Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: samiam on March 10, 2012, 08:48:58 pm
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BM scientists said Tuesday that they have made several breakthroughs in quantum computing that put them "on the cusp of building systems that will take computing to a whole new level."
The IBM researchers said they have established three new records "for retaining the integrity of quantum mechanical properties in quantum bits, or qubits, and reducing errors in elementary computations." Those advances, presented at this week's annual American Physical Society meeting, get the team "close to the minimum requirements for a full-scale quantum computing system as determined by the world-wide research community."
nerdgasm
"The special properties of qubits will allow quantum computers to work on millions of computations at once, while desktop PCs can typically handle minimal simultaneous computations," the IBM researchers said. "For example, a single 250-qubit state contains more bits of information than there are atoms in the universe.
"These properties will have wide-spread implications foremost for the field of data encryption and other possible applications such as searching databases of unstructured information, performing a range of optimization tasks and solving previously unsolvable mathematical problems," the team added, further elaborating on the possibilities of quantum computing in the video below.
Enjoy being unable to secure your passwords by this time next year! Also Skynet.
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Wait, I could have sworn that IBM or someone was already selling quantum computers, as in they already had some ready to go, or nearly ready at least. I guess they were farther off than I thought. Maybe they were just looking for potential customers. Ah well, cool stuff either way. FSO 3.7 is going to support quantum CPUs right?
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Wait, I could have sworn that IBM or someone was already selling quantum computers, as in they already had some ready to go, or nearly ready at least. I guess they were farther off than I thought. Maybe they were just looking for potential customers. Ah well, cool stuff either way. FSO 3.7 is going to support quantum CPUs right?
I suspect you're probably thinking about quantum encryption.
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Nah, I'm pretty sure it was honest-to-god quantum computing they were talking about. I bet I just misread the story or something. Maybe they're taking preorders... :nervous:
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I just realized that this will probably result in machines smarter than us.
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These will be the last computers designed by humans. :eek2:
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I for one welcome our new robot overlords!
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just set the computer's goal on enhancing human cognitive abilities, rather than on making better computers and we will be the new robot overlords.
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First they make a 155GHz CPU.
Then they can fit one bit on 12 atoms for an HDD.
Now Quantum Computing.
IBM has some cool ****.
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this is all well and good, but until i can play crysis on one i don't care.
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Can someone explain to me what is a quantum computer?
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It's a computer with really tiny bits that uses quantum physics to compute exponentially faster with each additional bit you throw in.
You can read the article, where it explains it, or just think of it as a really, really fast computer from Star Trek or The Matrix.
What surprises me is how they're coming out with this about 20 years earlier than I thought they would.
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Quantum computers are very interesting because (at least from the theory I know) they are absolutely incredible at some forms of computation that digital computers are awful at, and absolutely awful at some forms of computation that digital computers are good at.
I may be completely wrong though
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Isn't the problem with quantum computers that observing the results alters the result?
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Isn't the problem with quantum computers that observing the results alters the result?
No.
e: I should clarify. Handling quantum decoherence is a huge problem in designing quantum computers, yes. But it's very easy to be misled by popular discussion of quantum physics.
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Quantum computers are very interesting because (at least from the theory I know) they are absolutely incredible at some forms of computation that digital computers are awful at, and absolutely awful at some forms of computation that digital computers are good at.
I may be completely wrong though
No they're good at everything. They're just really hard to make.
Where's Hera?
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No they're good at everything. They're just really hard to make.
Where's Hera?
Herra is an enthusiastic amateur about many things, and while the enthusiasm is laudable, you should always keep in mind the amateur.
I'm not great at this domain of computational physics but I've reached out to someone who is. Moment.
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No they're good at everything. They're just really hard to make.
Here's the verdict as I understand it: while yes, in theory, a universal quantum computer can do anything a universal classical computer can do, assuming Turing-style infinite memory, in practice decoherence protection becomes escalatingly difficult as the number of qbits in the quantum computer scales. Even with optical lattices, topological computing, what have you, this is still an issue. (IBM has doubtless made enormous strides in this field if they're claiming en-cuspedness.)
By contrast, classical computers can be built with an essentially arbitrary number of bits and the cost doesn't scale too sharply (linear or log function, I believe).
In practice what's likely to happen in the near future is that quantum systems will serve as specialized processors, loosely analogous to GPUs, that target specific operations. (When one of those operations is something like Shor's algorithm this is still a huge deal.)
Again, though, I am prepared to be totally wrong.
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Isn't the problem with quantum computers that observing the results alters the result?
back in the olden days of computing when they used core memory, simply reading the data destroyed the data, so after reading a bit of data you would have to re-write it. they actually designed the computer architecture around these limits, it also altered the programming paradigm. you would do a lot of inline operations, read a var, do computations on it and then store it back into memory at the same location. if you needed to free up some ram, just read a bunch of vars you werent using anymore.
core memory is awesome though because it was not volatile. you could power it off at the end of the work day and come back next morning and resume where you left off without having to load any punch cards. the **** was durable as **** too. some core memory recovered from the space shuttle challenger (it was used because of its immunity to radiation) was still in tact and readable, they were able to do a core dump and analyze the data. yes the phrase core dump comes from the core memory days. nothing to do with quantum computing but its cool ****.
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It's good that you're ready to embarrass yourself, I am too. They are hard to build, because of decoherence as you mentioned. They also are more suited to parallel processing than sequential processing, which is what I think you're getting at. Quantum computers solve BQP problems efficiently while classical computers solve BPP problems efficiently, if you want to sound smart.
Quantum computers use the phenomenon of quantum entanglement. It's possible to entangle two quantum particles so that certain states on one particle (or qubit), such as spin, affect the state of the other qubit.
You know how logic gates work, right? The NOT SEXP and the AND SEXP? Well let's say two qubits are entangled so that qubit A always has the opposite spin of qubit B. So if qubit B is manipulated to have an up spin, A will have a down spin. We've just made a NOT logic gate.
Now say that qubit C is entangled with both in such a way that it will only display an up spin if both D and E display an up spin. That's an AND logic gate. And so on, recreating the entire series of logic gates that exist in any other processor.
The great thing about quantum computing is that each qubit may be entangled with every other qubit in the processor at the same time, so you can perform exponentially greater operations if you can increase the number of qubits entangled with each other. Basically, infinite money. Exponential versus linear. Although everything's log, really, if you take it far enough.
However, if you were to write a program for the quantum computer, it would have to wait for each gate to complete its current operation before proceeding to the next step. So one should always try to construct the problem in a way that allows parallel processing to get the most juice out of each step when writing code for these machines. But the high speed of data transmission between qubits (near instantaneous) and the exponentially increasing parallel capabilities with each additional qubit makes these computers a whole lot more effective than classical computers for most problems if the programmer isn't an idiot.
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It's a computer with really tiny bits that uses quantum physics to compute exponentially faster with each additional bit you throw in.
You can read the article, where it explains it, or just think of it as a really, really fast computer from Star Trek or The Matrix.
What surprises me is how they're coming out with this about 20 years earlier than I thought they would.
I read the article but didnt understand that well, thanks for the info.
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e: nm
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i always figured quantum entanglement would have communications applications rather than computing applications. using it for say instantaneous communication over astronomical distances, such as real time command and control of mars rovers and the like. but im not sure i understand the quantum mechanics well enough to say if thats feasible or not, though i do know under traditional physics this would be impossible.
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That'd actually be a different technology. Recently, there was an experiment conducted that seemed to prove FTL communication via quantum entanglement possible.
Quantum computers might be able to solve some really interesting mathematical problems, aside from being really useful everywhere you need a really fast computer.
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i always figured quantum entanglement would have communications applications rather than computing applications. using it for say instantaneous communication over astronomical distances, such as real time command and control of mars rovers and the like. but im not sure i understand the quantum mechanics well enough to say if thats feasible or not, though i do know under traditional physics this would be impossible.
As of the present understanding of quantum physics, this is completely impossible. Quantum entanglement cannot pass information without a classical (and thus subluminal) channel as part of the system.
That'd actually be a different technology. Recently, there was an experiment conducted that seemed to prove FTL communication via quantum entanglement possible.
This did not happen.
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That'd actually be a different technology. Recently, there was an experiment conducted that seemed to prove FTL communication via quantum entanglement possible.
This did not happen.
IIRC, there was a recent experiment (posted on these forums, no less) where a sub-atomic particle was split, and then manipulated. What happened to one part of the divided particle seemed to happen to the other.
No idea if it was "real", though.
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As of the present understanding of quantum physics, this is completely impossible. Quantum entanglement cannot pass information without a classical (and thus subluminal) channel as part of the system.
could you elaborate on this? I've never quite understood how quantum entanglement worked. all explanations I've read have had a "and stuff happens" part in it.
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That'd actually be a different technology. Recently, there was an experiment conducted that seemed to prove FTL communication via quantum entanglement possible.
This did not happen.
IIRC, there was a recent experiment (posted on these forums, no less) where a sub-atomic particle was split, and then manipulated. What happened to one part of the divided particle seemed to happen to the other.
No idea if it was "real", though.
This is completely believable - the problem is that this, on its own, isn't useful for communication. If the end state is randomly determined, for instance, you need a classical channel between the two endpoints to actually use it for anything.
Quantum entanglement will be most useful for computation and encryption, not communication.
could you elaborate on this? I've never quite understood how quantum entanglement worked. all explanations I've read have had a "and stuff happens" part in it.
Oh, boy. A good and fair question. Let me give it a shot.
Let's say we entangle two particles. What does this mean? Well, they've both been generated from the same source, for instance, and we know that (because of the laws of the source process, maybe a particular kind of decay), one particle must have an UP spin, and the other a spin of DOWN.
Now, here's the thing: we haven't actually measured the particles yet, so we don't know which one spins UP and which one spins DOWN. In ordinary, classical physics you might think, 'well, one's UP, and one's DOWN, and we just have to look to find out. It's like checking a snake's gender: you don't know until you look, but it's always been a male or a female.'
But in quantum mechanics -- due to the results of a lot of experiments and math -- we've come to believe that both particles actually exist in a state of quantum fuzziness, both UP and DOWN simultaneously. This state of fuzziness lasts until we measure them. When we measure one particle, we collapse the quantum waveform and find out that - wow! this particle spins UP.
It's important to note that the chances of getting UP or DOWN are 50/50. It's a random outcome, a coin flip.
And from there we know that the other particle spins DOWN. It has to; spin has to be conserved.
But hang on a second. If that other particle was in a state of quantum fuzziness, and we still haven't measured it, why did its waveform collapse to DOWN? These particles aren't connected - they might even be hundreds of miles apart. Surely the other particle is still in a state of fuzz, UP/DOWN, waiting to be measured.
But no. It's definitely DOWN. We can check this experimentally. It'll always turn out to be DOWN...as if it somehow knows the other particle turned out UP. It's as if you flip a coin in one room, and every time it comes up heads, a coin flipped in another room comes up tails -- even though there's no communication between the two.
But if there's no hidden variable to be measured, how does this particle know what its distant sibling turned out to be? How does the coin know how the other coin landed?
There has to be some kind of spooky action at a distance - some sort of instantaneous, nonlocal link between the entangled particles that lasts until they're measured.
That's a really simplified explanation. I can go into more detail if you like, and also try to explain why it's completely useless for communication, but good for encryption.
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That'd actually be a different technology. Recently, there was an experiment conducted that seemed to prove FTL communication via quantum entanglement possible.
Quantum computers might be able to solve some really interesting mathematical problems, aside from being really useful everywhere you need a really fast computer.
I.e. Gaming :) Just admit it, we re all thinking it! ... best chance of developing AI that will take over the world as well!
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I can ... try to explain why it's completely useless for communication
Please. That's the part that I don't quite get.
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I can ... try to explain why it's completely useless for communication
Please. That's the part that I don't quite get.
Simply put: when you measure the particle's spin, the outcome is completely random, so there's no way to exchange meaningful information.
Say you decide to measure your entangled particle and you get UP.
Meanwhile, the other guys, on Alpha Centauri, measure their entangled particle and get DOWN. They suspect that maybe this is because you measured yours and got UP...but, some of them suggest, it's really just a random measurement, and you on Earth haven't made the measurement at all yet.
What does that tell either of you? Nothing. There's no way to distinguish decoherence-as-a-signal from the simple random outcome of measuring the particle.
The only way to use an entangled pair for useful communication is if you also have a classical channel, a way to tell each other what you're doing...which is, of course, slower than light.
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ok, I thought there was some way you could change a property of an entangled particle and that change would manifest in the other.
this does feel like there is something here though, either the fuzzyness isn't as fuzzy as we thought of some sort of ftl thing is happening, probably the former :\
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I hereby declare that the simile "like checking a snake's gender" needs to be used far more often than it is.
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ok, I thought there was some way you could change a property of an entangled particle and that change would manifest in the other.
this does feel like there is something here though, either the fuzzyness isn't as fuzzy as we thought of some sort of ftl thing is happening, probably the former :\
You can change a property of an entangled particle and the change manifests in the other - the problem is that you can't decide whether to set the particle to UP or DOWN; the outcome is random.
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Well damn. I thought we could control that somehow. And even if you could you wouldn't know for sure if the other guy had his particle "set" or not.
No ansibles then. :doubt:
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You can change a property of an entangled particle and the change manifests in the other - the problem is that you can't decide whether to set the particle to UP or DOWN; the outcome is random.
but you can chose to change it or not right? what if you set up a system where it changes some property a 50 times every microsecond for a one and not at all for a 0, the other side writes a 1 if any change happened within a time window, and 0 if no change was observed, wouldn't that be usable? sure with that particular setup you would be likely to have an erroneous bit every petabyte or so, but CRC can correct for that.
or are there natural flips like this that also happen and there would be no way to tell if it was you compatriot on the other end or just random quantum noise?
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I think the point is, if you measure a change on the other side, you have no way of knowing if it was intentional or not.
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(Gah, ninja'd.)
The trick with the quantum world is that the particle doesn't "collapse" into one set possibility, and therefore set the other entangled particle the opposite way, until you actually perform the act of measuring it. (Crazy? Yes, but that's quantum for you.) Battuta's point is that, from the perspective of the person on the other end getting your "signal," there's no way to tell if the result they're seeing is due to your initial collapse of the first particle's waveform, or their collapse of the second in the process of measuring it. And on top of that, the person sending the "message" has no control over what state the first particle collapses into...like Battuta said, it's just like flipping a coin. To further that analogy, the entire process is akin to the sender not even knowing what message they're going to send until after they flip a coin, and the receiver having no way of knowing if they're getting the results of the first coin flip, or instead flipping their own coin. The only way to make it work would be for the sender to also send a message stating what their initial result was...which kind of defeats the whole purpose, since that message could only travel at the speed of light anyway.
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but you can chose to change it or not right? what if you set up a system where it changes some property a 50 times every microsecond for a one and not at all for a 0
Once the particle has been measured, the entanglement snaps. (uh i'm pretty sure at least) You get one use of each particle, that's it. Not that the use buys you anything, because...
the other side writes a 1 if any change happened within a time window, and 0 if no change was observed, wouldn't that be usable?
How do you know if anything changes? You have to measure the particle to check its value, which causes its quantum state to collapse to UP or DOWN.
Say you measure the particle and get spin UP. How do you discern between the following scenarios:
1) The other side hasn't taken a measurement yet. You just did the first measurement and got spin UP.
2) The other side has taken a measurement and got spin DOWN.
I was about to make another coin flip analogy but Mongoose did it better.
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Basically the whole uncertainty thing is a theoretical construct and you could just as accurately say that no data transmission ever took place and the spin of each particle was predetermined. I know, sometimes interpretations of quantum physics are unnecessarily confusing.
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Basically the whole uncertainty thing is a theoretical construct and you could just as accurately say that no data transmission ever took place and the spin of each particle was predetermined. I know, sometimes interpretations of quantum physics are unnecessarily confusing.
This is a problematic statement. One argument (the hidden variables interpretation) claims this, but there's some experimental evidence that there are actually no hidden variables and that the spins really are in a state of quantum superposition until the moment of measurement.
You're trying to simplify quantum mechanics to a classical approximation - believe me, we'd all like to. But unfortunately that hasn't been viable for several decades.
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How would quantum entanglement help with communication, even if you had another communication channel then?
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How would quantum entanglement help with communication, even if you had another communication channel then?
Here's some reading related to cryptography:
http://en.wikipedia.org/wiki/Quantum_cryptography
http://en.wikipedia.org/wiki/Quantum_key_distribution
These rely on the combination of quantum entanglement with a classical channel.
I don't feel confident enough about my quantum kung fu to speak to more elaborate applications.
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Quantum entangle-o-gragy communication works all the time in Mass Effect 2, I don't see the problem.
This is a problematic statement. One argument (the hidden variables interpretation) claims this, but there's some experimental evidence that there are actually no hidden variables and that the spins really are in a state of quantum superposition until the moment of measurement.
That's not an argument, it's an interpretation. It's a simpler and more GD-worthy interpretation than the cat state.
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you should probibly look at the way traditional wireless communication works. anything in the radio spectrum needs a carrier wave which is modulated with the information you want to send. at the other end you look for a frequency that is close to to the desired carrier wave, and when you have locked on to that wave form you can then subtract the carrier from it and retrieve the information (there are different modulations you can use for analog or digital data). in addition, when dealing with digital information you also need to have a protocol for identifying and retrieving frames. when the vaue can either be 0 or 1, you dont have a unique value for when a frame starts. usually a transition from the idle state followed by a bit pattern denote the start of a frame, then comes data, and some form of error checking (to both detect errors and to confirm that what was received was in fact a frame). optical systems probably work slightly different, but im not going into that, but you still need a protocol to make sure that what you're getting is data.
for entanglement to work as a means of communication you would need to be able to predictably control a particle's state. which according to the posts in this thread is not how entanglement works. for it to work at the other end you would need to see the state of the particle at all times, which again is impossible. you need to see everything, even the noise, to lock onto a data frame.
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But if the entanglement "snaps" when you measure it, won't that make it useless except as a random number generator that two parties can secretly share?
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I guess it would, and I have no idea where Bioware came up with the idea of quantum communication.
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You can change a property of an entangled particle and the change manifests in the other
ok, I must have misunderstood you right here, what I originally meant (and you were responding to here) was that you can change the property of a particle, after both sides had measured it, and then when measured again both particles would have maintained their relationship
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Quantum entangle-o-gragy communication works all the time in Mass Effect 2, I don't see the problem.
This is a problematic statement. One argument (the hidden variables interpretation) claims this, but there's some experimental evidence that there are actually no hidden variables and that the spins really are in a state of quantum superposition until the moment of measurement.
That's not an argument, it's an interpretation. It's a simpler and more GD-worthy interpretation than the cat state.
It's an interpretation that has at least some experimental evidence stacked against it, and it may (I'm not up on my quantum) have been ruled out entirely by the Bell experiments.
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Extensions of QEM both with and without hidden variables provide the same accuracy of prediction, although I'm not quite sure what that means.
In any case a Bell test involves using polarizers to force a certain state, not merely observing a quibit, so it's not quite the same process. Observing a quibit is still going to produce results consistent with nonlocal hidden variables.
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The Bell theorem rules out all local hidden variable theories, though not nonlocal ones.
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Whoop, I just edited my post.
Bohm theory agrees perfectly with nondeterministic quantum mechanics. It's a more parsimonious explanation for superposition, unless the discussion keeps going on and gets into many worlds or pilot waves.
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Enjoy being unable to secure your passwords by this time next year! Also Skynet.
No matter how often I read it Samiam,... that one liner you wrote there still cracks me up! Also Skynet.
lol.
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I guess it would, and I have no idea where Bioware came up with the idea of quantum communication.
Probably in the same place George Lucas came up with light sabers.
Thought experiment:
Let's say there are 16 coins, all entangled in pairs. The sender has 8 and the receiver has the rest. They are on the opposite sides of the known universe.
The sender tosses 7 of them, while the number 8 one is measured by the receiver.
The sender checks whether he has heads or tails on the 7 coins he flipped. He then tosses the coins that have a tail but need to have a heads and vice versa, until he gets the right combination.
The receiver keeps on measuring the 8th coin, only to find out it's still laying on the same side.
When the sender's coins are flipped so that they represent the information to be sent, he measures the 8th coin and flips it until he gets the opposite side.
The receiver then finds the 8th coin changed sides and reads the other 7, does a NOT operation to each one and gets the message.
Now since quantum comms are impossible, where is the flaw in this thought experiment?
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The very act of measuring a coin flips it. So the chance that you're receiving a message or a random observation is 50/50.
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Well then, the receiver measures the number 8 coin and gets:
H->T->H->T->T; and the double tails means it was flipped on the other side, time to receive the message.
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You can't measure a particle OR impose a state without severing the link.
Otherwise it wouldn't be any more difficult than transmitting information over the (STL) wire.
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Thought experiment:
Let's say there are 16 coins, all entangled in pairs. The sender has 8 and the receiver has the rest. They are on the opposite sides of the known universe.
The sender tosses 7 of them, while the number 8 one is measured by the receiver.
The sender checks whether he has heads or tails on the 7 coins he flipped. He then tosses the coins that have a tail but need to have a heads and vice versa, until he gets the right combination.
The receiver keeps on measuring the 8th coin, only to find out it's still laying on the same side.
When the sender's coins are flipped so that they represent the information to be sent, he measures the 8th coin and flips it until he gets the opposite side.
The receiver then finds the 8th coin changed sides and reads the other 7, does a NOT operation to each one and gets the message.
Now since quantum comms are impossible, where is the flaw in this thought experiment?[/color]
This doesn't work on two levels.
1) You cannot assign a coin a value. It comes up randomly heads or tails when you look at it. You cannot flip the coin more than once; once you look at it, it's either heads or tails, now and forever.
2) As stated quite clearly earlier in the thread, it is impossible to tell whether the other side has already examined the coin when you look at it. There's no way to distinguish 'this coin has never been examined, and I've just examined it' from 'the other side has examined this coin, and I'm seeing the opposite of what they're seeing'.
Think of it this way: you're given 8 coins in a box with a closed lid. You're told that either someone flipped all the coins and then put them in the box as they fell, or the coins have all been flipped randomly inside the box after it was closed. You're told that you have to determine which, or they'll kick your dog.
How do you stop your dog from being kicked? You can't. Either way the coins were flipped randomly.
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H->T->H->T->T; and the double tails means it was flipped on the other side
No it doesn't. Each measurement has a 50/50 chance of being spin UP or DOWN. Observing the particle doesn't guarantee the spin will flip anymore than flipping a coin guarantees you'll go from H->T or vice versa.
To reiterate Battuta, this means there is no way of knowing if the observed spin of your particle is a result of your measurement, or due to the entanglement effects from the other side making their measurement, without a carrier signal, which is not FTL.
Also, what Ghostavo said.
edit: And what Battuta ninja'd with. D:
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Assuming that it was possible to violate the Bell Inequality and create particles with identical spin, I wonder how badly that would screw physics up. Would you get a perpetual magnet motion milkshake or something?
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Assuming that the laws of physics could be broken, how broken would the laws of physics be?
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Assuming that it was possible to violate the Bell Inequality and create particles with identical spin, I wonder how badly that would screw physics up. Would you get a perpetual magnet motion milkshake or something?
*This universe has encountered a fatal exception in §!""!###")=()!##+&§(/!"§42!""##!)("*
*Please contact customer support if the error persist uppon rebigbootbanging*
Never divide through zero... and if your data inputs aren't secured, this will happen too: http://xkcd.com/327/
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(http://imgs.xkcd.com/comics/exploits_of_a_mom.png)
That's a good 'un. About wraps up the thread.