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Computers That Solve Problems Without Being On
Iron Monkey writes: "Nature has this article about how quantum computers can theoretically solve problems without ever actually being turned on! Maybe California can use a few of these to solve their energy crisis - the ultimate in conservation."
It sounds like a novel from Douglas Adams or Terry Pratchett: You have to let the computer time not to run.
I wonder if I will be able to look at pr0n without actually paying...
Victor
This gives a whole new meaning to: "Let's not, and say we did!"
It seems like every week we have some new story about how quantum computers will break every known encryption algorithm, compress random data, slice break quickly and without crumbs, satisfy your SO's sexual needs, play Quake without human intervention, create a just and virtuous society, solve the halting problem, and compose sonatas all while locked in a safe covered over by drywall and abandoned for forty years in a mineshaft.
Delightful.
As any marketer knows, vaporware is the best product, because nobody knows its real limitations, only its theoretical ones. "There's no theoretical reason it can't sort a list in constant time... ergo it must be able to! Stop the presses!"
Call it vapor-state computing.
--G
I think it is you that shows a lack of understanding of physics. It's now universally decided that QM effects are not due to inexactness of measurement, but rather to the fact a particle does not have a definate position until the waveform collapses. Instead, it is a blurred out probability pattern. Even if we figure out a way to violate the uncertainty priciple, and pin down an exact location and vector, it won't give the particle a location until we measure it.
-David T. C.
If corporations are people, aren't stockholders guilty of slavery?
Full text at the LANL preprint archive.
Warning: requires some background in quantum computation.
Of particular interest is Chapter 6, where they say the following:
Our starting point was the enticing notion of being able to run a quantum computer `for free'. The quotation marks here were very necessary, however, for it is not at all clear what if anything comes for free. A CF protocol requires the computer to be present, and due time must allowed for the machine not to run.
They go on to explain why any attempt to use the times when the computer is "off" for other computation will ruin the original computation. The bottom line is that the story is fascinating and the model may be useful for analyzing various phenomena, but apparently this trick will not save any physical resources beyond "standard" quantum computation.
Of more pseudo-practical interest is the issue of interaction-free measurement (the "bomb testing problem" mentioned in the paper). For a nice introduction see The Tao of Interaction-Free Measurements.
... surely this heading refers to every computer ever made?
--
Matt
Matt
Mitchison and Jozsa's 'counterfactual computation' essentially taps into worlds in which the computer did run in order to extract the result into a world in which it didn't.
Once all the other worlds caught on, no one would be running the problem, so everyone will just sit there waiting for someone else to do their work.
--
Not really.
Think of it like setting a whole row of coins on their edge -- neither heads nor tails.
Yes, it takes energy to put them their in the first place -- just like it takes energy to create an entangled pair of photons to begin with.
Whack the table they are sitting on, and they drop over onto one side -- heads or tails. Measure the outcome.
In the normal Universe, whacking the table constitutes energy and your thus is your power source.
Your confusion arises from the fact that Quantum isn't the normal Universe. The act of observing the states causes the result.
In the end, technically, you are right. The act of observing itself imparts energy to the system -- thus is the power source. However, it is so small as to be unable to be measured by our current abilities. This results in the scientists not wanting to turn a 1-page article into a 30-page explanation of superposition, Heisenberg's Uncertainty Principle and other techno babble.
--
Charles E. Hill
Learning HOW to think is more important than learning WHAT to think.
I don't know if this solution will work in hot California, but here is a weird idea:
All the energy going into the CPU's are emitted as heat. This mean that having 300W of CPU's crunching data is equivalent to having a 300W electric heater oven turned on. Now, the obvious is, turn the oven off and start your computers.
Lets extend this to replacing peoples ovens with arrays of CPU connected to a common network. The result should be something like distributed.net or SETI@home network.
With this model all the energy 'wasted' in order to heat peoples homes could be put into good use cracking huge complex computational problems, or it could be distributed to home users.
Open for flame.
This technology could mean that the internet is not powered so much as quantum driven.
It highlights a meaning of the phrase "It's the little things in life that make the diffenence" and that won't be far from the truth.
Of course this is only a small step on a path which has been running for years, computing has been really pushing for speed. Especially when programmers had to account for each byte it used to squeze as much from a machine as possible.
This could also be useful in robotic technology where programmers always have to think of how long can the robot last before it has to get to the recharging station.
it's almost like having a mini power station in you computer.
You could imaging (although a little exagerated)
---
"Hey look Sir. No wires and it just runs and runs." says the inventer to his employer
"Can I take it home to test?" asks his boss
"Sure" replies the inventer "and dont forget it."
Next morning the boss returns "Well I can't believe it ran so long, it certainly kept the kids busy."
the inventor thinks 'bet they messed it up like usual'
"what was really odd was it really seemed to act strange." continued the boss "Well I guess it must be the quantum physics I remember the quantum world is supposed to have strange things in."
"Sir I think you'll find it's this loose wire. Thats why I don't test these things with the kids that quickly. They always fiddle with anything they can lay their hands on." cautioning his boss.
A sig is only as good as it's creator, that doesn't mean it is as good as it's creator.
Good point; I was inaccurate in my claim. My point was not particularly that I know more about quantum mechanics than the original poster; I suspect that I do, but only slightly so. My point was that his information about quantum mechanics was not accurate, and interested people should read further.
I don't think that I lambasted the original poster. He posted misinformation, I pointed it out. IMO, that's the point of having an open forum: I can post my bit of knowledge on something, and if someone else knows better, they can correct me. As you did.
BTW, I did know that entanglement doesn't give you complete knowledge of the other particle's state. AFAIK, only one part of the state (e.g. phase or angular momentum) will be entangled.
I still don't think my description was as inaccurate as his, but that my just be stubbornness speaking.
Nope.... in all superstates you've already failed your exams, so why even study? There is no superstate in which you passed your exam (although there is a superstate in which you passed out on your exam).
icanneverbereached@sogoaway.com aint my address.
Maybe the problem with Windows is that somehow they've managed to change h_bar so it is on the order of one and everyone is just experiencing macroscopic quantum effects, so it really is not Microsoft's fault.
Now all we need are project managers that conduct business in their sleep.. (and we all know how often that is).
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arcane for life
Is it me or did they basically say they can figure out a possibility among a set of large possiblities which do not include what actually occurred. Sounds useful. Probing all states? How long would that take? 40+GB of disk and a few hundred MBs of RAM doesn't sound like a quick probe.
I know, I know, I'm ignorant. The article did a poor job trying to explain this as anything but "some surrealist form of computer science".
Oh, and I can finally use this quote:
"In theory, there is no difference between theory and practice. But, in practice, there is. " - Jan L.A. van de Snepscheut
Fsck cluebie moderators. I'll say what I want, offtopic or not. And fsck having to qualify every bloody statement just
I'm not too sure I understand all of what you're getting at, so I'm not sure the story is actually relevent. It went something like this:
Folks fiddling around in a computer research lab working on quantum physics/chaos/computations stuff (oh, you know...;). They talk about spooky action at a distance, weird interlinks between representations of the universe (equations) and the universe (causal links I mean). Anyway, some dude is testing out the head professor's ideas, and suddenly the head prof notices that the weather has changed dramatically. Something about noticing how hot it has gotten in her lab. She looks out the window and realizes that the sun is a lot brighter than it should be. She also notices smoke in the distance. (!) Neat stuff. Maybe someone out there has read this and has some bibliographic info to supply? Hint hint.
____________________(
No, it means it's already done I Think Therefore I Am and got as far as deducing the existence of rice pudding and income tax before anyone managed to turn it ON!
I maintain that:
Chaos is the future and beyond it is freedom
In the spoon, there is no Soviet Russia!
An old computer of mine is already capable of solving problems without being turned on.
You see, there's this door in my house that won't stay closed... :-)
Super eurobeat from Avex and Konami unite in your DANCE!
Dr. Demento On The 'Net!
Then the halting problem can be solved too if you just use quantum computing to "pick" a solution out of the box. The problem is when you compare the solution to the initial problem and realize it doesnt work in *our* alternative universe. Why? in alternate universes you might have both solutions be the case, but not in ours.
I smell new theoretical problems brewing for quantum computing already
"Wireless : LAN
"The pianist goes through all the preliminary motions, but sits in silence for 4 minutes and 33 seconds -- after which, one assumes, the audience applauds. "
A musical number without any music, and an artist without an audience going through the motions without any instruments... *sigh* I'd say it sounds like my love life, only I have an organ.
Ceci n'est pas une sig.
Sorry.. whatever was I thinking?
Must be because I'm one of those damn Canadian types. Does anyone have any information as to whether conservation is uncanadian? I guess it must be, since we're the ones selling all this energy to California...
If my enemy's enemy is my friend, what happens if my enemy is his own worst enemy?
This must have something to do with the quantum superposition of the two submissions.
You see, the submissions were in a superimposed state until someone actually looked at them - at which time one of them was accepted, and one was rejected.
If my enemy's enemy is my friend, what happens if my enemy is his own worst enemy?
This is where my understanding of QC fails. Since your really not generating 'output' in the classical sense, but rather probabilities of the correct output. What happens when the most probable output is not the correct one?
Does a MC (modern computer) have to check the work of a QC in order to ensure the QC got it right? For example, instead of letting the MC use the Number Field Sieve algorithm to factor primes, the QC tells the MC what the most probable answer is, then the MC makes sure that this answer meets all the qualities of the correct result. This is obviously still a huge gain for factoring primes, but there have got to be a huge amount of algorithms wherein testing if the QC has the right answer would be more expensive than the MC just finding it on its own due to communication/conversion costs between the two different platforms/processors.
Will MCs need to check the work of QCs?
What's the use of solving the energy crisis if you don't need to turn on your computer to use it anyway :-)
Does this mean that Apple invented quantum computing?
As long as its only people in the parallel universes using circumvention software, then we can leave it up to that universe's MPAA to prosecute.
Just think, in a quantum scheme there may be a parallel universe where Jack Valenti is a benevolent benefactor to free speech. weird stuff, this many worlds theory.
"I Know You Are But What Am I?"
Actually, I rather like 4'33". The silence is genuinely eerie, and you end up hearing the absence of the music if that makes sense.
I suppose that the real purpose is the similiar to the strange physics of the article, or exploring the Antarctic; you might not want to experience the results of these musical experiments yourself, but its important that someone tries to find new things. Stockhausen isn't incredibly listenable either, but without these people we would never have found techno for instance.
"I Know You Are But What Am I?"
I'm sorry. I did not realize you were Canadian. As an American citizen, I am not allowed to speak to you because of your corrupting influence. This is our last communication. Goodbye.
If a quantum computer can solve problems without being turned on, what's next... a quantum SUPERcomputer that solves problems without even existing? Get me one of those!
"So on one hand, honey is an amazingly sophisticated and efficient food source. On the other hand it's bee backwash."
it doesn't run because ALL the other universes decided to fuck with us and not turn theirs on.
"Sometimes a woman is a kind of religion, she can save your soul & set you free from all your sins" - Bad Examples
On a quantum computer, you can get your frags out even faster and you don't need to power the thing on to find out your final score! I can hear the anouncer now...
"Fourty-two million frags in two seconds. Excellent! Please power up to start the game."
Blarf.
I wonder what the Intel adds will be like for now on...
Blarf.
So can we theoretically /. a site without ever visiting it?
Or can I first post without ever posting?
There goes the neighborhood...
The Blaster Master Fighting for Truth, Justice, and Evil Pie since 1979
If this doesn't sound like vaporware I don't know what does...
On the other hand, I often solve problems by procrastinating so long that there's no point in doing the task any longer. This may in fact be an optimal solution for many problems. Way to go, scientists, for figuring out something I knew instinctively when I was 12.
You see? You see? Your stupid minds! Stupid! Stupid!
For a fictional account of the far-reaching consequences of q-computing, try Permutation City by Greg Egan.
Let's say that a quantum computer can simulate the results of a computer twice its complexity which simulates a computer twice its complexity...
And the original computer doesn't even need to be on!
Now imagine the virtual worlds within it evolving.
That's just the tip of the iceberg in this story. Accepting the virtual q-computers is a big "if" to swallow, but it all hangs together beautifully.
Read it. Now, before it becomes reality and less interesting.
Joel
=Blue
LITTLE GIRL: But which cookie will you eat FIRST? C. MONSTER: Me think you have misconception of cookie-eating process.
Someday, we will build a computer so fast that it will instantaneously spit out the result of all computations we will present it with.
Instead trying to find answers for our questions, we will have to find questions for our answers.
Paul Anderson
"I drank WHAT?!" -- Socrates
In brief, you have to set the computation up so that only those computations that lead to the right answer interfere constructively. All the wrong ones cancel each other out.
The SCO lawsuit makes me wish my company were in Utah. We need a new building.
Michison and Jozsa describe a scheme for probing all the possible states of a quantum computer, including that in which all the 'switches' are 'off' -- that is, in which the computer is not turned on.
:-(
The bold bit is where my poor linear, state based brain fails. What's doing the probing? Won't that object have to be turned on? I don't understand.
Pinky: "What are we going to do tomorrow night Brain?"
Pinky: "What are we going to do tomorrow night Brain?"
Brain: "I would tell you Pinky but this 120 char limi
"Michison and Jozsa describe a scheme for probing all the possible states of a quantum computer, including that in which all the 'switches' are 'off' -- that is, in which the computer is not turned on." Just because your register is zeroed doesn't mean the chip is off. Not only that, but they essentially say the chip is off if one of its possible states is all zero.
What you say makes sense, but come on - never say never. Need I bring up the bloke at the US patent office at the end of the 19 century that thought everything had already been invented?
Perhaps you can deduce the future from the current quantum states of the objects around you?
Something will likely replace the digital computer someday, and you and I don't know what it will be.
And thanks, I will check out qubit.org
A pilot, in those days, was the only unfettered and entirely independent human being that lived in the earth.-Mark Twain
Simple, the entire program is loaded into Qbit-RAM and the program counter auto magically ececutes via a Qbit while-loop.
Finder of the any key.
So essentially, If I go out and buy one of these and turn it on, I'm only going to be doing processing for all of the neighboring worlds, so I'll always want to leave it off so that I can get some work done.
So wouldn't all of my other selves in all of the other worlds also want to leave it off to get work done too?
I mean really, who in their right mind is going to actually RUN their quantum computer so that we can all glean information from it across dimension?
We should be able to just figure out exaclty how improbable it would be for us to build this thing, feed it into a computer, and drink a nice hot cup of tea. poof!
I code, therefore I am.
All of this talk of quantum computers, and your post is titled, "the next step" instead of "the next leap"?!? I hate it when a perfectly good joke gets blown.
Virg
If quantum theorists are getting paid to write this kinda nonsensical prose I should be a millionaire.
For anyone interested in funding my research into quatum computing, here is a sample of my body of work:
While it is common practice to use "if, then" statements throughout contemporary programming, it shall become impossible to use these same conventions within the realm of quantum computing. In a quantum state "if" becomes iffy.
If x is true let y equal z
Clearly x is always true in the context of quantum theory. Given the infinite nature of the universe, the probability of all probabilities within an infinite area of space-time is also infinite. So then, let x always be true, or at least as true as anything else.
As the "if, then" process is paramount in most programs, quantum computing will be impossible to program for, or at least as impossible as anything can be in an infinite universe.
Okay gimme money now. Thanks, I've done my work for the day.
disc-chord
"Quantum computers are based on the concept of quantum entanglement, the ability..."
wurp replied: ... Don't spout off BS, and please, moderators, don't moderate it up!"
"What he describes is just called superposition; quantum entanglement is when two particles' quantum states depend on each other in such a way that once you know the state of one, you also know the state of the other.
I think it's saying something when he's written a few paragaphs of highly technical babble before 8 people around the planet could manage "FP!!!!!".
My .02,
My .02,
zencode
iactivist.org/jason
Please don't, because no one ever said any such thing.
Rather, let us apply a more appropriate Carl Sagan quote: "The universe is not required to be in perfect harmony with human ambition." It may be that the physical laws we have discovered actually represent limits to what we can do.
One day I feel I'm ahead of the wheel / the next it's rolling over me / I can get back on / I can get back on
and using quantum computers. (turned off, that is)
Doesn't anyone actually check these things before moderation?
Help find a cure for Gidget.
Perhaps the power companies can sue for "lost market opportunities".
Yes, but then it gives answers that aren't correct.
-B
Not that this wasn't entirely predictable.
out of your turned-off computer
but wait, how does your turned-off computer
spin up the hard drive to access data, or
store the data in RAM, or report the results
of its calculations?
i don't understand what the big deal is...
First of all, the article points out that current large scale quantum computers don't exist, and is only speculating on a system created in scale using the same two and three bit methods. It's quite a possibility large scale Quantum computers, if even possible, may be nothing like the three bit experiments of today.
Second, the 'computer' will still need to be on to extract any information. Work will still need to be done on what did happen in order to find out what didn't. All this article says, basically, is in the conclusion:
Mitchison and Jozsa's 'counterfactual computation' essentially taps into worlds in which the computer did run in order to extract the result into a world in which it didn't.
This seems to indicate that by reading in a specific way, you will be able to get what didn't happen, in, say, a function as well as the original output. So, if a function's only purpose is to set a bit to 1, then you will also have available what didn't happen, which in case the bit would also be 0. This all goes back to the superposition principle.
Now, what gets really interesting is expanding this into many millions of bits and very complicated functions. Essentially, you will also have available what you didn't do (not the inverse, but what didn't happen) as well as what happened. This will be very useful for cryptographic techniques, as well as very complicated mathematical operations. And as someone mentioned, it may be possible to have the computer generate a program and based upon all the possible outcomes in real and imaginary worlds, if you know what the output should be, you can select the best fitting program and it will write itself. Presumably, if programs could know what the outputs of other programs should look like, they could write new programs which do specific tasks without having to understand how programs are actually written. This could come in very handing for creating an intelligence and is very similar to what we do.
"I'll just chip in a bit for RedHat: I actually have that installed on my university machine." - Linus, '95
To be honest; I do not know everything about quantum mechanics, but why on earth would we want to turn those things on? If quantum computers are solely dependent on the laws of quantum physics (Laws we do not yet fully understand, btw) then it ought to be impossible to affect the computations, and no power is needed. That is unless we would like to receive the results in a way readable to humans.
If we figure out how quantum mechanics really work it should be possible to achieve this stuff, but I seriously doubt that we will get to see it before we are all dead.
After the "computer" has gotten it's input it should be able to continue to work without power (I imagine), and we wouldn't need power before we wanted to read the results.
I do not think that anybody will ask me to help them designing such a computer.
I wonder how they are going to program this computer, but I sure would like one of those
The quality of the stories on Slashdot really sucks these days. Combine that with a frightening lack of basic physics knowledge, and you have a recipie for disaster.
I expect the next story on slashdot will be the news that someone has invented a perpetual motion machine !!!
Wroot
Keeping Slashdot free of Beowulf jokes for 3 years.
Let's think about this:
.Net to this new platform and still charge everyone to use it?
Does this mean that Microsoft can therefore avoid porting
On the other hand, could this somehow render the GPL obsolete?
Can the RIAA still bust you for downloading mp3s if you used software that doesn't exist? And doesn't that somehow violate the DMCA?
Torg, come out of the spaceship. Nothing can stop Torg.
Offtopic reply :
I've got to say, that if and when the "internet 3" is around I might not like it. There is something to be said about enjoying those little weird interesting things and exploring it. Ever walk by stream and pick up a couple of rocks to skip. What would be the use or enjoyment if you knew exactly which one to pick. I think the thrill might be trying to guess.
Another thing would be exploration, when you don't know, everything looks interesting. I would hate to have a machine that could determine outcome, it would ruin the fun.
Also side note: in the late 80's early 90's Quantum computers was discusses alot in a magazine called ANALOG. and some people argues that quatum computing would be a 5th generation processor or language. Analong is anywhere from 8 to 12 years ahead in it's thinking. Great reading for those that might be interested in what the future might look like.
ONEPOINT
if you see me, smile and say hello.
I don't think religon enters into it. My understanding has always been that Albie was making an analogy, and that he didn't believe that the universe was inherently 'unknowable'.
No arguments with the rest of your comments. I have no doubt that he was weird, it seems the smarter you are, the wierder you are. Newton was a fruitcake, and Stephen Hawking is known to be a real pain at times (which must take a bit of effort).
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www.lucernesys.comHorizon: Calendar-based personal finance
i have a Mac IIci that already solves problems while it's not turned on, or even plugged in. it has no OS installed!
:)
the problem: my door keeps blowing shut when it's windy.
this could also be applied to a variety of other problems: i'm not tall enough to reach something, there's a burglar outside the window, my dog is teething, use your imagination!
p.s. - don't slag me for using a IIci for such purposes, i tested it against an old 386 and the Mac performed better. and as an added bonus - it complimented my decor!
www.pixelectric.com
Can we extend this to getting results from a quantum computer we haven't even built? Answers from the void?
We'd all just better watch out for those mice that want to cube our brains to get their results.
Hmm, HAL 9000 anyone?
TODO: Something witty here...
So what happens if everybody in all the parallel worlds decides to rely on somebody else in another parallel world having their qc turned on? Suddenly, all of the qc's in all the parallel worlds will appear broken?
GreyPoopon
--
Why is it I can write insightful comments but can't come up with a clever signature?
The question means the downfall of society, for if the question was known, we would not exist.
It would seem, based on the Heisenberg uncertainty principle, that our quantum computer will exist as a wave until we look at it. And even then we won't be certain where it is...
...so it's a good thing it can work without being turned on, because how are we gonna find the power switch anyway???
RC
RC
I am admittedly very uneducated in this realm, but it seems to me like this is a case of the emperors new clothes. It looks like a way for some incredibly intelligent people to sit back and watch as people believe that this computer is actually doing something with the power off.
I mean, just think about it. The machine is not doing anything. I might as well sit a block of ice on the counter, call it a quantum computer and say that it is in the process of solving complex calculations. IMHO it would have the same effect.
I feel like I am watching the Emperor walk down the street an nobody seems to care that his arse is hangin out in the wind...
DocWatson
MessEdUp
#/var/www/v
Wasn't this the computational unit that powered the "Heart of Gold" in the Hitchhiker's Guide? This is going to turn my desklamp into a grapefruit isn't it...
Now your Windows problems will crop up when the machine is off. You'll have to cycle power ON just to flush it out.
Which raises an interesting question... Is the segmentation fault really there untill we look at it?
Why do we even need to build one if we dont need to turn it on? If it supposedly gets the results by having it run in a "parallel" world, why not have it built in the parallel world as well? Seems like it'd be much easier that way.
Anyone read Timeline by Michael Crichton?
Why do we even need to build one if we dont need to turn it on? If it supposedly gets the results by having it run in a "parallel" world, why not have it built in the parallel world as well? Seems like it'd be much easier that way.
Anyone read Timeline by Michael Crichton?
And someone else didn't get it, and titled their story in nature after it. These quantum computers are off in the same sense that a modern "AND" gate is off if all its inputs are set to zero, which is to say, not off at all.
Denial isn't just a river in Italy
I mean, these could be as operating a circumvention device without your even knowing it. This, as the article implies, would be the result of people in parallel universes operating circumvention software, although I feel that this is something of an oversimplification of the way quantum mechanics work.
Denial isn't just a river in Italy
ha
How it would work is by getting the signal of the answer from a parallel world in the multiverse. You see, there are infinite universes lots like ours and lots unlike. So we build our QC and so does this happen in countless other worlds. We all make the same QC but in one world they turn theres on sending out the answer to all other QC that are looking for it. At quantum level the lines between worlds are blurred and because our QC is based on quamtum technology just as all the same QCs in other worlds all the universes are just using one computer at quantum level. The QC we made was on and got the answer just it happen in a parallel universe.
"In a parallel universe I am writing this same explanation...only there is has been proven" =)
Strange, how this all comes togeher so perfectly. Who would have ever thought, a computer that fixes its own mistakes. I would be very interested to see how it would work. I think once I am jsut curious, how big, and what does this beast of a machine look like?
Quantum computer? I guess they'll start building one once they're finished the hyperdrive.
Big deal. Take Ye Olde Quantum Two slit experiment. Cover one slit. The interference pattern disappears. Is that "counterfactual" or simple wave mechanics? Of course the particle doesn't need to hit the bomb; its wavetrain will, and create the interference whether the particle goes one way or another.
The obfuscation just kills me. It seems the more contorted the interpretation, the more likely it is to be published.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
The point is that this beam splitter arrangement is a simple interferometer. When the bomb is a dud, its mirror does not "measure" (interact destructively with) the photon wavetrain, so the interference pattern persists. If the bomb is set up to measure the photon, the interference pattern disappears. This is about the first thing people tried with the two-slit experiment.
Hence my question: is this configuration considered publishable? It's a no-brainer. It has no new physics, and adds nothing to the interpretation. It's a simple retelling of the old two-slit experiment, and it coins a new obfuscatory word to boot.
Here's my "counterfactual" experiment:
Set up two slits. Put a bomb with a (transparent) electron detector trigger over one of the slits. Do the two-slit experiment. If the bomb is a dud, the detector will not interact with the particles' de Broglie waves, and an interference pattern will appear. If the bomb is not a dud, the interference pattern will disappear (or the bomb will go off).
For each electron going through the apparatus, you have the same 50/50 chance of detonation if the detector is working. It's harder to measure the interference pattern, since you need more than one electron, but the mechanics are the same. You still have a non-zero chance of finding that the detector is working without activating it (if all the electrons go through the other slit, and you get enough to see that the interference pattern isn't there).
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
The same way a radio picks the "right" frequency out of all possible frequencies. An apparatus is set up which reinforces certain (De Broglie) wave patterns while allowing others to cancel out. When a stable wave pattern arises, the "answer" is embedded in the amplitudes at various spots.
Think of it as a very complicated resonator, which settles very quickly into a stable pattern of motion.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
Unfortunately most people don't understand that everything that's not measurable is religion.
Einstein mainly objected to the idea that QM, which is a form of statistical mechanics, is proof that the universe is inherently statistical and non-deterministic. While there's no reason why it couldn't be, there's nothing in QM to sway things one way or another.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
Yes, you've grasped the essentials of quantum philosophy - making statements about things which can't be observed. "Superposition of states" is just a fancy way of saying we don't know (and can't know) which state it's in between interactions. It doesn't mean that reality is that way.
---- "If we have to go on with these damned quantum jumps, then I'm sorry that I ever got involved" - Erwin Schrodinger
Then your algorithm/program is wrong, just like with conventional computers. From what I have gathered about quantum computing, the trick is to find an algorithm that will give the correct solution (or one of a set of correct solutions) with the propability 1 and 0 for all incorrect ones.
Okay. Let's see if I understand this correctly.
They're saying that because any quantum state in the computer can be reduced to the null state, an answer can be found before the computation is made. In other words, the quantum state you must input into the computer to program a calculation can instead be used to predict the answer.
If you know how to program a quantum computer, you theoretically can already know what the answer is.
Now, it may take more effort to derive the answer from the input states than to just plug it into the computer and let it churn away. So the computer itself will probably not be superfluous. But it's still an interesting theorem. It seems to be saying that programming a quantum computer will be approximately as difficult as solving the problem you want to program!
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
2001-05-02 17:56:53 Computing with the computer turned off. (articles,news) (rejected)
Best Slashdot Co
Can someone please explain to me how a quantum computer is made to pick a *right* answer out of all possible answers?
-jr
The only title of honor that a tyrant can grant is "Enemy of the State."
a computer turned off and solving problems.
My computer is off, and solves the problem of my backdoor falling closed.
Also, a computer that's turned off, and dropped from the empire state building on pauly shore's head solves a LOT of problems.
//rdj
No one can understand the truth until he drinks of coffee's frothy goodness.
--Sheikh Abd-Al-Kadir, 1587
Is a quantum computer that doesn't even have to be built to extract results from worlds where it was built and did run.
Although there might be minor limitations. But better not mention them, to avoid confusing the readers of nature. One of those limitations might even be, that you have to solve the problem (by whatever means) just to know how to extract and interpret the information.
The question is, does that quantum computer to be built and run in another world have to appear on a budget in this world, and where the money actually goes. But that will only be solved by quantum accounting.
"By the way if anyone here is in advertising or marketing... kill yourself." -- Bill Hicks
It isn't that a QC couldn't conveivably replace your desktop -- while it currently doesn't look feasable, a QC can emulate anything a classical computer can do.
However, there are some things that a QC doesn't do any better than a classical computer. In fact, most things, a classical computer does just as well as a QC. So the likelyhood of ever wanting to replace your computer with a QC is pretty small.
QCs have some real downsides that make implementing a general purpose one impractical or expensive. For one things, because of the no-cloning theorem (which states that you can't duplicate a quantum state without destroying the orignial), you cannot do a fan-out (connect one gate output to several gate inputs). There are ways around this, but I doubt it will ever be worth it.
Note that a classical computer is one that implements a turing machine, and a quantum computer is one that has a time-evolution operator given by the Schroding equation. "classical computers" implemented with silicon are obviously quantum mechanical devices. Classical computers will eventually have to face the quantum indeterminism of the extremely small scale, but they will still be classical comptuers -- even if they aren't implemented as silicon based semiconductors.
So does this mean if nobody looks at a Windows Box, it's got both UPTIME -AND- DOWNTIME?
Schrödinger 95, 98, 98SE, and ME. Going Down in TRUE RANDOM FASHION since day one!
"Everything you know is wrong. (And stupid.)"
"Everything you know is wrong. (And stupid.)"
Moderation Totals: Wrong=2, Stupid=3, Total=5.
Does this mean it's already done I Think Therefore I Am and got as far as deducing the existence of rice pudding and income tax before anyone managed to turn it off?
Smegma.
It's better than that: Nature summarise an article, then /. gives us a precis of the Nature article. According to the abstract of the original article, 'one can discover the outcome of [a] computation [...] without running the computer', and, of course, 'there are some limits on the information that can be obtained from them'.
Nature seems to have turned this into 'it should be possible to determine the outcome of a computation while the machine stays off', and not told us anything about what the limits are.
May be the Nature reporter didn't want to observe the original article for fear of collapsing its waveform.
It would be dead handy if they could extend their research to show that you don't even have to build the quantum computer in the first place. Hey, you probably didn't even need to know the results of the calculation, do you?
-- Andrem
There has been a major scientific break-in
preprint. It gives a pretty good account and should be comprehensible by somone who's done even a basic QM course - ie. it uses no fancy schmancy mathematics. Mod the parent up. Or read it here: Counterfactual COmputation
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-- SIGFPE
Reading that article while bored and revising for exams is not a good idea. My brain has switched off for the next few hours, which may impede my revision process. Although, there's probably a superstate in which I have both passed and failed my exams already, so does it really matter?
Can we get a "-1 Wrong" moderation option?
Extreme Programming for Quantum Computers:
I wonder if that will be the eventual effect of quantum computing. Think about it. Currently all sorts of things that happen in our lives and determin the course of history flow through computers. Votes, Communication, work schedules, Weather forcasts ect. ect. ect. This trend continues with computerss for the next 50 years at which time quantum computers are/become the norm. So at that point everything from the train arriving on time to if this comp-country goes to war is worked out on a computer. Then someone gets the bright idea to look outside of a window and finds the exact co-ordinates of a passing pigeon. Since all the Quantum computers are tied together by the Internet 3 all probability waveforms collapse and the future of the universe is set in stone from that point foward.
Before you flame yes I know that Quantum computing doesn't work like this. Still it is a good thoght experiment. Might make a good short story by an Author who may or may not be alive. (Dick perhaps ;)
Pithy, yet ultimately meaningless, phrase expressed with gusto!
Hell, even Einstein didn't buy it. He said, "God does not play dice with the universe."
Just because Einstein was brilliant doesn't mean he wasn't an idiot.
I've always get riled when people point to Einstein and say, "See, if Albert E. says it then it must be true."
Yes he made revolutionary contributions to Physics based on his ability to comprehend, categorize, and summarize work by previous Physicists in a way that even highschool students can understand, fundamentally. Relatvity permanently tweaked human cognitive faculties; he evolved human's thought process.
However, he still was a religious man, which is more psychological than scientific. I hardly think that refuting a promising, revolutionary discipline, such as QM, simply because of Einstein's deeply rooted fear of the unknown is absurd. We all know it's easier to solve problems in a petri dish than it is to solve problems in your personal life, that's why Albert E. abandoned his wife and kids for his first cousin! (And if I remember correctly, one son renounced him and the other went nuts. So is it OK to abuse your family if you're a genius?)
Even the smartest among us still try to put the religious blinders back on again. It's my job to call them on it. Sorry tb3, I'm not directing this at you, I'm just ranting.
-S
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https://www.accountkiller.com/removal-requested
A simplistic comment to be sure, but the article also touches on the clasic example of Schrödinger's cat: Certainly one of the more trotesque example of quantum mechanics, out there, but I guess the value is you'll never forget it. I guess that makes a difference
--
--Got Lists? | Top 95 Star Wars Line
> Einstein's concept of relative time and all this quantum religion
...and...
> are both offensive to anyone who has the guts to think by themselves.
> fundamentally abhorrent ideas such as quantum mechanical tunneling
> or particle-wave duality do not even deserve to be commented on.
Newtonian mechanics state that barrier tunneling is impossible as a phenomenon, and Maxwell's stuff doesn't touch on it. This idea developed from Einstein's GR theory. Understanding barrier tunneling allowed for the eventual discovery of materials that allow barrier tunneling in predictable ways. When these materials allow the tunneling specifically of electrons, they are labelled semiconductors. These materials can be made into computing machines that allow you to post a message to Slashdot saying that the theory that decribes their behavior is bunk.
There, now, don't you feel dumb?
There is little "common sense" in modern physics, but that's only because the sense you decribe as "common" is based on macroscopic observation, and these rules break down badly as you go to extremes of smallness, or bigness, or fastness, or farness. If you push two big magnet "North" poles together, they push apart, even when they're touching. Push two protons together, however, and after they get within a certain distance, they attract each other. Abhorrent? Perhaps. Impossible? Tell the residents of Hiroshima that it's impossible.
Virg
My bad. I was so into my response that I let that by. I hereby accept 5 swats with Schroedinger's Cat.
Virg
My .02,
My .02,
zencode
iactivist.org/jason
How about doing calculations on a quantum computer that doesn't actually have to be built?
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Technoli
Juno must be drooling over these quantum computers!
The White House said: White House spokesman Ari Fleischer was adamant Monday when asked whether the president would ask Americans to stop using so much energy.
"The president believes that it's an American way of life, that it should be the goal of policy-makers to protect the American way of life. The American way of life is a blessed one."
Wow. Let's see here...since Roe V. Wade abortion has also been an "American way of life," but I don't see him doing anything to protect it. Blessed my ass...
That just pisses me off when bone-headed leaders like Dubby can't figure out that change happens and that even "The American Way of Life" needs to change sometimes...
I've been using a similar method, alternately turning on and turning on my machine, to solve many daily tasks. For example, when I'm responding to a post-
"When I was young, we didn't have any o those sissy objects and icons. We had only zeroes and ones. My first assignment was a database management program, and I had to use only zeroes."
"You had zeroes? We had to use the letter 'O'."
Seriously speaking, how would the user know what was the problem he got the answer for? Maybe they would get 'segmentation fault, zeroes dumped' on every problem.
Just by meditating deeply enough, I should get Quake running on this mother any minute now!
sig sig sputnik
Thanks, now I have this even more surreal Blue Man Group thing stuck in my head. (They keep popping in and out of existence not in time to the beat.)
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www.lucernesys.comHorizon: Calendar-based personal finance
First, I'd like to point out that quantum computation and quantum encryption are two almost completely separate concepts. Quantum encryption is based on the fact that quantum states cannot be measured without altering. The most common example is the polarization of a photon, but it will work for any quantum state, so long as there exist, effectively, two unique states that can transmit the data.
Quantum computation, however, is much more complex and much more interesting. Quantum computers are based on the concept of quantum entanglement, the ability of a quantum state to exist in a superposition of all of its mutually exclusive states: It's a 1 and a 0. However, this is not as easy to use as one might think. While it's true that if you have n quantum logic gates you have the ability to input 2^n data values simultaneously (as opposed to only 1 piece of data if you have n digital logic gates), this is not going to be the end of classical computing for a few reasons. First, quantum computers have to be perfectly reversible. That means for every output there's an input and vice versa. And there has to be no way of knowing the initial states of the data. You don't process data, you process probabilities in a quantum computer; if you know exactly what any one value is throughout the computation, you can find out all of the values: the superposition ends and you're stuck with a useless chunk of machinery. This means YOU CAN ONLY GET ONE RESULT FROM ANY QUANTUM COMPUTATION, THE END RESULT. You can't see what the data in the middle is or the computer becomes useless. (Landauer's principle makes heat loss data loss. When your processor gets hot, it's losing data. If the same thing happened to a quantum computer, it wouldn't be quantum anymore.) Decoherence is what happens when you randomly lose data to the environment by design, not by choice, and the superposition ends. This is bad for Q.C. Oh, and quantum computers can only do *some* things faster, like prime factorization and discrete logarithms. Not multiplication or addition. Plus, the circuits that would do basic arithmetic would be bigger and slower than what you've currently got.
So what does this all mean? It means that quantum computers are going to provide some advantages (real quick big number factorization), and some disadvantages (that whole RSA standard). The most realistic initial use of quantum computers will be as add-ons to existing super-computers to resolve certain types of NP-Complete headaches that regular math can't simplify yet. At best they will someday be an add-on to your PC; but they will never replace the digital computer.~
If you want more info, check out http://www.qubit.org, it's got some decent tutorials.
Suppose you have a bomb with a trigger on its tip, so sensitive that a single photon hitting it will make it explode. Suppose further that you have some good bombs and some duds with stuck triggers that don't move. Can you tell which bombs are good and which aren't? Well sure, just hit it with a photon and see if it blows up. But can you do it without blowing up the bomb? Yes! (Well, probabilistically yes.)
Here's how it works: shoot a laser beam through a beamsplitter, bounce the two beams off of mirrors (one of which is attached to the trigger of a bomb) which redirect the beams back into another beamsplitter, with detectors on the other side. You won't understand the setup without looking at the picture -- I will be referring to it.
A laser beam is a coherent superposition of a bunch of photons. What happens if you turn the intensity down so much that you're getting single photons out? When the photon reaches the first beamsplitter, you might think that the photon either goes one way or the other. But quantum mechanics says that the photon enters a superposition state in which there is a 50% probability that it took the upper path and a 50% probability that took the lower path -- you won't know until you collapse the wavefunction by measuring which path it went through (by putting a detector along the path or something). (I'm being vague here: it's not that it went one way but you don't know until you measure it; rather, "which way it went" is simply undefined until you measure it, and if you don't measure it then it's never defined.)
So anyway, the photon hits the first beamsplitter and enters a superposition. If the bomb is a dud (fixed mirror), then this is an ordinary interferometer. At the second beamsplitter, the two beam wavefunctions (representing a single photon) interfere with themselves to produce a state with 100% probability of being detected at B and 0% probability of being detected at A. (You can see this from symmetry: the beam enters the system horizontally and has to come out horizontally too since the apparatus is symmetric.) This is precisely what you would expect classically with wave interference, by the way. Nothing too odd.
However, suppose that the bomb isn't a dud. Then the the impact of a photon on the mirror is free to move the trigger and set off the bomb, so the bomb serves as a measuring device! If it a photon hits it, the bomb will explode, so you have definitely measured that the photon took the lower path. What happens here? Like I said, there's a 50% probability that a measuring device (such as the bomb) inserted into the lower beam will measure a photon. If that happens, the bomb will explode. But what if the photon is measured to not take that path (by virtue of the bomb not exploding)? Then with 100% probability it took the upper path. When it hits the second beamsplitter, it's just as if it hit the first beamsplitter, since there's no interference from the other beam -- we know that nothing went that way. So with 50% probability it goes to detector A, and with 50% it goes to detector B.
The upshot: if the bomb is a dud, then you will get a photon at B with 100% probability. If the bomb is good, then you get an explosion with 50% probability, a photon at A with 25% probability, and a photon at B with 25% probability.
The point: if you get any photons at A, then you know for sure that the bomb was good. But you didn't actually ever send a photon to the bomb to find out! This is a "counterfactual" -- you are obtaining information about something that never happened (a photon hitting the bomb), but could have!!
Of course, you don't have an infallible scheme. Half the time you have a good bomb your test blows it up, and half the time it doesn't you can't tell whether it was good or not (because you got a photon at B). But 25% of the good bombs are provably good (without blowing them up). It turns out you can cascade this process to make the probability of detecting a good bomb as high as you want.
This effect is known as "quantum non-demolition" and has been experimentally verified (not with real bombs of course). You can use it to measure things using photons without destroying the photons (normally a photon is destroyed whenever it interacts with something -- it is absorbed).
I am intrigued/scadalized/cooled out by the article and (therefore) don't have the background to dispute it.
..or is this based on probability of some kind of tunneling right under the potential energy hill from start point to endpoint in a finite amount of time? (And is there such a "hill" in quantum computing, forgot to ask that too).
But what about:
-energy required to set up initial values so that the answer is all zeroes
-energy required for cooling or otherwise insulating/maintaining computer during the time it will be computing and simultaneously off
-who's going to police those qubits and tell them not to cannabilize energy from that environment (and presumably return it.. oops don't want to go there)
-would you need a reservoir of energy attached to the thing so that it would be theoretically possible for the system to go up the energy hump if calculation (in other universe required it)?
-do you ever even turn a quantum computer on anyway? seems a delicate enough computer could get by without humans intentionally putting power to it
-(back to the question of energy required to set up the computer): is there not a law which requires energy to create or change information, or is this a silly misconception. If so, are they not just taking care of energy expenditures before getting to the calculation stage, leaving a lot of the actual energy goings on in the unfathomable, unaccountable finite time span of computation? Or is there something else going on?
** It seems there is something more interesting going on, but there is neither mathematical meat for the professional nor a real explanation for the layman. The Royal Society Proceedings are too briefly abstracted to get anywhere. Could someone paraphrase or post the text of those proceedings or is this going to be an exercise in frustration?
In particular what exactly are the limits to the kind of probing you can accomplish which was mentioned in that abstract?
You are completely misunderstanding and need to read the original paper rather than the nature article. The strategy in the paper is not about saving energy. Quantum computers already use zero energy because they are reversible computers. The authors are not in the least bit confused about what they mean by off but it's not surprising you are confused because the Nature article is describing things in a stupid manner to be sensationalist.
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-- SIGFPE
"Michison and Jozsa describe a scheme for probing all the possible states of a quantum computer, including that in which all the 'switches' are 'off' -- that is, in which the computer is not turned on."
Just because your register is zeroed doesn't mean the chip is off.
I'll accept that the computer is off if it's not using any energy.
Cheerio,
Link.
True, but calculating this proof will definately need one of those computers!
It took a bit of head scratching and squinting, but I did finally manage to figure out how the thing works.
It uses some of the same theory as I would expect the "quantum computer" to use. In this case, they use a bomb which has a trigger which is sensative to a single photon of light. A dud bomb will pass the photon, but a live bomb will stop it. The experiment shows how it is possible to detect, using quantum mechanics, whether a bomb is live or a dud, without actually exposing it to the photon of light, and thereby exploding it.
I'm sure this is a much simplified version of what they're planning for the computer, but it's described in terms that pretty much anyone can understand, even though it's not obvious at first.
Help find a cure for Gidget.
I always tended to solve my Windows problems by just not turning the box on.
The White House said: White House spokesman Ari Fleischer was adamant Monday when asked whether the president would ask Americans to stop using so much energy.
"The president believes that it's an American way of life, that it should be the goal of policy-makers to protect the American way of life. The American way of life is a blessed one."
I say: Iron Monkey, what are you smoking? It's UNamerican to conserve. It is my patriotic duty to be an energy hog. Who needs these new-fangled 'putin machines work'in without 'tricity?
How I wish I had a quantum girlfriend that could take care of my problems without me having to turn her on.. no foreplay necessary...
Will they come with a sticker "Infinite Monkeys Inside"?
And if you watch the screen while it's running, will this collapse the computer's state and break it?
One line blog. I hear that they're called Twitters now.
Does this machine run on software that doesn't have to be written?
Problem solved.
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Friends don't let friends use multiple inheritance.
I swear, anything that is published through Nature has to be the most questionable of all things. Unfortunately, this argument is missing the most important part of quantum computing, the collapsing of the states into the final results. Without that you end up with unknown states, which you can guess the probabilities for all the possible outcomes, which in the end makes you do the whole thing by hand anyway. Trust me, I've got plenty of quantum particles making up my body and I am the master and doing a whole lotta nothing. By their logic, I should not have failed differential equations.
Why, of course, it should be well-known that while nobody looks at a quantum computer, it can be on, off, or both, right?