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  More qubits than you know what to do withMar 01, 2012 7:54 AM PST | url
 
Added 1 new A* page:Finally knuckled down and used the Copic Multiliner markers for laying lines directly over pencils--that's what I got them for, after all--and I'll be darned if it didn't actually work out pretty well. Huzzah!
 
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IBM just announced that its researchers have developed "superconducting qubits which retain their quantum states up to 100 microseconds -- an improvement of two to four times prior records."
 
Now, if you're like me, you're saying "what the heck is a qubit?" Turns out it's the quantum mechanical version of a regular computing bit; where bits can be either 0 or 1, a qubit can be 0, 1, or...both simultaneously. Yay, quantum mechanics!
 
Now, what a qubit actually is, physically, is sort of left to the imagination, but I guess it's any sort of particle whose quantum states you can manipulate for your own ends; and then in addition to having...sort of...the capability of three states instead of the regular old two, you can actually get more functionality out of it in operations by taking advantage of quantum entanglement and teleportation; I've talked about those before, but basically it's a wacky quantum quirk of particles spawned from the same event (in which case they are "entangled"), where in order for conservation of energy to be preserved, they essentially have to share states--so if you alter the state of one of them, the other one, even far away, changes to match! So by playing with the possibilities of that, using tricks falling under the heading of superdense coding (sounds like the kind I do... :p), you can in effect get the computational power of *two* regular bits out of a single qubit.
 
Anyway, to make a real, functioning quantum computer, you need to have lots of these qubits obeying commands and persisting long enough to execute them and pass along a result. I'm guessing we're still a good long ways off having one of those that's actually better (and not 10 billionty times more expensive) than the computer you're using now, but hey, progress is being made--I just hope they don't call them "quputers" or something similarly awful :p. IBM doesn't talk about how close something that's actually useful is, of course; aside from news of the increased duration of state retention, their news release appears to have been mostly hype, throwing around silly statements like "For example, a single 250-qubit state contains more bits of information than there are atoms in the universe."
 
That caught my attention as something I could actually fasten on, rather than all that nutty quantum-think. So let's think about what it might mean. The observable universe--which is to say, the part of the universe we can hope to see, based on particles from it being able to reach us at the speed of light
 
Image
image by Azcolvin429 (source)
 
--is said to contain maybe 10^80 atoms (that's 10 to the 80th power, ie 1 followed by 80 zeros). Of course we can't see the rest of the universe, so who knows how many atoms or green munchkins it might have, but if it's more or less like the part we can see, and Guth's theory of cosmic inflation is correct, then the universe is "at least" 10^23 times bigger than the observable part, ie containing at least 10^103 atoms. Whew!
 
Now, I'm not entirely sure what "a single 250-qubit state" is supposed to mean, but maybe it means 250 qubits of data. How much is that? Well, if it was regular bits, it would be 2 (two states) to the 250th power, or about 1.8 * 10^75.
 
Dang, that isn't even the number of atoms in the observable universe, much less the universe! Ah, but if this was qubits, which have at least three states, then it would be 3 rather than 2 to the 250th power, or about 1.9 * 10^119 -- which is waaaaay more than the theoretical number of atoms in the universe.
 
So there you go, I guess.
 
Incidentally, that Wikipedia "observable universe" article I linked also has this interesting comment about the possible size of the universe:
If the universe is finite but unbounded, it is also possible that the universe is smaller than the observable universe. In this case, what we take to be very distant galaxies may actually be duplicate images of nearby galaxies, formed by light that has circumnavigated the universe.

In which case, who need qubits? :P
 
 
 
 
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