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What's the link between quantum computing and stopping light?

F

Fox2k

Member
First of all I'd like to say I'm not sure if this is posted in the right forum, if not, please move it. 🙂


I've been looking into the topic of stopping light, and have read about how two teams of harvard university have succeeded in suspending a beam of light in a cloud of atoms, thus bringing it to a "stop" in a sense, and being able to hold it for just under a millisecond. I've printed about a dozen articles on this matter, and each article relates this to the theory of quantum computing, with "qubits", able to represent states of both one and zero at the same time, exponentially increasing the processing power of modern computers. I'd like to ask of anyone familiar with these subjects, to draw a link for me.

I understand that qubits involve the spin state of electrons, and I have a grasp of the basic concept. What I don't understand is how this relates to controlling the speed of light and bringing it to a stop. Every article I've read ends with something along the lines of "this advance brings up possibilities such as that of quantum computing..." without explaining how the two are connected.

 
if you can stop light, you now have an optical switch. light coming through = 1 no light ( or light stopped ) = 0.

Build enough of them and you now have a optical CPU that is way past everything we have now in terms of speed.
 
but this is back to binary; a linear progression of information. you can't have a sensor say "there is light", "ther is no light", or "there sort of is light"

 
Originally posted by: Fox2k
but this is back to binary; a linear progression of information. you can't have a sensor say "there is light", "ther is no light", or "there sort of is light"
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I don't understand what you're saying. If you can stop/block one beam of light using another, you have for all practical purposes an optical transistor. From there you can build an optical processor.

Voltages/currents in processors are not "there is current" and "there is no current", but instead "there is a lot of current" and "there is very little current". When you get to the really low levels, 1 and 0 aren't as distint as you might think.
 
Originally posted by: CTho9305
Originally posted by: Fox2k
but this is back to binary; a linear progression of information. you can't have a sensor say "there is light", "ther is no light", or "there sort of is light"
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I don't understand what you're saying. If you can stop/block one beam of light using another, you have for all practical purposes an optical transistor. From there you can build an optical processor.

Voltages/currents in processors are not "there is current" and "there is no current", but instead "there is a lot of current" and "there is very little current". When you get to the really low levels, 1 and 0 aren't as distint as you might think.
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lol, i'm trying to explain quantum optical physics with a 12th grade education
😀

i'll see if I can make my confusion clearer:
quantum mechanics deal with the possibility of qubits representing both on and off (1 and 0) atthe same time. I don't see where this subject comes into play with stopping light. I can see where information moving at light speed would obviously make computer faster, but where does quantum computing come into play in all this?
I just dont see the connection, but obviously there is one since every article mentions both topics together
 
I have read about the possibility of being able to change the spin of particles in quantom computers, but also a theory of being able to see what the spin was at a certain point in time. IE: The spin of particle A is A1 at time X, Then at time X1 the spin of A is A2. And by being able to access what the spin was at X, X1 ect, you could theoretically have infinite storage since time continues to occur...
In case you did not know, the spin of the particle is used to represnet 1s, 0s, and possibly going beyond a binary system in that the spin can go more than 2 directions I believe? Thus processing power is quite amazing and storage being infinite..well. and since physics supposedly allows some form of time travel (reverse) this could allow you to access what the spin was at a given time.
Well I don't know a whole lot on the topic but it's very interesting.
 
Quantum computing is an interesting field. I'm not sure what the connection is relating to the ability to stop light, but a qubit is something like a regular bit. It has that same properties of being spin up or spin down, 1 or 0 just like a transistor. The power of using qubits comes in however when you think about it in a quantum mechanical sense. In quantum mechanics everything is governed by a probabilty. There exists some mathematical description of a a bunch of possibilities and their probabilities. All the possibilites exist at the same time. It is only when a measurement is taken that the actual value is fixed. As a result a qubit can simultaneously be in the 1 or the 0 state as well as all possible combinations inbetween. It can then interact with a great number of these other particles and exhibit that exponential increase that was refered too. It is only when the data is "read" out that the answer becomes fixed. The trick is however that the system has "tried" every possible state and the result is the one that is observable. If you've got some background in quantum mechanics it'll make more sense.

The whole problem with this wonderful idea is that making structures to store this information, qubits, aren't exactly trivial matters. People can make single qubits (when people refer to quantum dots they're sometimes meaning these) however to make a computer one would have to be able to make a consistent array of these particles which is an incredibly difficult task.

I hope that answers some of you question.
 
thanks for your input, apparantly a quantum computer of 7 qubits has already been achieved. Which is fascinating, hopefully someone will come up with a way to increase that number
🙂

for now i'm stuck with this question digging into the back of my head. I've been doing more research and have found that one link between stopping light and quantum computing is transporting these qubits, as photons also exist in quantum states (many states at the same time). perhaps this is all there is to it..transporting qnuantum information via light

😕
 
and, hey, hopefully they will figure out an instintanious method for sendig data. When you split a particle, and seperate the 2 halves, when you reverse the spin on one, the other reverses at the same tme. We can use that to send data faster than the speed if light. Now that would be nifty.
 
its not splitting the particle, its back to this quantum thing of having it in two places at once. so if you measure the spin, you know the spin of the other one.

yeah its mind boggling..i try not to think too hard about this stuff, afraid my head might explode.
 
Originally posted by: Evadman
Originally posted by: everman
Use Quantum Entanglement for data transfer? It sounds possibly, but I don't know if it could possibly out perform an optical CPU, maybe.
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Hey! Your username is 2 letters away from mine. You are not welcome here! 😛
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rolleye.gif
😛
 
I am not sure but this might be related to "photonic crystals" where there is a bandgap for optical wavelengths. This is anlogous to the bandgap for electrons in semiconductors.
 
I would hazard a guess (though I am not anywhere near an expert on the subject) that the stopping of light (momentarily) is NOT directly related to quantum computing. However, those articles could mean one of two things.

1. Quantum Computing has become a catch-phrase for any type of computing that is largely different in some way then current microprocessor/transistor technology.
2. The ability to stop light is indirectly related to quantum computing in that quantum interactions take place on an extremly small scale and creating a test environment for the study of such interactions is extremely difficult. I would hazard a guess that this ability to stop light will make the study of quantum mechanics and subsequently there application in computing devices substantially easier to do then it was before.

That's my two cents worth....

P-X
 
Originally posted by: RobFDB
As always google is ure flexible friend. Read down and it talks about the impact that stopping light could have on quantum computing. Fascinating subject.

http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm
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[/quote]

looks like this is the answer. Thanks for the link. you know whats surprising is that I skimmed through this article a few times already, i didnt even catch this last part

😀

...Such a computer would work only if there were some way to stop light, change its state, and send it on its way again. Walsworth's team has demonstrated just such a sequence: While a light pulse was imprinted on the rubidium atoms, they made a simple change to the atoms' quantum states. Much to the researchers' delight, those changes were present in the regenerated light pulse.
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