.

In particular, the basic equation of quantum mechanics, the Schroedinger equation, describes a continuous ("smooth") evolution of the state of a system into a superposition (or sum) of many possible states, each existing at the same time in some sense. However, measurements on quantum systems appear to cause an instantaneous and generally unpredictable "jump" to a single state of the system, which seems inconsistent with a smooth and continuous evolution.

The MWI gets around this "jump" by saying that all possible states in the superposition continue to exist, but in different universes, and we only "see" one universe.

"Gets around this" makes the MWI sound like a dodge, when in fact it is an explantion.

Now, this theory is not inconsistent with what we observe,

And is in fact consistent with everything we observe.

but it's also not really possible to test this theory, which is why many physicists (including myself) are sceptical, or simply don't think that seriously about it. I believe there are more practical and conventional ways of thinking about the issue of measurement.

In particular, there is a whole field of research associated with quantum measurement theory, which essentially starts from the Schroedinger equation and models the interaction of quantum systems with measurement devices. It is largely able to describe the effects of measurements in a consistent way and show how it is that the measured system "jumps" into a particular state.


Note that Scott has put quotes around the word "jump". This is because in quantum measurement theory the jump is instantaneous and unpredictable. The jump is furthermore undetectable: we never catch a system in the process of jumping. The quotes are around the word "jump" because Scott knows that the jump is not the type of physical jump we are all familiar with, which is not instantaneous, not unpredictable, and not undetectable. Scott's "jump" is instantaneous, unpredictable, and undetectable. Therefore Scott cannot in fact directly test this jump and must infer it indirectly, and this is, in principle, no different to the type of reasoning that Many Worlders use. The criticism that the MWI is untestable is therefore one that he cannot consistently maintain.

Scott's explanation is inferior to the MWI for a number of reasons, including the following:

1. It assumes that causality is instantaneous, even across light minutes. This violates relativity, not only the light-speed constraint, but also that there is no relativity of simultaneity: the jump is instantaneous across in *all* reference frames.

2. It cannot explain the apparent randomness of the jump

3. It cannot explain what sort of reality a system has before measurement. Does he maintain that objects are actually in many states prior to measurement, or does he maintain that these states are just possibilities, one of which is actualized on measurement? Or are we just not supposed to ask the question? When the unseen entities passing through the apparatus in a single-photon interference experiment are found to have all the properties of a photon (see Deutsch quote in my previous comment), what are we to regard these as, if not photons?

Scott mentions that he doesn't think seriously about the MWI. I mentioned in my post that it was Deutsch's interest in the MWI that led him to discover universal quantum computers. If he had followed the counsel of pragmatists, then this discovery may never have happened.

11/29/2006 01:11:00 am  
Blogger Brian S said...

FF,

Thanks for posting the email from Scott. Here is my response:

Nice to hear from you. The MWI has been put forward by some quite respected physicists and, I believe, appeals to quite a number of other physicists because it provides a way around some long-standing issues associated with measurements on quantum systems.

Yes, and one of the papers I linked to in my original post entitled "100 Years of the Quantum" indicates that John Wheeler has finally come around and is now a Many Worlder.

In particular, the basic equation of quantum mechanics, the Schroedinger equation, describes a continuous ("smooth") evolution of the state of a system into a superposition (or sum) of many possible states, each existing at the same time in some sense. However, measurements on quantum systems appear to cause an instantaneous and generally unpredictable "jump" to a single state of the system, which seems inconsistent with a smooth and continuous evolution.

The MWI gets around this "jump" by saying that all possible states in the superposition continue to exist, but in different universes, and we only "see" one universe.

"Gets around this" makes the MWI sound like a dodge, when in fact it is an explantion.

Now, this theory is not inconsistent with what we observe,

And is in fact consistent with everything we observe.

but it's also not really possible to test this theory, which is why many physicists (including myself) are sceptical, or simply don't think that seriously about it. I believe there are more practical and conventional ways of thinking about the issue of measurement.

In particular, there is a whole field of research associated with quantum measurement theory, which essentially starts from the Schroedinger equation and models the interaction of quantum systems with measurement devices. It is largely able to describe the effects of measurements in a consistent way and show how it is that the measured system "jumps" into a particular state.


Note that Scott has put quotes around the word "jump". This is because the hypothesized jump is instantaneous and unpredictable. The jump is furthermore undetectable: we never catch a system in the process of jumping. The quotes are around the word "jump" because Scott knows that the jump is not the type of physical jump we are all familiar with, which is not instantaneous, not unpredictable, and not undetectable. Scott's "jump" is instantaneous, unpredictable, and undetectable. Therefore Scott cannot in fact directly test this jump and must infer it indirectly, and this is, in principle, no different to the type of reasoning that Many Worlders use. The criticism that the MWI is untestable is therefore one that he cannot consistently maintain.

Scott's explanation is inferior to the MWI for a number of reasons, including the following:

1. It assumes that causality is instantaneous, even across light minutes. This violates relativity, not only the light-speed constraint, but also that there is no relativity of simultaneity: the jump is instantaneous in *all* reference frames.

2. It cannot explain the apparent randomness of the jump

3. It cannot explain what sort of reality a system has before measurement. Does he maintain that objects are actually in many states prior to measurement, or does he maintain that these states are just possibilities, one of which is actualized on measurement? Or are we just not supposed to ask the question? When the unseen entities passing through the apparatus in a single-photon interference experiment are found to have all the properties of a photon (see Deutsch quote in my previous comment), what are we to regard these as, if not photons?

Scott mentions that he doesn't think seriously about the MWI. I mentioned in my post that it was Deutsch's interest in the MWI that led him to discover universal quantum computers. If he had followed the counsel of pragmatists, then this discovery may never have happened.

11/29/2006 01:14:00 am  
Blogger Berend de Boer said...

brian s, yes I've read most of Greg Egan's work. He has some good material on his website as well.

And brian s, I also don't believe in quarks, so referring to that doesn't help :-)

I'm a realist when it comes to scientific theories and particles and while I find the multiple worlds theory entertaining, it doesn't rise above speculation.

On the slit experiment: there are perfectly valid other explanations. It's sad for the untold worlds which Occam's razor has to eliminate here, let's hope all those otherworldlings don't mind :-)

11/29/2006 12:03:00 pm  
Anonymous Falafulu Fisi said...

Brian S said...
[Yes, and one of the papers I linked to in my original post entitled "100 Years of the Quantum" indicates that John Wheeler has finally come around and is now a Many Worlder.]

Where in that document that stated John Wheeler is now a Many Worlder? That document is about the development of Quantum Mechanics during last century and not about endorsing MWI. In that document it mentioned Prof. Anton Zeilinger who did lead the team to conduct the experiment for the confirmation of the 'non-local universe' plus the confirmation of the 'quantum teleportation phenomena'. If the document was about MWI, it wouldn't have mentioned Prof. Anton Zeilinger's name since all his work were done in the Copenhagen Interpretation framework. The document however did mention MWI of how it avoids paradoxes. That is why the document summarizes Quantum Mechanics over the last 100 years, because of its success (Copenhagen Interpretation) in its prediction capability, which has none so far that is found to be wrong to date. It wasn't a summary about MWI, since it has no single prediction plus, if it proposes some in the future, it will be UNTESTABLE.

John Wheeler is long known to be a critique of MWI even though Everret was his student. His opposition to MWI appeared in his paper, "Include the Observer in the Wave Function?".

Now, I have asked you a question (in fact, many questions), and it hasn't been answered. The question is, "Explain Quantum Teleportation of the type of experiment performed by Professor Anton Zeilinger and his team in terms of MWI perspective? ".

11/30/2006 02:08:00 am  
Anonymous Falafulu Fisi said...

Dr. Scott Parkins said...
[Now, this theory is not inconsistent with what we observe]

Brian S reply...
[And is in fact consistent with everything we observe.]

Brian, I have already said this answer to you in the original 'Entropy' thread. Didn't you remember that? Why are you re-stating this again? Are you running out of points to fill in for the debate here? What I stated in that thread is that different formulations and interpretations of Quantum Mechanics could explain most things we observe, however, they are different in predictive power. TEW (Theory of Elementary Waves) does also explain most observations already established by Copenhagen Interpretation (CI). MWI does the same. The difference is that MWI & TEW have not proposed any predictions yet? Also most of the established CI derivations are not yet accounted for or explained in terms of MWI or TEW perpective. For example, was the derivation of "Quantum Squeezed States" (QSS) , in which I have asked you in a previous post to provide an explanation in terms of MWI perpective, and you haven't been able to provide one so far. You can ask Dr. Scott Parkins which is one of his research domain of interest to explain to you what it is and its technological application, which has been available for commercial use over recently times . In fact the Quantum Optic/Computing group at Auckland Physics Department, where Scott is a member, is a leader in QSS research, which they followed on from the pioneering work of late Prof. Daniel Walls, who proposed this phenomena in the 1980s. You can visit the Photonics lab at Auckland to see these fantastic state-of-the-art devices invented via the theoretical framework of the Copenhagen Interpretation.

Here is an article on the application of 'Quantum Squeezed State' soliton photon pulse, for high speed fibre-optic telecommunication network.

"Quantum solitons"
http://physicsweb.org/articles/world/12/2/8/1

In the Photonics lab, there are lasers and fibre-optic for soliton transmission, if you're curious about these gadgets as a result of the Copenhagen Interpretation, just contact Scott or anyone from his group to go there and witness the predictive power of CI.

11/30/2006 02:41:00 am  
Anonymous Falafulu Fisi said...

Brian,

Another question that I am still waiting for an explanation from you, but none so far, is for you to explain how the double-slit experiment is accounted for by MWI?

It would be nice if you answer some unanswered questions I have put forward to you in my previous posts, so that we can move forward in the debate. It looks like to me that you're evading. If you provide answers to outstanding questions, then I will then, able to come up with more questions to ask. It is hard to ask you more questions if the previous questions are still left unanswered.

11/30/2006 03:01:00 am  
Anonymous Falafulu Fisi said...

Brian S said...
[It assumes that causality is instantaneous, even across light minutes.]

You used the word 'assume', but ISN'T MWI does 'assume' there exist other universes?

Now, I've pointed you out to the Innsbruck double-delay-choice experiment which confirm non-local interaction of correlated particles. I have pointed out Prof. Prof. Anton Zeilinger's paper on 'Non-local Universe', which is the double-delay experiment.

11/30/2006 03:09:00 am  
Anonymous Falafulu Fisi said...

Brian S said...
[This violates relativity, not only the light-speed constraint, but also that there is no relativity of simultaneity: the jump is instantaneous in *all* reference frames.]

Now, perhaps this is the third time I've asked you this question, and I hope that answer this time.

How, does the Copenhagen Interpretation violate relativity? What condition(s) in relativity theory that is being violated?

11/30/2006 03:13:00 am  
Blogger Brian S said...

FF,

I am not being evasive when I don't answer all of your questions: I simply don't have the time!

And given that I am short of time right now, I'll refer to you Alan Forrester's MWI explanation of teleportation on The Fabric of Reality list (this list has thousands of posts on the MWI and is an excellent resource). See also the Deutsch and Hayden paper which I have referred you to previously and for which the abstract follows:

All information in quantum systems is, notwithstanding Bell's theorem, localised. Measuring or otherwise interacting with a quantum system S has no effect on distant systems from which S is dynamically isolated, even if they are entangled with S. Using the Heisenberg picture to analyse quantum information processing makes this locality explicit, and reveals that under some circumstances (in particular, in Einstein-Podolski-Rosen experiments and in quantum teleportation) quantum information is transmitted through 'classical' (i.e. decoherent) information channels.

And if you pay attention to this paper it clearly explains why experiments like Zeilinger's are not demonstrations of non-locality. Non-locality is a non-explanation concocted by those determined to hold onto single-universe physics.

A star 10 light years away emits a photon. In the CI it spreads out as a kind of probability wave so that by the time it reachs Earth the wave is spread across a sphere 10 light years in diameter. When a human eye detects the photon, the wave instantaneously collapses across all those light years. So you have a spherical region of space 20 light years across that somehow "knows" straight away that the photon hit an eye. And even when we consider an observer moving relative to the eye, that observer does not notice any relativity of simultaneity of the collapse (the collapse is still simultaneous with the photon hitting the eye). What nonsense!

I don't believe in arguments by authority so it is neither here nor there what John Wheeler believes, but the Tegmark & Wheeler paper is mostly a discussion of the MWI and it is pretty clear that both authors are Many Worlders (and Max Tegmarks website has more multiverses than you can poke a stick at!). They conclude their main discussion with this:

"...we constantly keep entering into superpositions of different mental states, but decoherence prevents us from noticing this - subjectively we (all superposed versions of us) just perceive this as the slight randomness that disturbed Einstein so much"

How much more MWI can you get? This paper is a fairly recent paper so it is a pretty good indication of Wheeler's current position (though it is always hard to tell with him because he changes his mind so much!)

11/30/2006 09:56:00 am  
Blogger Brian S said...

"10 light years in diameter"

um, radius.

11/30/2006 10:00:00 am  
Blogger The Hand of Morthos said...

I presume you created a Strawman there, Brian, in order to save time, but the following is nonsense:

'A star 10 light years away emits a photon. In the CI it spreads out as a kind of probability wave so that by the time it reachs Earth the wave is spread across a sphere 10 light years in diameter. When a human eye detects the photon, the wave instantaneously collapses across all those light years. So you have a spherical region of space 20 light years across that somehow "knows" straight away that the photon hit an eye. And even when we consider an observer moving relative to the eye, that observer does not notice any relativity of simultaneity of the collapse (the collapse is still simultaneous with the photon hitting the eye).'

There is no knowing here; it is just the way observation works in regard to indeterministic systems.

Also, for someone who disdains appeals to authority you really should get off your high horse about Deutsch.

11/30/2006 06:36:00 pm  
Anonymous Falafulu Fisi said...

Brian S said...
[See also the Deutsch and Hayden paper which I have referred you to previously and for which the abstract follows:]

I have to ask if you , yourself paid any attention to that paper at all? Can I ask you to stop quoting papers for the sake of quoting them, because obviously, you don't pay attention to them.

Did you notice the date of publication of the paper? Here is a clue for you, go over the link I have shown you in this thread and find the link for the Innsbruck double-delay choice paper and compare the 2 papers date of publications. You will be surprised to find out that David Deutsch's paper went to publication at around the same time as the Innsbruck paper. What does that mean? It means that Deutsch, had not had a chance to inspect the Innsbruck paper, which might force him to change the content of his paper. Why would he have done that? Because , on the face of experimental evidence, you just do not simply look away and ignore facts. This happens most of the time in science.

Here is an example of a Physicist (David Harriman) who was a strong proponent of TEW (Theory of Elementary Waves) interpretation of Quantum Mechanics until he became aware of the 'Innsbruck Double-delay Choice' experiment in the late 1990s. The Innsbruck experiment established once and for all that non-local interaction (a.k.a Non-Local Universe) DOES indeed exist. David Harriman did abandon his support for TEW, simply because he couldn't ignore scientific facts. TEW & MWI are both local theories.

You can read about his withdrawal of supporting TEW here:

"Statement on the Theory of Elementary Waves"
http://www.objectivescience.com/articles/dh_tew.htm

Brian, I am sick of repeating myself to you and I hope that I don't have to explain this to you again, because I had already mentioned this very clearly in the 'Entropy' thread, about the almost simultaneous publication of Deutsch's paper & the Innsbruck's paper. That is Deutsch was not even aware of the experimental facts, where his paper was trying to debunk Bell's Theorem as myth. After all, the confirmation of non-locality where Bell's Theorem was violated by the Innsbruck team is no myth, but facts. Indeed, MWI is the myth, because it is UNTESTABLE.

11/30/2006 11:11:00 pm  
Anonymous Falafulu Fisi said...

Brian S said...
[Non-locality is a non-explanation concocted by those determined to hold onto single-universe physics.]

No, those who are determined to hold on to single-universe physics are from the majority of the Physics research community and have formed well-established foundations of understanding in theoretical physics. MWI is a minority group which had none whatsoever proposed any PREDICTIONS yet. It has not made any contribution to real world technologies yet after 50 years when it was first proposed. Its only hope is Quantum computers, but CI (Quantum Mechanics) is on a fast track to built the first quantum computer, which would likely to beat the MWI proponents. This is true where proto-types had been built at US government Nuclear facility, Los Alamos in the late 1990s and early 2000s.

Here are some questions that you might want to answer.

#1) How, do the many universes interact?

#2) If they do interact, then how often?

#3) How many universes can interact simultaneously?

#4) What makes those universes parallel?

#5) Do the objects from our universe disappear to the other universes?

#6) Do those universes occupy the same space?

Brian, can you give answers to those questions above?

11/30/2006 11:30:00 pm  
Anonymous Falafulu Fisi said...

Brian S said...
[How much more MWI can you get? This paper is a fairly recent paper so it is a pretty good indication of Wheeler's current position (though it is always hard to tell with him because he changes his mind so much!)]

That John Wheeler & Max Tegmarks paper is an essay and not a peer review one. It was written for the Scientific American magazine.

You know and I know, that peer review papers have more weight than essays or articles written for the general public print media such as Scientific American or newspapers. So, the Wheeler & Tegmarks paper has no weight (in fact zero), at all in its content, to make Many Worlder be in the same par as the Copenhagen Interpretation of Quantum Mechanics.

11/30/2006 11:51:00 pm  
Anonymous Falafulu Fisi said...

Brian, here is a quote from Alan Forrester's page:

Alan Forrester said...
[If you measure a sharp observable then you get the same result across all universes (barring faults in the measuring device). What happens if you measure an unsharp observable? Well, before the measurement there is only one version of the measuring device, afterward there are two versions in parallel universes, each one of which records one of the possible measurement results.]

Does a specific universe split into 2 or more as quoted by Alan in his message above? If it does indeed split into 2 everytime a measurement is made, then this is a direct contradiction to a previous post where you said, that universes don't split but they differentiate?

Which is the correct answer Brian? Is it SPLITTING or DIFFERENTIATION? Or perhaps that you, yourself are also lost in the language interpretation of MWI?

12/01/2006 12:32:00 am  
Blogger Brian S said...

FF,

Did you split into multiple versions, each of which is posting here?

I don't know why you keep saying Zeilinger's results refutes the Deutsch and Hayden paper. It doesn't. Just the opposite. It is confirmation of the MWI view, as Frank Tipler explains here:

Abstract:
Quantum nonlocality may be an artifact of the assumption that observers obey the laws of classical mechanics, while observed systems obey quantum mechanics. I show that, at least in the case of Bell's Theorem, locality is restored if observed and observer are both assumed to obey quantum mechanics, as in the Many-Worlds Interpretation. Using the MWI, I shall show that the apparently "non-local" expectation value for the product of the spins of two widely separated particles --- the "quantum" part of Bell's Theorem --- is really due to a series of three purely local measurements. Thus, experiments confirming "nonlocality" are actually confirming the MWI.

Anyway, I'm feeling more and more like one of the gun-slingers in PC's cartoon, so I'm going to leave the discussion for now.

Your six questions are good questions and I suggest you post them to the Fabric of Reality list where I'm sure you will receive some very reasonable answers.

12/01/2006 09:28:00 am  
Anonymous Mark Sadgrove said...

I probably shouldn't wade in here, but it is nice to see this topic being discussed on a New Zealand oriented site, simply because, academically speaking, there are some fine minds in this country when it comes to research into fundamental quantum physics, and it would be nice if that translated into wider public interest.

Disclaimer: I'm a Quantum Physics PhD who has published work with Rainer Leonhardt and Scott Parkins mentioned in comments above. Specifically, my own work could be said to err more towards supporting the notion that interaction with the outisde world is the only thing that's needed to explain the quantum measurement problem away... Having said that, the Many Worlds Interpretation is still an interpretation rather than a theory with new, testable predictions as far as I'm aware so I'm really no more qualified than anyone else or for that matter any more biased by my use of established quantum theory when it comes to commenting on this stuff.

I have a few points to make:

1) The "Many worlds interpretation" is still called an interpretation. Is anyone aware of any specific predicitions that Many Worlds theory makes which are outside of standard quantum theory? In this case there might be hope for confirming it one way or another...

I seem to recall that some (perhaps prominent?) physicists have said that a successful quantum computer would force people to believe the many worlds theory because, well, that super-classical computing power must be coming from somewhere , the idea being that we share the possible computing power of a huge number of somehow existent universes when we use a quantum computer. Personally I still don't find this convincing. From a very utilitarian point of view, that computing power arises because nature, as embodied in the laws of quantum mechanics, allows it to occur. quantum mechanics just works that way and that's that. The reason people are groping for interpretations is because they find it difficult to form a clear, intuitive picture of the natural process that is occuring, unlike in classical mechanics where little balls colliding with each other is to a crude degree all the mental imagery you'll ever need ;). But an interpretation is just window dressing until it actually leads to intuition which makes NEW predicitions. Smarter people than me are backing many worlds, but I'd like to know if they've made any progress on the prediciton front.

2) I always thought that the most compelling reason for being suspicious of MWI was Occam's razor which states that given the infinite possible explanations that one can give for a physical phenomenon, the simplest possible explanation (that is the one with the fewest parameters) should be preferred. Many worlds multiplies Universes ad infinitum just so we can have a cosy mental picture of the natural processes described by QM. A lot of people think that this is a dear price to pay! This is a capitalist oriented site right. So do you really think that Nature would be this wasteful of resources when cleaner, more efficient single universe models can explain things just as well? ;););) (Of course, the point is that some people think that ONLY MWI can explain all the observed phenomena in which case it doesn't matter how "wasteful" it seems, because it's the only game in town.)

Another way to look at it is through the testability lens which a lot of people have also brought up. If you claim that there are multitudinous other universes which are created by quantum "splitting" or "differentiation" events but, oh hang on, you can't ever reach them or even feel their influence except via a rather unspectacular interference experiment, why should I believe you? People who do believe such things are, for example, good candidates for believing that there is a very specific God in Heaven - a bearded man in the Judeo-Christian tradition for example, exactly as described in the bible. While we have no real evidence of such specifics, believers might say, if exactly such a god did exist it explains a few things about the world. Well perhaps, but why believe all these things that you can't verify along with the very general idea of a creator which does not imply any specific form for god.
=>
Do we really have to swallow a multiverse teeming with infinite slightly differentiated universes all equally "real" just to explain the quantum measurement problem? Are there leaner versions of many worlds without infinite versions of each of us floating around in them?

(3) Remember that Physicists don't have to buy into any interpretation of quantum mechanics to use it effectively. In a comment above, Brian S took Scott Parkins' to task about a quantum jump "interpretation". But I don't think Scott was using any interpretation. The jump issue in quantum mechanics, or the collapse of the wavefunction, ra, ra, ra, whatever you wish to call it, is I think the bare minimum theory needed to predict naturally observable events. I don't agree that there is any interpretation going on here. The facts are that when you look at the distribution of photons from a slit experiment on a detector screen, each one makes a "dot" at just one point - that's your measurement. To describe the distriution of points you use quantum mechanics. Quantum mechanics describes the photon as a "delocalised" or non-pointlike entity - a wave as such which gives the requisite interference pattern. It also provides a probabalistic rule telling you how likely a given measurement is given the form of this wave. What you do to connect the wave model of the pre-measurement photon to the measurement you actually make - your interpretation of the observed physical phenomenon - is up to you, but it doesn't change the basic description of what happens which is standard quantum mechanics.

Some rather vocal proponents of the decoherence project think that they've got the quantum measurement problem - jumps and all - ironed out by just considering the interaction of a closed quantum system with it's environment. I favour decoherence myself (remember I'm biased - I invoke it a little in my thesis) because it seems clean. The idea is that the idea is that the nice probability waves that don't have any particular "position" are in reality rapidly converted into particular "classical" states in any real system because there is interaction with the environment. I don't think many people believe that decoherence theory is enough to explain the measurement problem away completely, but it IS a theory and it does help make sense of certain experimental observations to some degree. Personally, decoherence looks to me like Quantum Mechanics without the difficult jump, but with the Born Rule explained (see W. H. Zurek, Probabilities from envariancerd, eprint quant-ph/0405161 (2004) - still controversial!!!) and no multiple Universes required. Reading the recent Wheeler preprint ("100 Years of the quantum") referenced in a comment above (Brian S again?) the Decoherence theory is in fact presented as being an important addition to Everett's many worlds theory and not an explanation in competition with it. I am not convinced after a cursory review of that paper that there is really anything left to explain if decoherence works as well as Tegmark and Wheeler imply in this preprint, but even so the "Many Worlds" they describe does not seem as grandiose as the usual idea of infinite simultaneously exisiting Universes being almost identical to our own. Rather, a far more subtle "Many Minds" idea is suggested which seems rather different to me, or at least is far less suggestive in a sci fi sense.

Okay sorry to go on an on. Maybe my over all point is that Many Worlds Interpretation seems to excite a lot of people, when it's really a subtle idea and refinement might remove a lot of the sci fi elements of it, if it even survives as an attempt to provide a picture of the undoubtedly successful quantum mechanical laws. It seems to me that the successful implementation of Shor's algorithm alone is not enough to irrefutably prove the existence of multiple "mes" in Universes which I can never otherwise observe the effect of.

As a final note, I attended the Quantum Physics of Nature last year and saw Zeilinger's labs in Vienna. Very nice! I also heard debates about precisely this stuff and I can assure you that the physics community is nowhere near a consensus...

12/01/2006 06:49:00 pm  
Anonymous Falafulu Fisi said...

Brian,

Are you taking Professor. J. Tipler seriously? Prof Tipler who comes out with weird idea such as 'The Anthropic Principles' ?

"The Anthropic Coincidences"
http://www.stephenjaygould.org/ctrl/stenger_intel.html

I suspect that it won't be too long , Professor Tipler would declare that GOD exist? It has been reported in some articles on the internet, that Tipler himself had indicated indirectly in an interview that he is not ruling out the existence of a grandmaster designer. Does this familiar to you? He is stop short of endorsing 'Intelligent Designer'.

Now, the Non-local test conducted by Zeilinger , et al, was based on the well established BELL theoretical framework. Note that there is no such framework in MWI , where its falsification could be tested on. If Bell is violated, then non-locality interaction does indeed exist. That is why it stands up. You can't falsify something by just throwing in arbitrary. As I recalled PC, saying that Ayn Rand stated that if there is no proof, then the arbitrary claim has to be thrown out, no ifs no buts, just out. That is exactly what happens to MWI? It has no framework established that it can be tested on its validity. MWI is UNTESTABLE.

BTW, I fired an email to David Deutsch, asking if MWI had proposed any predictions yet and he said, that it is impossible at present to test. I have also sent 2 emails to Frank Tipler asking to state the predictions proposed by MWI if any. He never replied back.

MWI does come and try to give explanations to Physics formulations that are already known. It was 'Born Probabiliy' , then 'Non-Locality' and so forth, BUT it has not propose anything new so that researchers will hone their target (research subject) into and find out if such physical entity or action does indeed allowable in nature. So, MWI is more like when someone has eaten his meal (dinner, etc), and the left-overs would be cleaned up by the beggars. Beggars don't produce anything original, they only come afterwards, to clean up the leftovers put aside to them by the wealthy producers.

12/01/2006 06:57:00 pm  
Anonymous Falafulu Fisi said...

Mark Sadgrove said...
[I'm a Quantum Physics PhD who has published work with Rainer Leonhardt and Scott Parkins mentioned in comments above.]

Mark , Welcome. Perhaps, that your long comment be re-posted by PC (owner of the blog) as Part 2. I suspect that PC, will come out with an article of his own, in terms of philosophical implications of Quantum Mechanics, perhaps part 2, if your very nice post is not to be made as part 2, then PC can post his one as part 3.

I was at the Department as well in the mid-1990s, and late Professor Dan Walls & Prof. Mathew Collete were the lecturers for Quantum Mechanics. Prof. Leonhardt & Prof. Harvey were the ones teaching 'Opto-Electronics'. Dr. Bold's son (Geoff) was in the same class as me.

I guess that I will see you at the 'inaugural symposium of the Dodd-Walls Centre for Photonics and Ultra Cold Atoms' , next Saturday week , that is 9 December.

I might try & spot you for a chat.

12/01/2006 07:15:00 pm  
Blogger Brian S said...

Mark,

Why should I believe you are conscious? After all, the only consciousness I ever experience is my own and I cannot experience your consciousness. Isn't believing in billions of other consciousnesses just to explain the reality of my own perceptions wasteful? Surely nature is much more parsimonious?

FF,

I'm well aware of Frank Tipler's stranger theories, but he would hardly be the first scientist to believe in a creator. I cite him because I think that his point about non-locality is correct. Arguments need to be taken on a case-by-case basis, for a man who is wrong about many things can be right about some things.

BTW - The multiverse considered as a whole is a much much simpler thing than any particular universe and in fact contains zero net information.

12/02/2006 09:06:00 am  
Anonymous Falafulu Fisi said...

Brian,

In one of your post, you've stated that Copenhagen Interpretation violates Relativity Theory.

Now, I think that this is the fourth time I have asked you to explain this violation, and again you have evaded giving an answer .

First, I suspect that the reason you don't want to answer is that you DON'T know. You might have read some books where it mentioned the "superluminal" (faster than speed of light), where you JUMPED and think "AHA" , Copenhagen Interpretation of Quantum Mechanics violates one of the conditions of Theory of Relativity.

I want to state this very important quote to you, and perhaps you then bloody answer my question and stop evading.


"Copenhagen Interpretation of Quantum Mechanics DOES NOT violate any of the Theory of Relativity proposals"

You've have stated before in NotPC that you have a background in Signal Processing. So, I will give you some hints if your Signal Processing lecturer didn't give you enough information on WAVE PROPAGATION.

Look for the followings perhaps by Google:

#1) Signal Group Velocity
#2) Relativity Physical Signal Transformation Rate


Brian, if your former Signal Processing lecturer didn't teach you point #1 , then I urge you put a fill-in a claim form and demand that part of your fees for the course be refunded because he/she didn't teach you the principles of WAVE PROPAGATIONS. This is just Physics 101.

12/02/2006 05:21:00 pm  
Blogger Brian S said...

FF,

I have explained the point several times now. You believe in an instantaneous, undetectable, and unpredictable collapse. That not only violates relativity, it violates common sense. Now I know Copenhagenists claim that because no energy, information, or matter is transfered during the collapse, relativity is not violated (and we can only learn about collapse after the fact by good old classical processes). But think about it: you're basically postulating a magical process to get around explaining anything. You may as well put God in the equation.

12/03/2006 08:44:00 am  
Anonymous Anonymous said...

Do you think, in these other universes that the 'Borg' would have a dominate role in intergalatic affairs?

12/04/2006 12:23:00 pm  
Anonymous Falafulu Fisi said...

Anonymous said...
[Do you think, in these other universes that the 'Borg' would have a dominate role in intergalatic affairs?]

I think that if there is such a thing as Borg in other universes then those Borgs and those universes are only imaginary and not real ones.

12/04/2006 12:51:00 pm  
Anonymous Anonymous said...

What about the 'Clingon Empire' then- their political ideology of world and/or universe domination is well documented.

12/04/2006 01:06:00 pm  
Anonymous Falafulu Fisi said...

Anon said...
[What about the 'Clingon Empire'?]

May be that's the empire that Tom Cruise and the Church of Scientology are members of.

12/04/2006 01:40:00 pm  
Anonymous Anonymous said...

Everyone knows- the Church of Scientology do not accept the 'Many Worlds, Interpretation' per se, but take a more broader view to the 'Chewbecca' theory of relativity.

12/04/2006 02:10:00 pm  
Anonymous Mark Sadgrove said...

Anyone still reading this thread? I just noticed a brief chat with David Deutsch posted on the New Scientist site (the Woman's Weekly of science publications eh?) The link is:
here

Deutsch is obviously a REALLY smart guy and I find his arguments stimulating and his criticism of the utilitarian approach to physics rather trenchant (I guess I effectively promoted this approach in my first post). But damned if I still don't feel CONVINCED by his argument about the power of quantum computers proving many worlds. I won't feel convinced ever, in fact, unless someone can provide me MATERIAL proof (or similar) of those worlds. The existence of some large calculating resource outside of our universe is very different (to me at least) to the idea of multiple universes populated with multiple you-and-is. I feel compelled to be cynical about such an idea from the core of my scientific cynicism... but then why doesn't a smart guy like David Deutsch I wonder?

Brian S, as for your comment about the consciousness of others, well perhaps we can agree that, apart from all the emotional stuff that makes me regard others as conscious like myself, from a rational viewpoint, the consciousness of others will always remain a (very useful) hypothesis which we will never be able to verify directly. I don't really think that's solipsism just a brutal fact. But to boil down your argument to it's point, perhaps it's more illuminating to ask why nature bothers to be anything at all... I mean apart from doubting the existence of others, I should perhaps doubt the existence of my physical body (clearly unecessary and wasteful merely to create the perception of a physical body which I experience) etc etc, and in fact even the existence of a coherent, enduring "I" seems doubtable. But I think that you interpret my Occam's Razor argument as a solipsist sort of argument. My point was that given what we observe in nature, the Many Worlds Interpretation seems to require a lot more resources to explain the observations than interpretations such as Copenhagen or (pushing it) Decoherence. Now maybe I'm just a utilitarian without the mental muscle/intellectual courage to require that Science explain the world as Deutsch requires. Certainly, Deutch's requirement that physics be about the real world rather than just a set of equations used for prediction resonates with me, as you'd hope it resonates with any inquisitive person. Nonetheless, I think that in the end, one must balance scepticism against the will to explain. And furthermore, there are many different levels of explanation. A completely utilitarian scientist (that is one who does not believe that science is describing the world as it really is but rather believes that science is a just set of tools to make predictions about the world which is refined according to the scientific method of hypothesis testing) will still start to inhabit the theories they work with and gain an intuition about a theory's workings, form mental pictures of the theory and, yes, start to ascribe the status of a description of reality to this theory. I don't think you can be a pure utilitarian as a scientist - the will to explain naturally leads you to connect your equation with reality. And this is an important part of the scientific process - something that one can't imagine today's computers doing for example, even though they could in principle carry out hypothesis testing which is the basis of science.

Again, I'm being long winded, but my point is that most scientist's in my opinion are neither complete logical positivists of David Deutsch's ilk or utter utilitarians.

Briefly, a spontaneous collapse is not described by quantum mechanics. There is just a rule giving probablities for a certain result. It's true that until you apply this rule you use Schrodinger's equation to evolve the system deterministically, and for practical purposes you take the time at which you stop using the SE and apply the rule to be exactly when you choose to make the measurement. In Decoherence theory, the actual collapse takes a finite (but extremely brief) time. In any case, as others have pointed out, I don't see the relativity busting superluminal flow of information going on here even if the collapse is instantaneous.

Anyway, the discussions here seem really sophisticated and often hard for me to follow. Out of interest how many people here have spent time learning physics or philosphy at Uni? Obviously neither is a requirement for having good insight into this issue. Perhaps an impedement, ha ha! I would love to hear what the real smarties in my old department have to say on this issue though!

Best,
Mark S.

P.S. FF - I live and research in Tokyo now so I couldn't make it to the Dodd Walls symposium. How was it?

12/08/2006 07:22:00 pm  
Anonymous Michael Bacon said...

Because test aren't currently technically feasible, doesn't mean that something can never be tested. GR couldn't be fully tested until relatively recently (and further tests are being dreamed up even now to test it further to smaller scales). The tests that have been put forward with respect to the MWI (http://plato.stanford.edu/entries/qm-manyworlds/#5)aren't currently feasible, but for the most part they only entail progress on the engineering side -- there aren't issues of principle. Time will tell.

2/21/2007 08:40:00 am  
Blogger James Redford said...

For much more on Prof. Frank J. Tipler and God, see Tipler's below paper, which among other things demonstrates that the known laws of physics (i.e., the Second Law of Thermodynamics, general relativity, quantum mechanics, and the Standard Model of particle physics) require that the universe end in the Omega Point (the final cosmological singularity and state of infinite informational capacity identified as being God):

F. J. Tipler, "The structure of the world from pure numbers," Reports on Progress in Physics, Vol. 68, No. 4 (April 2005), pp. 897-964. http://math.tulane.edu/~tipler/theoryofeverything.pdf Also released as "Feynman-Weinberg Quantum Gravity and the Extended Standard Model as a Theory of Everything," arXiv:0704.3276, April 24, 2007. http://arxiv.org/abs/0704.3276

Out of 50 articles, Prof. Tipler's above paper was selected as one of 12 for the "Highlights of 2005" accolade as "the very best articles published in Reports on Progress in Physics in 2005 [Vol. 68]. Articles were selected by the Editorial Board for their outstanding reviews of the field. They all received the highest praise from our international referees and a high number of downloads from the journal Website." (See Richard Palmer, Publisher, "Highlights of 2005," Reports on Progress in Physics. http://www.iop.org/EJ/journal/-page=extra.highlights/0034-4885 ) Reports on Progress in Physics is the leading journal of the Institute of Physics, Britain's main professional body for physicists.

See also the below resources for further information on the Omega Point Theory:

Theophysics http://theophysics.gigacities.net
http://geocities.com/theophysics/

"Omega Point (Tipler)," Wikipedia, April 16, 2008 http://en.wikipedia.org/w/index.php?title=Omega_Point_%28Tipler%29&oldid=206077125

"Frank J. Tipler," Wikipedia, April 16, 2008 http://en.wikipedia.org/w/index.php?title=Frank_J._Tipler&oldid=205920802

Tipler is Professor of Mathematics and Physics (joint appointment) at Tulane University. His Ph.D. is in the field of global general relativity (the same rarefied field that Roger Penrose and Stephen Hawking developed), and he is also an expert in particle physics and computer science. His Omega Point Theory has been published in a number of prestigious peer-reviewed physics and science journals in addition to Reports on Progress in Physics, such as Monthly Notices of the Royal Astronomical Society (one of the world's leading astrophysics journals), Physics Letters B, the International Journal of Theoretical Physics, etc.

Prof. John A. Wheeler (the father of most relativity research in the U.S.) wrote that "Frank Tipler is widely known for important concepts and theorems in general relativity and gravitation physics" on pg. viii in the "Foreword" to The Anthropic Cosmological Principle (1986) by cosmologist Prof. John D. Barrow and Tipler, which was the first book wherein Tipler's Omega Point Theory was described.

The leading quantum physicist in the world, Prof. David Deutsch (inventor of the quantum computer, being the first person to mathematically describe the workings of such a device, and winner of the Institute of Physics' 1998 Paul Dirac Medal and Prize for his work), endorses the physics of the Omega Point Theory in his book The Fabric of Reality (1997). For that, see

David Deutsch, extracts from Chapter 14: "The Ends of the Universe" of The Fabric of Reality: The Science of Parallel Universes--and Its Implications (London: Allen Lane The Penguin Press, 1997), ISBN: 0713990619; with additional comments by Frank J. Tipler. http://theophysics.gigacities.net/deutsch-ends-of-the-universe.html

The only way to avoid the Omega Point cosmology is to invent tenuous physical theories which have no experimental support and which violate the known laws of physics, such as with Prof. Stephen Hawking's paper on the black hole information issue which is dependant on the conjectured string theory-based anti-de Sitter space/conformal field theory correspondence (AdS/CFT correspondence). See S. W. Hawking, "Information loss in black holes," Physical Review D, Vol. 72, No. 8, 084013 (October 2005); also at arXiv:hep-th/0507171, July 18, 2005. http://arxiv.org/abs/hep-th/0507171

That is, Hawking's paper is based upon proposed, unconfirmed physics. It's an impressive testament to the Omega Point Theory's correctness, as Hawking implicitly confirms that the known laws of physics require the universe to collapse in finite time. Hawking realizes that the black hole information issue must be resolved without violating unitarity, yet he's forced to abandon the known laws of physics in order to avoid unitarity violation without the universe collapsing.

Some have suggested that the universe's current acceleration of its expansion obviates the universe collapsing (and therefore obviates the Omega Point). But as Profs. Lawrence M. Krauss and Michael S. Turner point out in "Geometry and Destiny" (General Relativity and Gravitation, Vol. 31, No. 10 [October 1999], pp. 1453-1459; also at arXiv:astro-ph/9904020, April 1, 1999 http://arxiv.org/abs/astro-ph/9904020 ), there is no set of cosmological observations which can tell us whether the universe will expand forever or eventually collapse.

There's a very good reason for that, because that is dependant on the actions of intelligent life. The known laws of physics provide the mechanism for the universe's collapse. As required by the Standard Model, the net baryon number was created in the early universe by baryogenesis via electroweak quantum tunneling. This necessarily forces the Higgs field to be in a vacuum state that is not its absolute vacuum, which is the cause of the positive cosmological constant. But if the baryons in the universe were to be annihilated by the inverse of baryogenesis, again via electroweak quantum tunneling (which is allowed in the Standard Model, as B - L is conserved), then this would force the Higgs field toward its absolute vacuum, cancelling the positive cosmological constant and thereby forcing the universe to collapse. Moreover, this process would provide the ideal form of energy resource and rocket propulsion during the colonization phase of the universe.

Prof. Tipler's above Reports on Progress in Physics paper also demonstrates that the correct quantum gravity theory has existed since 1962, first discovered by Richard Feynman in that year, and independently discovered by Steven Weinberg and Bryce DeWitt, among others. But because these physicists were looking for equations with a finite number of terms (i.e., derivatives no higher than second order), they abandoned this qualitatively unique quantum gravity theory since in order for it to be consistent it requires an arbitrarily higher number of terms. Further, they didn't realize that this proper theory of quantum gravity is consistent only with a certain set of boundary conditions imposed (which includes the initial Big Bang, and the final Omega Point, cosmological singularities). The equations for this theory of quantum gravity are term-by-term finite, but the same mechanism that forces each term in the series to be finite also forces the entire series to be infinite (i.e., infinities that would otherwise occur in spacetime, consequently destabilizing it, are transferred to the cosmological singularities, thereby preventing the universe from immediately collapsing into nonexistence). As Tipler notes in his 2007 book The Physics of Christianity (pp. 49 and 279), "It is a fundamental mathematical fact that this [infinite series] is the best that we can do. ... This is somewhat analogous to Liouville's theorem in complex analysis, which says that all analytic functions other than constants have singularities either a finite distance from the origin of coordinates or at infinity."

When combined with the Standard Model, the result is a Theory of Everything (TOE) correctly describing and unifying all the forces in physics.

4/17/2008 11:34:00 am  

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