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[P]
Qubits in your future

By iGrrrl in Technology
Mon Dec 04, 2000 at 03:21:34 PM EST
Tags: Science (all tags)
Science

I love it when real science is wierder and cooler than science fiction or wrongheaded mystical interpretations of science fact.

In a recent article on Edge, physicist David Deutsch says that a quantum computer, "...would be an object far more complex than the whole of the classical universe. "


David Deutsch became a hero to me when I found out that he has piles of science fiction books in his Oxford home, loves Macintosh computers, and hates Microsoft. If that weren't enough, he takes the 'many universes' idea of quantum mechanics, and strips it of its possible mystical fantasies. (I like this particularly because of the mysticism the non-biologists sometimes attach to the Gaia hypothesis.) Deutsch explains himself well in the interview on Edge, and also in a print article in The American Scholar (Summer, 2000). In the print article, he recounts much of the history of the theory of quantum computing, including his conversation with Charles Bennet of IBM. It took place at the first conference on the physics of computers. I quote from the text.

"So I said, 'I think this complexity theory stuff is a load of rubbins," Deutsch recalls. "And Bennett said 'Oh?' very politely -- he'd done quite a lot of work on it himself -- 'What makes you say that?' And I said, 'There's nothing fundamental in the theory of computation that tells you wha the instruction set is.' Then Charlies says simply, 'The instruction set is physics.' I sort of gasped and took two steps backwards."

...Catching his breath, [Deutsch] snapped back at Bennett, "If the instruction set is physics, then you guys are using the wrong physics."

The rest, as they say, is history -- one in which Deutsch re-worked Turing's famous paper using quantum physics. It took him several years.

Deutsch certainly isn't the only name in quantum computing, and the links below will take you to places with broader information. Still, the Edge article is worth reading because he speaks so very clearly on such complicated matters that I couldn't help but understand him. My guess then is that Moore's law will continue to be followed, but the computational medium will change. Someone's already asked what we would do with infinite computing power, but will quantum computation be something truly infinite? Or is all computation just another way to measure reality? The American Scholar article says:

Quantum theory is not just being used to look at questions about information; it is being recast as a theory about information. And that reformulation fits with a view, shared by many in the field, that computation is not just something that we do with the universe. It may be something universe does itself. This may be the link between being in the world and understanding it, between following a physical law -- falling down, say -- and calculating how that physical law is followed. It's almost as if the law is a result of the way the universe itself does some similar calculation.

Deutsch has seen the future, and it is qubits. There is already quantum cryptography; there may be actual quantum-based computers not so far away. And they may not involve falling over.

More Quantum Computing links:
A Scientific American article
Department of Computing, Imperial College, London
Dave Bacon's page of links and quips

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Related Links
o recent article
o Edge
o Gaia hypothesis
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o A Scientific American article
o Department of Computing, Imperial College, London
o Dave Bacon's page of links and quips
o Also by iGrrrl


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Qubits in your future | 50 comments (49 topical, 1 editorial, 0 hidden)
Obviously... (2.18 / 11) (#2)
by Zeram on Mon Dec 04, 2000 at 02:36:58 PM EST

You've never spent much time in the wilderness, or for that matter ever truely attempted to fathom the nature of conciousness. When you strip all the wonder out of life and look at the pure logic, it's pretty baren.
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actually... (4.16 / 6) (#5)
by iGrrrl on Mon Dec 04, 2000 at 02:55:33 PM EST

You made an incorrect assumption on both counts. I like the woods and spend a lot of time in sailboats. I'm a biologist specifically because Nature is just so coool that the attempt to fathom comprises both my professional and personal life.

As for attempting to fathom the nature of consciousness, I'm specifically a neurobiologist for that reason. I got interested in quantum computing and quantum mechanics because of some fairly (to me) silly ideas about the quantum nature of consciousness. There are people who think that structures in the neuron called microtubules carry quantum computational information, and that what we call consciousness is the wave-function collapse at the microtubule level. (info here) Having been initially trained as a cell biologist with a specialization in cytoskeleton -- of which microtubules form a major part -- I have a hard time with the notion of specific quantum states along the largest of all biological macromolecules. My bet for quantum states influencing consciousness has more to do with the level of synaptic transmission, and the stochastic (rather than binary) nature of most of the neural connections in the brain.

In fact, I originally was going to tie the two interests together, but it seemed a bit far fetched. Eventually I'll put a rebuttal to the microtubule theory of quantum consciousness on my home page, but not right now.

Logic is not, to quote Spock, "A wreath of pretty flowers that smells bad." It is merely one possible way of looking at the flowers. I try not to limit myself to any single perspective, and happily stop to admire the beach roses as well as wonder about the chromogens that cause them to reflect that specific set of wavelenghts of light.

--
You cannot have a reasonable conversation with someone who regards other people as toys to be played with. localroger
remove apostrophe for email.
[ Parent ]

Ok, (2.00 / 2) (#13)
by Zeram on Mon Dec 04, 2000 at 04:01:15 PM EST

So you have me there. But I think you concentrated too much on my words, and not enough on my meaning. When your on the beach in the wee hours of the morning, just as the light is starting to make it's break over the horizon, what do you see?(Note, I don't mean what do you see with your eyes) Or if your in the forrest completely surrounded by nothing but life itself, what do you feel? The point I'm getting at is that science has yet to explain why I know that a certain person is going to call me two seconds before my phone rings and it's them, or for that matter how I can complete the sentances of people I really care about, and even know exactly when they are thinking of me.

Also, while I don't fully understand what you are saying (I'm no scientist, I'm just a guy how sits around and ponders life) I think I get your point and agree with you. If I follow you, then it makes sense to me that there is a Quantum reaction with an electrical transmission, not with a molecule.
<----^---->
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[ Parent ]
Actually... (3.66 / 3) (#16)
by a clockwork llama on Mon Dec 04, 2000 at 05:56:40 PM EST

> The point I'm getting at is that science has yet to
> explain why I know that a certain person is going to
> call me two seconds before my phone rings and it's
> them.

Actually, it has. It's called selective recall, and is a psychological phenomenon rather than a physical one. It works like this:

Every so often, you think to yourself: "hey, maybe Bob will call." Most of the time, Bob doesn't call after you have this thought, and you'll forget that you ever did. But once in a very great while, just out of pure coincidence, Bob will call you. You'll be elated, and think to yourself: "Hey, what were the chances of that happening?" Because correct predictions tend to be remembered and incorrect ones forgotten, you'll soon start believing that you're psychic.

(In fact, a very similar psychological effect is a problem in science. When scientists get an experimental result that doesn't look right, it's often tempting to throw it away, rationalizing it as a random bleep. But this skews the experiment, and tends to reinforce bad results. Historically, this has led to problems.)

Of course, like all scientific theories, this explanation can be disproven by experiment. All you have to do is keep some paper handy, and make a note when you think someone is going to call you. If you're really psychic, then there will be some correlation between your predictions and the results. In that case, you'll be a million dollars richer.



[ Parent ]
Well... (1.00 / 1) (#23)
by Zeram on Mon Dec 04, 2000 at 11:04:54 PM EST

Then I guess I'm going to be a million dollars richer.
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[ Parent ]
Aesthetics in Science (4.50 / 4) (#17)
by Mad Hughagi on Mon Dec 04, 2000 at 05:57:45 PM EST

Perhaps a Quote by the late R. Feynman will illustrate why it is somewhat naive to believe that science takes away from the aesthetics that all humans enjoy:

"The stars are made of the same atoms as the earth." I usually pick one small topic like this to give a lecture on. Poets say science takes away from the beauty of the stars -- mere gobs of gas atoms. Nothing is "mere." I too can see the stars on a desert night, and feel them. But do I see less or more? The vastness of the heavens stretches my imagination -- stuck on this carousel my little eye can catch one-million-year-old light. A vast pattern -- of which I am a part -- perhaps my stuff was belched from some forgotten star, as one is belching there. Or see them with the greater eye of Palomar, rushing all apart from some common starting point when they were perhaps all together. What is the pattern, or the meaning, or the why? It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined! Why do the poets of the present not speak of it? What men are poets who can speak of Jupiter if he were like a man, but if he is an immense spinning sphere of methane and ammonia must be silent?" - Richard P. Feynman (1918-1988)

There is also a quote more directly related to beauty in nature that he had made, however I can't seem to find it anywhere. In the end I don't think being more knowledgable about anything can ever reduce it's beauty. The bliss that can be found in ignorance can equally come from curiosity.


HUGHAGI INDUSTRIES

We don't make the products you like, we make you like the products we make.
[ Parent ]

Hm... (none / 0) (#28)
by Zeram on Tue Dec 05, 2000 at 10:19:41 AM EST

I think you missed my point as well. I'm not speaking to the aesthetics of nature. The basic point I am trying to get at is this: What is so wrong with attaching mystical trappings to the Gaia hypothesis? Is it so hard to believe that the Earth is more than the sum of its parts? And that being so (and humans being what they are) shouldn't there be some way of describing that greater part?

I know that the rebuttal for that is that it's illusion, mental trickery, and that it contains very little in the way of facts. But facts don't tell the whole story and I don't believe that they ever will. There will always be phenomenon that science can't (or wouln't) explain. "There are more things under heaven and earth..."
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[ Parent ]
Sorry (none / 0) (#29)
by Mad Hughagi on Tue Dec 05, 2000 at 11:12:30 AM EST

I did miss your point (it wasn't stated!).

I do in fact believe that the universe (including the Earth) is more than the sum of it's parts. It is also equally described by the interactions and processes that the parts follow and probably a myriad of other ideas that we have yet to truly grasp. Whether you would like to think of it as simply being above humans (mystical) or whether you would like to investigate it in an attempt to truly understand it is ones own affairs.

If you would like to look at it from a philisophical standpoint, the facts (perhaps they would be better termed as information) are all we have to describe our reality. If we don't get all the facts (which I agree is a pretty much infinite task considering just how much really goes on outside of our normal sensory perception) then all we are doing is approximating the 'true' reality in a way which it is comprehensible for our limited abilities.

While it might be true the science may never describe every phenomenon, I don't see how that should be any hindrance to exploring our reality. If a few mystical hypothesis are found to be true on a scientific basis along the way, I don't really see that as being such a bad thing. If it is still mystical to you in light of scientific progression then I don't see why anyone would be concerned. Isn't mysticism all about the subjective experience anyways?


HUGHAGI INDUSTRIES

We don't make the products you like, we make you like the products we make.
[ Parent ]

Exactly (none / 0) (#34)
by Zeram on Tue Dec 05, 2000 at 02:04:11 PM EST

Facts are not the only things we have to describe reality. Science happens to be the most commonly accepted way of defining reality, but it's not the only way. It is my personal belief that life is only as objective as you let it be.
<----^---->
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[ Parent ]
"Facts don't do what I want them to." (3.66 / 3) (#39)
by iGrrrl on Tue Dec 05, 2000 at 07:21:44 PM EST

Science happens to be the most commonly accepted way of defining reality...

From my perspective as a scientist, a minister, and an esotericist I would have to disagree. Try this:

Science happens to be the most commonly accepted way of measuring reality.

There is an unsubtle difference in these statments.

--
You cannot have a reasonable conversation with someone who regards other people as toys to be played with. localroger
remove apostrophe for email.
[ Parent ]

There is a difference... (none / 0) (#43)
by Zeram on Wed Dec 06, 2000 at 09:20:57 AM EST

But I still stand behind what I said. Why measure reality, if not for the purpose of defining it? As I am sure you know, raw measurements mean little with out some sort of analysis. The analysis is the important part, because that is where science says A+B=C and that's it period end of story. I'm not saying this is a bad thing, theories beget theories, laws prop them up, it's all very logical. As theories and laws come along they begin to create a picture of our world based on the things that are not generally visiable to the "naked" human eye. Let me illustrate my point:

Science is not content to just say that I am experiencing 1g right now, it goes on to define gravity, and to eplain how the interaction of masses creates attraction.

If science was about measureing reality, then scientists would not delve into the how/why of things. I think that even you can't really say that you'd be fully happy with knowing only what happens without knowing how it happens and why it happens. And getting back to my origonal point this is where scientists generally make a big mistake, they see science as absolute and exclusive. Or to put it another way scientists see life as "there is one truth and it's name is physics (biology, math, so on and so forth)." In a sense you are right, facts don't do what you want them to do. Facts are facts and if they don't support your ideas, then it's your ideas that are at fault and not the facts. How ever in another sense you are wrong, the facts will always support an objective model of reality that says that my subjective experience is wrong.
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[ Parent ]
expansion on the soundbite (4.00 / 3) (#45)
by iGrrrl on Wed Dec 06, 2000 at 03:10:13 PM EST

Well, we've ventured 'way off the topic of quantum computing, but 'way into the topic of consciousness.

Several responses:

Science is not content to just say that I am experiencing 1g right now, it goes on to define gravity, and to eplain how the interaction of masses creates attraction.

Without defining g (and gravity), there is no meaning in saying, "I am experiencing 1g right now." In defining gravity -- and what can be measured about it -- one can attach the lable "subject to 1g" to any mass at sea level. "Experience" implies perception -- do you percieve different amounts of gravity with the same sort of accuracy that you could say, "That color is fire engine red"?

If science was about measureing reality, then scientists would not delve into the how/why of things.

Actually, science can only answer questions of how. Matters of why are metaphysics. A scientist can address questions of how by measurement and by experiments (the reasults of which are expressed as measurements). That is all. No Why answers here, and none pretended.

Or to put it another way scientists see life as "there is one truth and it's name is physics (biology, math, so on and so forth)."

It is my considered opinion that to see anything as the one truth is, um, stupid and limiting. By "anything" I could include science, fundamentalist religions, anti-religions, and sports fanatics.

Facts are facts and if they don't support your ideas, then it's your ideas that are at fault and not the facts.

Point correct. Or to be facetious, "Well, duh." (FYI, I was quoting lyrics from a favorite Talking Heads song off the disc Remain in Light.)

How ever in another sense you are wrong, the facts will always support an objective model of reality that says that my subjective experience is wrong.

Well, it may be that in your perception and subjective experience, anything I say will be "wrong." So be it. However, there are many truths. If one is tripping on acid and percieves the walls as breathing, other people's perceptions (and a physical measuring device) will likely disagree. So what? Perceptions are very slippery things, even simple things like physical description and recall of traumatic incidents. Two eyewitnesses rarely tell the same story. Unless there is an independant device, say a video camera, a third person cannot know which of them is telling the "truth." For each witness, though, their memory is "truth."

Nothing is True. To quote myself from a recent post to the Art With Brain in Mind list:

"Truth is a slippery thing, and I find shades of meaning of the word. Religious truth is not the same as scientific truth. ... Scientific truth is based on repeated observations and consistant results. As the measuring tools get better, truth can change. In addition, there are several functional truths which can easily co-exist. Newtonian physics is perfectly good for ballistics, but completely useless for quantum mechanics. Quantum computation could do for ballistics, but it is more efficient to use the Newtonian shorthand."

In this forum I speak primarily as a scientist, but you know nothing about me or my total worldview except what you have projected based on how my written words filter through your perceptual set, your filters based on your prior experiences and unconscious prejudices. Which is fine with me, but please consider that you might make a mistaken assumption that the facet presented represents the whole.


--
You cannot have a reasonable conversation with someone who regards other people as toys to be played with. localroger
remove apostrophe for email.
[ Parent ]

Point taken... (none / 0) (#46)
by Zeram on Wed Dec 06, 2000 at 04:13:26 PM EST

I hope you don't think I was attempting some sort of personal attack. You are right in that I know virtually nothing about you. And yes I am interpreting what you say through my own personal, subjective filters. However when I see someone say something like: "...he takes the 'many universes' idea of quantum mechanics, and strips it of its possible mystical fantasies. (I like this particularly because of the mysticism the non-biologists sometimes attach to the Gaia hypothesis.)" That could mean several things, the most likely interpretation of that quote (with the fewest filters applied to it) is that you hold little if any stock in the "mystical". However the term mystical I think is where I got tripped up. To me mystical is pretty much anything beyond direct human experience that is unexplainable. I see now that that is not neccessarily what you were talking about, and I think that you were more refering to the crackpots and whack-jobs that make people who have attained levels of serious enlightenment look bad. All I can say is that all I have to go on is your words, and my reponses were in an attempt to make a point, not an attack, and I appoligze if it seemed like the latter. I do also admit that I made a brash generalization, that was incorrect, and I appologize for that as well.

But on to my responses! =) I can say that I am feeling one zorton right now, and with out any sort of definition have it mean the same thing as saying I am feeling 1g right now. Will anybody understand me? No. But thats not the point, I can make arbitrary observations and have them be totaly valid (not that I would, it's just that it's possible). In doing that I have measured a peice of reality, but not defined it. No scientists worth his degree would accept my oberservation because there is no proof, and well proof requires definition. And it is through this proof that scientists explain the why of things: "Why does the sun rise in the east and set in the west?", "Why do stars go supernova?", "Why do cells perform mitosis?".

Once again I agree with you that limiting oneself to one "truth" is a very bad thing, however ask yourself, how many of your collegues believe in anything beyond science? While I don't know for sure I would be willing to bet that it is a very small number. I tend to travel in educated circles, and I have met many scientists, and have found that almost none of them believe in anything beyond what science can absolutely prove. I am not saying that there are not exceptions, maybe even broad ranging ones, perhaps I have just met all the wrong people (and let me just say that it is heartening to know that there is at least one scientists that does not believe that truth is absolute).

I do not believe in truth, or in absolute anything. Reality is much more expansive and elastic than many people give it credit for, and I just really wish more people would come to recognize that fact.
<----^---->
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[ Parent ]
Your basic point (none / 0) (#31)
by leviathan on Tue Dec 05, 2000 at 01:04:16 PM EST

What is so wrong with attaching mystical trappings to the Gaia hypothesis?

IMO there's nothing wrong with attaching any meanings, observations, perspectives on to the Gaia hypothesis, except for the fact that what you end up with is no longer the Gaia hypothesis.

It may be very worthy to reevaluate the hypothesis as giving real human attributes to the planet (to take one very concrete example). It's a powerful poetic metaphor which has helped sell green ideals to the public.

There are many other things you can do with your interpretation of the hypothesis, many deeply personal and revealing, but to say that any of these things are part of the original hypothesis is simply disrespectful to James Lovelock, and obscures the work he did and the point he was trying to make.

--
I wish everyone was peaceful. Then I could take over the planet with a butter knife.
- Dogbert
[ Parent ]

Yes (4.00 / 1) (#35)
by Zeram on Tue Dec 05, 2000 at 02:08:01 PM EST

You have a point, I was trying not to be so specific, but I had to, to properly express my point. And you are correct, in that calling it the Gaia theroy at that point is being disingenuous.
<----^---->
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[ Parent ]
Actually... (none / 0) (#37)
by leviathan on Tue Dec 05, 2000 at 03:05:08 PM EST

Checking back, your two points (the original comment, and what you termed your 'basic point') are different.

I disagree with your basic point in two ways, pedantically (as you've just cleared up), and that if you're looking for something deep, Science isn't the place to be looking.

Science has never really had anything much to say about beauty (it might have detected some portion of the brain that detects it, but has never said what it is). Science deals with stuff that you can give a yes or no answer to (can it be proven? yes/no).

That was my response to your first point. There are many tools for you to use; art, zen, religion, meditation, or copious quantities of mind altering drugs ;)

--
I wish everyone was peaceful. Then I could take over the planet with a butter knife.
- Dogbert
[ Parent ]

The thing is... (4.00 / 1) (#38)
by Zeram on Tue Dec 05, 2000 at 04:08:52 PM EST

I was trying to make a general point, but make it clearer, I brought up the Gaia theory.

Science and art have been converging in modern times, a good basic example of this is fractals. A fractal screen saver is great to watch under "altered states of conciousness" ;) and yet at the same time pretty interesting mathamaticaly.

I realize that science is pretty much about yes or no, but it doesn't have to be. The problem is it's a fine line to walk between a turely subjective experience of reality, and just making random stuff up. There in lies the beauty of quantum mechanics, it takes the rigid yes or no of science and adds a maybe. And eventually that maybe will get "science" to understand that subjective experience is not less valid, just because it's less factualy explainable.
<----^---->
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[ Parent ]
Yes:No:Maybe:default: ? (none / 0) (#40)
by leviathan on Tue Dec 05, 2000 at 07:37:32 PM EST

<p>The central point of this, I guess, is that our thought processes are one thought following
another. Whereas the scientist (or mathematician) restricts the thought he can have by logic, the
classical artist restricts them by aesthetics, or classical ideas of beauty.
<p>Fractals are a case in point. The people that first devised fractals weren't looking for
pretty pictures AFAIK. It was different people acting on different instrincts which made them into the
screensaver you see.
<p>I suppose the closest that we've ever got to a true mix between scientific instrincts and artistic
ones is computer programming. The algorithmic side of what people write is all about speed and
clarity, and can be measured, yet some artists are using programming as a tool. I guess it's probably
because programming is not only an application of science, but a science in itself; it's got
much of the flexibility of a rigorous science, but is much more forgiving in allowing people without
a formal bacground to get started. It's far easy to write a simple program than devise a brand new
fractal algorithm, or at least one with any particular aesthetic worth.
<p>Ok, ramble over...back to work.

--
I wish everyone was peaceful. Then I could take over the planet with a butter knife.
- Dogbert
[ Parent ]
Aargh! Sorry (none / 0) (#41)
by leviathan on Tue Dec 05, 2000 at 07:43:49 PM EST

In my defence, I can only state that preview doen't work in this browser :(
Humble apologies to anyone foolish enough to try and read that comment without widening their browser window!

--
I wish everyone was peaceful. Then I could take over the planet with a butter knife.
- Dogbert
[ Parent ]
Programming (3.00 / 1) (#44)
by Zeram on Wed Dec 06, 2000 at 09:24:17 AM EST

Is definitely another good example. The thing about fractals is that even though the origonal people who discovered them did not neccessarily want to find pretty pictures, but people have gotten interested in the math of fractals as a result of the aesthetics of fractals.
<----^---->
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[ Parent ]
The beauty of science (none / 0) (#47)
by dennis on Wed Dec 06, 2000 at 05:14:22 PM EST

Nonscientists tend to see science as very cut-and-dry, rationalistic. In school we learn about the "scientific method," and it's often presented as a rather plodding exercise. But the best scientists, especially among physicists, tend to see it differently. There is an aesthetic to science. Mathematics can be beautiful, in much the same way that music and art can be beautiful, although it's so abstract that it's hard for non-mathematicians to understand. (I'm no mathematician, but I took enough math to get a glimpse of it.)

And the really odd thing is, the most beautiful theories in physics turn out to be the ones most likely to be true.

[ Parent ]

Different thing IMHO (none / 0) (#48)
by leviathan on Thu Dec 07, 2000 at 08:20:03 AM EST

Yes, I agree - a neat theory or algorithm can be beautiful, but the reason I believe it is so is that it triggers responses in your head that say "Yeah, I'm on the right track". And when you do get to the right answer, that's reinforced. It's like, "I've got a good feeling about this one.".

I know this most from coding; something looks nice to me when I know I can debug it easier, most often. When I know it's right just from looking at it. But I did extra maths up until I was 18, and a right-looking equation is just the same

But with actual sensory aesthetic beauty, is there any feedback to reinforce those ideas? Maybe there's the influence of society there (which, considering different societies ideas of what is beautiful, looks likely) but I'd like to think there's something more there...a great symphony is great whether or not anyone else agrees with me.

--
I wish everyone was peaceful. Then I could take over the planet with a butter knife.
- Dogbert
[ Parent ]

Anthropology (5.00 / 1) (#50)
by dennis on Thu Dec 07, 2000 at 11:31:25 AM EST

Although I took a lot of math I got my degree in anthropology. The basic methodological assumption is that nothing is common between all cultures (which is not the same as thinking that there really is nothing in common, it's just the starting point so you don't make invalid assumptions). But somebody did an interesting experiment:

They went to seven widely varied cultures, and asked people in each one to identify their greatest artists, and some mediocre artists. They collected artworks from each artist, showed people in each culture the artworks from the other six, and asked them to identify the great and mediocre artists in the foreign cultures.

What they found was interesting. The non-artists and mediocre artists couldn't tell the difference between great and mediocre foreign artists. But in each culture, the great artists could identify the great artists in the other cultures. Apparently, there is a universal human standard of great art, but you have to be a great artist to pick up on it.

[ Parent ]

Yes, but... (none / 0) (#49)
by Zeram on Thu Dec 07, 2000 at 08:47:04 AM EST

Even for scientists that look out side of the "scientific method" they still have to come back to it. There still has to be formal proof, research backed up by a repeated (and repeatable) experiment. Inspiration is fine (I'm a big fan of searching odd places for inspiration) but eventually there have to be cold, hard, logical facts.
<----^---->
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[ Parent ]
This is one of those things... (2.20 / 5) (#3)
by trhurler on Mon Dec 04, 2000 at 02:41:57 PM EST

that suffers from a common malady: few people understand it, but it is so compelling to many of those who think they do that it is widely discussed. Deutsch is a very smart man, but do understand something: nobody, and I do mean nobody, really understands this stuff yet. Not one person on this planet can tell you how to construct a useful machine from qubits, nor can anyone demonstrate that it is actually possible to do so. It is not my purpose to malign the work of those who are pursuing this field; I wish them the best of luck, but I do think the amount of publicity this topic receives is entirely out of proportion to the results it has generated thus far. Keep in mind that cold fusion was supposedly farther along than quantum computers currently are when it became a laughingstock.

That said, all the mumbo-jumbo about everything being a calculation and the laws of the universe being tied to calculations and so on is the sort of semicoherent rambling you get when otherwise intelligent and sensible people spend way too much time every day day after day immersed in one particular very specialized field without taking much in the way of breaks; it is ironic that you mention the mumbo-jumbo most people associate with the Gaia theory, because in fact, THIS is the mumbo-jumbo associated with quantum computing. Quantum mechanics in general has always had a lot of good math and a lot of really bad interpretation, though; I can't fault Deutsch too much for continuing that tradition somewhat uncritically.

--
'God dammit, your posts make me hard.' --LilDebbie

It's worth noting... (3.75 / 4) (#6)
by dennis on Mon Dec 04, 2000 at 03:03:28 PM EST

...that IBM has built a working five-qubit quantum computer. Certainly there are major engineering problems yet to be solved to scale it up and make it practical, but it's not as if it's pure theory. Unlike cold fusion, the results can be replicated, and they don't contradict known laws of physics.

[ Parent ]
Holy moley! (3.00 / 1) (#9)
by fluffy grue on Mon Dec 04, 2000 at 03:22:42 PM EST

The fact they made a 5-qubit computer doesn't surprise me. The fact that it does something as cool as determining the order of a function - and in only one step - now THAT is just plain cool. That's the sort of thing I'd have never thought to be even computable...

I'm suddenly quite looking forward to quantum computers. :)
--
"Is not a quine" is not a quine.
I have a master's degree in science!

[ Hug Your Trikuare ]
[ Parent ]

Order of a function (4.00 / 1) (#10)
by trhurler on Mon Dec 04, 2000 at 03:34:15 PM EST

Obviously, since humans can determine the order of a function, it is computable given some sort of machine. However, I agree that it is cool that they've found one other than a human brain that can do this. I'll still stand by my claim about the state of quantum computers, though, because building a 5 qubit toy does not demonstrate that it is possible, even in principle, to build the machines people are hoping for; the construction methods used not only would not scale to such a machine, but would run into fundamental barriers rather than practical problems. Again, this is not to say it can't or won't be done, but only that we, as people not involved in the research itself, cannot usefully do more than speculate about it at this point. Speculation is fun, but it also has an element of the locker room rumor to it; people tend to forget that they're speculating. Just keep that in mind when you hear people talking about quantum computing in tones that suggest factual information.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Okay, clarification time... (none / 0) (#25)
by fluffy grue on Tue Dec 05, 2000 at 03:35:47 AM EST

Are we talking about order of complexity of a function (i.e. O(n^2)), or some other property I'm not aware of? As far as silly theoretical computer scientist me knows, you can (in general) only determine the order of complexity through symbolic means, and even then it's still a lot of guesswork and symbolic proofs, rather than anything automatic, except in a few notable exceptions (e.g. simple polynomials and not-too-complicated logarithms). Even with the inherent parallelism and fuzziness of quantum sets, I don't see how they'd go about inputting general-purpose equations in the capacity needed to numerically derive the order (hint: n0 is somewhere between 0 and infinity).

Then again, last time I tried getting into quantum mechanics I got completely overwhelmed and spent a few years thinking I was a porcupine. Maybe I should just leave this stone unturned...
--
"Is not a quine" is not a quine.
I have a master's degree in science!

[ Hug Your Trikuare ]
[ Parent ]

You know... (none / 0) (#36)
by trhurler on Tue Dec 05, 2000 at 02:09:39 PM EST

the funny thing is, I'm not entirely certain now that you mention it. I assumed they meant order in a mathematical sense which I do not quite recall clearly enough to state it, but the only reference I found from IBM was basically a PR flack yabbering about a subject he or she knows nothing at all about, and which I am fairly certain that conventional computers cannot determine in any reasonable period of time.

By the way, it is certainly possible to determine O() using numerical methods, but it obviously is slow and I'm guessing that it basically would never be the sensible path to take. Similarly, computers can and do perform general symbolic manipulations; theorem provers are a really cool area of CS, although they're also somewhat esoteric and I don't claim to know much about how practical ones actually work.

--
'God dammit, your posts make me hard.' --LilDebbie

[ Parent ]
Theorem provers and numerical O (none / 0) (#42)
by fluffy grue on Tue Dec 05, 2000 at 07:47:51 PM EST

Theorem provers are symbolic manipulation, and involve a lot of AI and branching guesswork and the like. That's not in the realm of a hard quantified algorithm, which is (IIRC) what qubits are good for.

Unless I'm grossly mistaken, numerical methods don't PROVE order properties, they can only show that "given this input data, we can extrapolate such-and-such polynomial complexity and guess that it therefore has polynomial order of 'blah'." Things like that break down for things like, say, determining the order of sin(x) - it's obviously and easily-provably O(1) but its polynomial order certainly isn't, and the wider range of data you input, the goofier its polynomial order gets. (IIRC, it expands linearly with the number of zero crossings, though it's been a long time since I've done anything like this.) To a lesser extent, anything like k^x break down as well, since k^x's order is always HIGHER than any x^k if k>1 - that is, unlike sin(x)=O(1), k^x will never be O(x^n). And these are just the first examples to pop off of the top of my head. :)

Granted, this is splitting hairs over speculations due to a bunch of marketing fluff, so we should just relax and take it for what it is - fluff.
--
"Is not a quine" is not a quine.
I have a master's degree in science!

[ Hug Your Trikuare ]
[ Parent ]

sorry... (3.75 / 4) (#8)
by iGrrrl on Mon Dec 04, 2000 at 03:18:18 PM EST

...I should have made it clear that the "mumbo jumbo" was not a quote from Deutsch, but rather from Oliver Morton, the author of the American Scholar article.

I think it's fun to let the mind range the possibilites, far-fetched as they might be. The trick is not to go so far that you can't do a focussed experiment.

--
You cannot have a reasonable conversation with someone who regards other people as toys to be played with. localroger
remove apostrophe for email.
[ Parent ]

Ad hominem argument; quantum "encryption" (4.00 / 1) (#20)
by sigwinch on Mon Dec 04, 2000 at 08:38:45 PM EST

That said, all the mumbo-jumbo about everything being a calculation and the laws of the universe being tied to calculations and so on is the sort of semicoherent rambling you get when otherwise intelligent and sensible people spend way too much time every day day after day immersed in one particular very specialized field without taking much in the way of breaks;...

And quantum electrodynamics is just mumbo-jumbo about the laws of the universe being tied to graph theory and statistics.  It's also correct, to something like 12 significant figures.  The format of a pop magazine interview provides little opportunity for diagrams and mathematical sybolism to properly explain a theory.  It is uncharitable, bordering on rude, to criticize the details of a theory on the basis of such an interview.  Moreover, making a weird assumption and carrying it as far as possible is the basis of most real progress in physics and mathematics.  General relativity, for example, makes fairly unmotivated assumptions about reality (the existence of space-time, its non-euclidian nature, the effect of an ineffable quantity called mass on space-time, and so forth).  As far as we know, those assumptions are internally consistent and not contradicted by experiment.  However, the original derivation was an exercise in metaphysics and deep imagination. 

Consider too that Deutsch is exploring poorly charted territory:  conventional quantum mechanics only describes the interaction of quanta with fields and with themselves.  Conventional physics assumes, for example, the existence of entangled pairs of particles, without asking how they came to be entangled, or how they become unentangled.  Deutsch is making the (perhaps unmotivated) assumption that quantum events obey meta-laws that are computational in nature:  that the occurrence or non-occurrence of an event is isomorphic with information, and that the rules determining whether a possible event happens are isomorphic with logic.

On the other hand, Deutsch is patently wrong about the so-called quantum encryption.  What is often referred to as "quantum encryption" is simply the exchange of session keys in a non-observable manner.  The session keys are verified using conventional digital signatures, and the payload data is encrypted using conventional ciphers.  Thus, the encryption is easily broken by a quantum computer.  True quantum encryption would require a cipher that can only be performed with a quantum computer, a cipher for which a quantum computer provides no advantage (unlikely, but who knows what lurks in the recesses of number theory), or a conventional cipher scaled to gigantic proportions (mega-bit-key DES).

--
I don't want the world, I just want your half.
[ Parent ]

I think you may be misreading Deutsch (none / 0) (#21)
by SIGFPE on Mon Dec 04, 2000 at 10:18:33 PM EST

Conventional physics assumes, for example, the existence of entangled pairs of particles, without asking how they came to be entangled
Methinks you know not the meaning of entangled. Every step in the process of a pair of particles becoming entangled is very well understood and predictions based on the theory work unbelievably well. What's not understood here?
Deutsch is making the (perhaps unmotivated) assumption that quantum events obey meta-laws that are computational in nature
Would you like to quote the lines where Deutsch says this. Pretty well everything Deutsch says about quantum computing lies within the current physics paradigms with nothing 'meta' anywhere.
SIGFPE
[ Parent ]
I've always thought... (2.00 / 6) (#4)
by Wah on Mon Dec 04, 2000 at 02:48:20 PM EST

of the human mind as a good example of a quantum computer. This is based on what little I understand of how some people think QCs will be used, and how quickly the mind can handle complex situations that simple calculation, even at great speed, could never touch.
--
Fail to Obey?
There is no evidence... (3.00 / 1) (#11)
by SIGFPE on Mon Dec 04, 2000 at 03:35:43 PM EST

...as far as I know that the human brain is a quantum computer. What ever gave you that idea? A physicist who knows nothing about neuroscience writing a book for the popular science press perhaps?
SIGFPE
[ Parent ]
Don't ask me... (4.00 / 2) (#14)
by Rand Race on Mon Dec 04, 2000 at 04:09:44 PM EST

... but iGrrrl, in an earlier reply, provided a quite informative link to a site that addresses this exact question in some detail.


"Question with boldness even the existence of God; because if there be one, He must approve the homage of Reason rather than that of blindfolded Fear." - Thomas Jefferson
[ Parent ]

THANK YOU VERY MUCH (none / 0) (#24)
by Wah on Tue Dec 05, 2000 at 01:35:36 AM EST

Sorry for yelling, but I just wanted to make sure you heard. I've been looking for such a link on and off all day. :-)

Now I need to read it, and update my own utter bullshit.

if it's not too much to ask, can someone moderate up my original parent comment. I would like to become trusted someday, but my attempts at humor and pet theories seem to prevent it. If it is too much to ask, don't do it, or tell my why.
--
Fail to Obey?
[ Parent ]

caution (3.75 / 4) (#30)
by iGrrrl on Tue Dec 05, 2000 at 11:25:09 AM EST

In the original reply wherein I put the link to Hammeroff's page, I also say, gently, that I don't think his ideas are at all correct. In fact, most people who actually do neuroscience (and are aware of his theories) think they're... funny. Both "ha-ha" and "peculiar."

I'd advise caution at adopting something that sounds plausible in a system about which you may know little.

--
You cannot have a reasonable conversation with someone who regards other people as toys to be played with. localroger
remove apostrophe for email.
[ Parent ]

noted (none / 0) (#33)
by Wah on Tue Dec 05, 2000 at 01:17:18 PM EST

I think it's fairly obvious now that I don't really know that much about it. I'm more interested in the philisophical rather than hard scientific aspects of the subject.

As a quick sidenote in that direction. I think it could be reasonably argued that a species trying to explain its own consciousness could be generally seen as both peculiar and "ha-ha". At least from someone who could have an objective opinion about it (i.e. not our species).

Anyway, thanks very much for the link. Whacky or not, I'll be reading it all week.
--
Fail to Obey?
[ Parent ]

Read some of the articles... (3.00 / 1) (#15)
by SIGFPE on Mon Dec 04, 2000 at 04:35:48 PM EST

...and note that at least they have the decency to admit that what they have isn't really evidence.
SIGFPE
[ Parent ]
Quantum computers (4.83 / 6) (#7)
by SIGFPE on Mon Dec 04, 2000 at 03:07:06 PM EST

This is a subject that I am very interested in.

The first thing I want to say is that the theory of quantum computing is very beautiful. It's a perfectly good alternative to Turing computation that is self consistent and it's a fun challenge to try to code for it. Several years back I wrote code to simulate Grover's algorithm and Shor's factorisation algorithm. The latter is very neat and anyone who's happy reading papers like this should read Shor's paper.

An important thing is that at least as far as algorithms go it's not more powerful than turing computation in the sense that and quantum computer can be simulated with a classical computer. On the other hand the time to simulate a quantum computer can grow exponentially with the number of steps and components rather than linearly for a classcial computer. So in principle they can't do more but can do stuff faster. (Quantum protocols are different - quantum encryption is something that can't AFAIK be done classcially.)

The down side is this: quantum computing is a lot like analogue computing. A naive person might think that analogue computers are the best way to solve differential equations because you get no numerical errors due to quantisation. But that's clearly incorrect: the difficulty of making analogue computers grows rapidly with the required accuracy because you have to manufacture more and more accurate components. This drawback is not shared by digital computers. In a quantum computer the state is represented by a bunch of real numbers (eg. a pair of complex numbers for one qubit). A complex quantum computer requires that these values are accurate and stable to many significant digits. Useful quantum factorisation requires unbelievable accuracy and seems quite impossible to me. I don't just mean difficult - maintaining 100 digits of accuracy in an analogue device isn't just difficult if you think about just how small 10^-100 is - it's unbelievably difficult. Any interaction with the computer's environment would ruin everything.

The reply of the quantum computer scientists is to point out the existence of quantum error correcting codes. These allow the repairing of errors due to interactions with the environment. These look like really cool techniques but they all assume interactions with the environment of a certain type and assume that other types of interaction have a strength of zero, exactly zero, not just 10^-100 units say. This seems pretty preposterous to me! Another approach is the concept of a 'decoherence free subspace'. This is an approach that sets up a physical system so that when you allow it to interact with an environment the total evolution of the system looks like a non-interacting quantum computer. But this requires a careful balancing act to make the external influences all cancel out and again it assumes certain types of interaction are unbelievably small.

It seems to me then that although a quantum computer might be able to perform exponentially more computation than a classical computer it suffers from the problem that it's exponentially harder to build making it no better than a classical computer for practical uses.

But I hope I'm proved wrong because quantum computers are cool! Unfortunately many physicists outside of quantum computing are as sceptical as me - it's just that they mostly don't bother publishing papers on the subject (though some do).

If you're interested in reading some of the real papers on this subject rather than the watered down fiction served up in the popular press try browsing arXiv. Understanding most quantum algorithms doesn't require much complex mathematical machinery - just some linear algebra. I wrote this 4 or 5 years ago and it may be of interest to some people. (The sample code is no longer available as it only compiles with Kai C++ - no use to 99.9% of people!)
SIGFPE
Re: quantum computers (5.00 / 1) (#18)
by claudius on Mon Dec 04, 2000 at 06:18:21 PM EST

I've only spent a small amount of time working in the quantum computing field, but I believe that you may be somewhat misinformed regarding the limitations of quantum computing. Quantum error correction has been demonstrated experimentally, and I don't think the limitations are as severe as you mentioned. The simplest schemes perform corrections when a single qbit interacts with a bath (in essence the interaction is a rotation about a single axis in an abstract space). However, more elaborate quantum error correction methods exist that can correct multiple "rotations." Interestingly, correction schemes even exist that permit errors being introduced during the correction stages themselves.

Other factorization methods besides Shor's algorithm exist; at least one of these can be done with purely rational (times pi) rotations so you don't have to keep track of so many decimals. Myself, I have worked on the problem of the universality of quantum computers that are fabricated purely out of gates that are rational number "rotations," gates which are much easier to prepare in the laboratory than computers that require you do a "rotation about axis "alpha" by an angle 0.1239832498234 pi." We have found that this is indeed possible, that universal quantum computers (up to a negligible overall phase factor exp(i delta) * identity_matrix) are reachable by a finite, experimentally realizable set of gates.

All opinions aside as to whether they will or won't work, the potential practical value of achieving quantum computation makes them worth investigating. Science, as you know, listens to the sceptics but doesn't believe them. "Trust, but verify." Reagan's favorite phrase....

[ Parent ]

Interesting (5.00 / 1) (#19)
by SIGFPE on Mon Dec 04, 2000 at 06:56:57 PM EST

Quantum error correction has been demonstrated experimentally
Yes - and I'm not in the least bit surprised for a handful of qubits. The same goes for decoherence free subspaces. But I am yet to be convinced that difficulty of building such systems doesn't grow exponentially. I don't think I've been 'misinformed' as my opinions on this are my own. I may be 'mistaken' however.

I've not heard about using rational rotations. Why are they easier to build? Do you have a paper I could read? I'm pretty sure the usual Shor algorithm already uses rational multiples of pi - it uses as N point DFT so it involves angles like 2pi/N.

All opinions aside as to whether they will or won't work, the potential practical value of achieving quantum computation makes them worth investigating
I guess I reluctantly agree. I think they're cool for purely theoretical reasons.
SIGFPE
[ Parent ]
References (none / 0) (#27)
by claudius on Tue Dec 05, 2000 at 09:26:32 AM EST

I don't have exact references at the moment. All I can find in my office now is a preprint of one of the papers, but you might check out e.g. Boykin et al. in the 1999 (perhaps 2000) Proceedings of the Foundations of Computer Science (FOCS). I think a version of the same paper also went to Information Processing Letters, but I'm unsure whether it has been published yet.

[ Parent ]
Question (none / 0) (#32)
by dennis on Tue Dec 05, 2000 at 01:12:11 PM EST

This is interesting. I'd always heard that adding qubits is just (!) a matter of keeping them from decohering. So for 100 qubits, you would use 100 electrons (or whatever). But each has only two possible states, it's still digital, although they don't have either state before you measure. Why do you need analogue precision to 2^100? Does this come in where you measure the output?

Personally, I'd still be interesting in looking at your sqrtnot.C code even if I can't compile it.

[ Parent ]

Capabilities of a general purpose Quantum Computer (3.66 / 3) (#12)
by Eray Ozkural on Mon Dec 04, 2000 at 03:46:32 PM EST

I'd like to ask a little question for CS people here. I'd read this quantum computing stuff a few years ago and I immediately thought "Hmmm, these devices look like they could solve NP-complete problems in polynomial time, since we should be able to construct a non-deterministic TM with it". In other words, my question is

* Theoretically, can a general purpose Quantum Computer be a non-deterministic TM in the true sense?

* Can such a general purpose Quantum Computer be built physically?

If the answers to these questions are "yes", then I can say that we'd go a lot further with these devices in many areas from computational sciences to sociology. On the other hand, these may turn out to be limited devices by nature and hence be used as components in larger computing systems.

I believe the recent solid-state breakthroughs were quite promising, but I haven't had the time to study their physics in detail. Could some of you give an overview of the state-of-the-art?

In fact, what this brings to my mind is whether non-deterministic PL constructs will actually gain popularity again. ;) I pity the grad. students after me, they will have to do "hypergraph partitioning on a parallel quantum computer". *<:)
__ exa
Yes. (none / 0) (#22)
by Alik on Mon Dec 04, 2000 at 10:20:10 PM EST

That's in fact the reason why they break current strong encryption; factoring products of big primes is believed to be at least NP-hard (but not proven, AFAIK). QCs don't care, and therefore we need quantum encryption.

The state of the art in terms of actual implementation requires mathematics which my puny human brain does not grok. Ask a physicist.


[ Parent ]
Physicists (none / 0) (#26)
by Eray Ozkural on Tue Dec 05, 2000 at 08:59:53 AM EST

These guys are causing a lot of trouble for us ;) Now I'll need to read some of those papers.

__ exa
[ Parent ]
Qubits in your future | 50 comments (49 topical, 1 editorial, 0 hidden)
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