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Baby Steps Toward Quantum Computers
Mz6 writes "In a step toward making ultra-powerful computers, scientists have transferred physical characteristics between atoms by using a phenomenon called entanglement, which Einstein derided as 'spooky action at a distance' before experiments showed it was real. Such 'quantum teleportation' of characteristics had been demonstrated before between beams of light. Teleportation between atoms could someday lie at the heart of powerful quantum computers, which are probably at least a decade away from development. Researchers using lab techniques can create a weird relationship between pairs of tiny particles. After that, the fate of one particle instantly affects the other; if one particle is made to take on a certain set of properties, the other immediately takes on identical or opposite properties, no matter how far away it is and without any apparent physical connection to the first particle." Reader starannihilator adds: "Physics Web provides a good graphic summary of the phenomenon, as well as a good technical article."
I think (although I'm not certain) I read somewhere that a quantum computer is like an analogue computer - where you're not restricted by 0 and 1. Is that correct?
Just say 20 years from now I am on my quantum fandangle computer that does sub-atomic calculations, what happens when background radiation hits the processor and flips a few 1s and 0s?
i.e. will my computer crash when there is a solar flare?
will the new "heatsinks" be lead shields?
will we need to rotate the shield harmonics? (j/k)
please... inquiring minds want to know.
This wiki looks good, and if it isn't too technical, maybe I can find the answer. However, every other article, paper, or discussion that I have seen skips this one question of mine: How is the choice made between all the superimpositions to select ther 'right' answer? Everyone goes to great lengths to explain the superimposition part and its implications for massively parallel computation, but no one ever says how you choose the result! Does anyone have a clue about this?
Rome wasn't bilked in a day.
Sounds more like the basis for instantanious comunication (read too much OSC). If we ever invented non reltivistic FTL or spread far enough that we'd need instantanious communication it would probably be based on this.
"Sic Semper Tyrannosaurus Rex."
Can someone explain why this can't be used for FTL communication? The folks at Cornell seem pretty convinced that FTL communication is impossible, but from my reading of the article, in this experiment the first particle is forced into a known state, so (IANANuclearPhysicist but) it seems to me that if the state of the second particle can be measured (even if that measurement causes the state to change), communication has been accomplished. What am I missing?
I am not a physicist, or a physics student, or even an arm chair physicist, but from what I understand, creating a quantum gate requires (at least?) 3 particle entanglement, which is quite a bit more difficult than 2 particle enganglement. Can anyone better versed in the subject confirm or refute this?
Famous Last Words: "hmm...wikipedia says it's edible"
We hope to be able to use this for computing, but we know it could be used for communication even better. All we have to do is develop better, cheaper tools for manipulating & reading the particals.
Unfortunatly, so far it only seems to work with pairs, we can't seem to get multiples going, so use is limited. but let's try this from the military point of view: In theory, we could build 'ansibles' (to steal from Orson Scott Card) that operate in pairs. Every ship and command unit could have one, the other one would be connected to a complex of normal computers that woudl determine which other ansibles to send the message to.
No static or bad connections, and no need for encryption as there is no way to intercept the communications!
"It takes a very long time to count to 2 in binary." ~'Fourlegged'
Is the idea here basically just that this means that they'll be able to transmit information between qubits without the qubits having to be right next to each other?
Does this mean they might finally break that 7-qubit barrier that quantum computers up until this point had seemed to have been limited to?
I really don't get exactly what's going on. I ASSUME the news doesn't mean that they've find a way to transmit information instantaneously using QE.
Irritable, left-wing and possibly humorous bumper stickers and t-shirts
If it is FTL communication, then we've stumbled into the area of electrogravity.
FTL is not an impossibility; it just stands in relation to relativistic physics as it stands in relation to classic physics.
As many know, around a black hole there is a very strong gravitational field. This field has the property of bending the dimension of time itself. We can therefore state that time is not linear, and that a hypothetical theory of electrogravity would be entirely four-dimensional. This would mean that as far as the theory is concerned, there is no difference between cause and effect (as you can from our 3D perspective look at it backwards and forwards; wine filling a shattered glass that reassembles and hops up on the table), and time would be something that only stood in relation to us. The actual EG math, formulas et al., would be like the math familiar from school. - No time variable. - The formulas simply show how things stand in relation to each other, and if one thing is the cause or the other is effect; that is entirely up to us to determine.
All rites reversed 2010
Okay, so this is probably incorrect, but it is a train of thought. With the state of quantum encryption being that if a third party observes the key in transit, it is apparent, and the key is useless, would this have a potential application to break this encryption.
Using this method, the duplicated particles could be observed, leaving the original particles in the encryption stream relatively unmolested. Yes, it would be impractical and the equipment needed would be very distinctive and difficult to hide, but it raises the possibility.
InfoSec that matters, when it counts.
IANAP, and in the high level articles I've read, I've never seen spin discussed to anymore depth beyond just that it's a property of fundamental particles. I know that force particles have integer spin (and thus ignore the exclusion principal), and matter particles have half integer spin (and have to obey the exclusion principal), but I don't know what that means physically, or how you measure it. Does it have to do with angular momentum? From a macro world of physics, to measure the angular momentum of something, you can apply a torque and see how quickly it accelerates. I also know that you can measure the charge and mass of a particle by seeing what sort of spiral it makes in a cloud chamber. Is measuring spin related to either of these techniques at all? Thanks for the help!
Komi
The ultimate goal of science is to unify all forces of nature to a single law that can be silk-screened onto a T-shirt.
"Researchers using lab techniques can create a weird relationship between pairs of tiny particles. After that, the fate of one particle instantly affects the other; if one particle is made to take on a certain set of properties, the other immediately takes on identical or opposite properties, no matter how far away it is and without any apparent physical connection to the first particle." ---- Can it always be told beforehand (whether true for all cases) if the other will take identical or opposite properties? Is is controllable/determinable by us what properties the other will take? If A&B entangled and later C entangles with either of them, will it be considered that all three are entangled with each other? and if any property of A changes it will cause some change in properties of B and C to maintain the harmony b/w A,B&C to a state that was? (ought to be?) before the property of A changed? On the wondering scifi side, does all the discussion here, seem to point that parallel universes are possible?? One of the Futurama episodes deals with lots of weird parallel universe stuff (entire universe in a box stuff).
Well, actually I don't, but that's another matter.
However, it seems that every time somebody mentions something about 'quantum' people around here go into Batman and Star Trek Mode.
1. This whole thing is still very much in the early days of fundamental research. Think Babbage or Archimedes or something similar. I suspect that much of the hype about 'quantum computing' is simply a magical mantra that produces funding.
2. There still is no such thing as teleportation, not even theoretically. Entaglement only means that you can get two objects to behave 'in step' even at a distance, but so far it has always involved that they start out together, ie. physically close to each other. Teleportation on the other hand is normally thought of as transporting mass from one point of space to another, sort of magically, without passing through the space and time that seperate the two points. There really isn't much chance of that ever making even theoretical sense.
Others said that measurement of an entangled particle will make it loose its state (collapse of superposition), but how are we going to get information out of the quantum computer ? can we use the same way to successfully read the quantum state for communication ?
After all, transmission of information in a computer circuit is no different than communication.
I was trying to think in everyday terms why quantum entanglement seems so strange and came up with this. I am not sure if this is accurate so correct me if I am wrong.
It would be like I had two coins that I could flip. Two classical coins could come up as both heads, both tails or one head and the other tails. Normal statistical behavior.
An entangled version of these coins when I flipped them would always come up either both heads or both tails for example. (It could also always be if one is heads, the other must be tails as well)
If this happened with classical coins we would say that something about the coins or environment was rigged. This is what Einstein thought.
However with quantum entangled coins this would be perfectly acceptable behavior.
No. Once you've measured them, the entanglement is destroyed. Actually, it's not quite right to say you change the state of the one or the other particle, because in an entangled state, the entangled particles do not have a defined state on their own. They only have a joint state, the entangled state. Now measuring them causes that state to "collapse" into one where the particles have a well defined state. However, which state they have is mostly random. The only thing which is fixed is (a) that this state corresponds to whatever you've measured (e.g. if you measured the z-Spin, you'll get a state with defined z-Spin, while if you measured the x-Spin, you'll get a state with defined x-Spin instead), and (b) that the other particle will be in a state which is determined by both the original entangled state and the state the measured particle has after your measurement, even if at the time of the measurement the other particle is lightyears away and has no physical interaction with the measured particle or the measuring device.
So basically, you cannot really change the state of a far-away particle, but you can force a far-away particle which had no well-defined state into one that has, if you have the particle it is entangled with.
Should be clear by now: You can detangle them by measuring them.
You have three entangled particles.
Well, that's the complicated one. Does this help you?
The Tao of math: The numbers you can count are not the real numbers.