Baby Steps Toward Quantum Computers 308
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."
Re:can someone qualified answer this question (Score:3, Insightful)
Yes, fast (Score:3, Insightful)
Re:Analogue vs Digital (Score:5, Insightful)
In searial you do one instruction per peice of data. In parallel you try EVERY piece of data in one instruction.
Some problems are trivial in serial but hard in a parallel and other problems are trivial in parallel but hard in serial.
Simple Example:
Iterative calculation are great in serial but aren't that good in parallel as you can calcualte the second value till you have the previous value.
The Famous example:
The big thing that quantum computers will do is make parallel problems trvial. The big two being simulations and cryptology. Cryptology is only hard because you have to try so many different combinations. Quantum would allow you to try EVERY combination at a single time. This make encryption almost useless at any key length.
It's also usefull for simulations like ray tracing and vector maths where you have a complex eqation where you just have to run for every possible variable.
So ever is a single iteration takes 1 hour for a quantum computer instead of 100th of a second for normal computers it will change the world. Breaking a key 2048 bit key will take exactly 1 hour instead of million+ years. Rendering a frame will take 1 hour on a single computer instead of 4 hours on 1000+ computers.
That being said it would be useless for Word, Excel or Firefox
Imagine a quantum computer that does 5 Hz out perform a cluster that does 5 TeraHz.
Re:Analogue vs Digital (Score:3, Insightful)
It's been proven that quantum computers are no better than classical computers at sorting (both O(n log n), although they are better at finding something in an unsorted database (Grover's algorithm does O(sqrt(N)), instead of O(N) classically).
No one has proven that quantum computers are faster than classical computers for factoring. We just know of a fast algorithm for a quantum computer and not a classical computer. It's likely that quantum computers are much faster there, though.
Re:How do you measure spin? (Score:2, Insightful)
A qubit
The spin of an electron
The polarization of a photon
They are equivalent that they can each be representated by a 2 dimensional complex vector, where you don't care about the overall phase (and 0 isn't allowed).
Every played around with polarized lens filters? You have a horizontally polarized lens followed by a vertically polarized lengs, and no light goes through.
You add one that is polarized at 45 degrees, and suddenly 1/8th of your orginal light is going
You can think of your lenses as measuring your qubits (polarization of each of the photons), in different basises, and only letting the ones that were measured as a |0> through.
Can't be used for communication? (Score:1, Insightful)
-Agret
Re:Answers anyone?? (Score:3, Insightful)
Re:Analogue vs Digital (Score:2, Insightful)
Re:Buy stock now!! (Score:0, Insightful)
Re:Analogue vs Digital (Score:3, Insightful)
You cannot measure anything without affecting it. That's one of the basic properties of quantum mechanics. Especially, if you have an entangled pair, and measure one parner, then you destroy the entanglement. Always, and inevitable.
Even if you try to circumvent it by first having it interacting with something else and then measuring that other thing: If by measuring that other thing, you get information about the partner (more exactly, about the value of one observable of that partner), then it means the "circumvention system" was included into the entanglement, and your entanglement will be gone as soon as you measure that.
Worse, measuring the original entangled pair without the "circumvention system" will have them behave as if they already had been measured, that is, you cannot make use of that entanglement without having access to all systems which take part in it, which now includes the "circumvention system". Actually, that's how decoherence works: The interaction with the environment causes the environment carrying information about the system ("measuring" the system), and therefore destroying coherence since you cannot completely know/control that environment.
I don't want .. (Score:2, Insightful)
I don't want a quantum computer as much as a quantum network card.
If the transmission distance is unlimited, I would set up a access point at home (connected to the net) and carry around my quantum networked device.
Even better would be to use this technique to communicate with space probes (ie. Mars rovers). No more waiting for data.