Slashdot Mirror
Research Team Makes Quantum Computing Progress
Timogen writes to tell us Wired is reporting that a research team is reporting that they have found a way to "controllably couple qubits" bringing us one step closer to quantum computing. "In classical computer science, bits -- or binary digits -- hold data encoded as ones and zeros. In quantum computing, data is measured in qubits, or quantum bits. As such, a qubit can have three possible states -- one, zero or a "superposition" of one and zero. This unique property theoretically makes quantum computing able to solve large-scale calculations that would dwarf today's supercomputers. But qubits in isolation are not very useful. It's only when they can be connected to one another that large-scale processing becomes possible."
The Ark. That's right: Noah's Ark.
Qubits can have an infinite number of states between 0 and 1 (inclusive). "Superposition" does not describe a single state, it just means that it's somewhere in between.
It was a bit of a leap.
Engineering is the art of compromise.
The tri-state computer: Yes, no and "maybe".
Then again, every time I use Windows, I already have the hunch that this "maybe" has already been implemented. If only in software so far.
We used to have a Bill of Rights. Now, with the rights gone, all we have left is the bill.
There are two possible end states: the researchers made progress or not.
But until you actually make an observation by clicking on the link and reading the article, the outcome will still be indeterminate.
Slashdot's got an article that says "Timogen writes to tell us Wired is reporting that a research team is reporting that"...
Just junk food for thought...
Kind of. But then you can still create qubits in entangled states, like, upon measuring two qubits you get always one "1" and one "0" , but you don't and cannot know which is which until you measure. You can't do that with an analog computer.
It feels as if we were recreating computing, making the first steps again that were made during the 1920s-1940s in computing.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
...I could go on all day...
...a qubit can have three possible states -- one, zero or a "superposition" of one and zero. This unique property theoretically makes quantum computing able to solve large-scale calculations that would dwarf today's supercomputers. Trying to understand this claim better, I followed wired's link to this article, which states:
...in a QC, the bit is upgraded to a quantum bit, or qubit, that doesn't need to choose between 1 and 0. It can be both at once. As a result, a memory array of n qubits can represent every number between 1 and 2^n simultaneously. A QC's capacity doubles with each additional qubit. It may be humbling that the world's largest QC is currently only 7 qubits in size, and can barely process single-digit numbers. But a QC of 333 qubits would be able to perform operations instantaneously on every number between 1 and a googol (10^100), a value considerably larger than the number of atoms in the universe. To carry out addition or multiplication on every positive integer between 0 and 10^100 would take one of today's supercomputers several quadrillion years as it marched through one number at a time. But a QC would perform the calculation all at once, and it'd be done. I can (kinda) understand how n qubits can store every number between 1 and 2^n, and I can (very vaguely) imagine how that allows one to perform calculations on all those numbers simultaneously. Assuming all of that is true and good, what would one do with the output? For example, let's say I take sqrt(1 to 2^n) and get glurg as a result. Does glurg really hold the sqrt of all those numbers, and if so, how do I access them individually?It's a Q-Bert leap.
Quantum computers don't turn NP into P. I.e. they don't let you solve NP problems (where recognizing a correct answer is very easy but you have to test all answers to see which is correct) in an amount of time that is a polynomial function of the size of the input.
There are two specific algorithms for quantum computers that have a big impact on encryption:
Shor's algorithm lets a quantum computer factor a number in polynomial time. It requires a number of qubits that is some multiple (greater than 1) of the number of bits in the number. So, once we have quantum computers with a few thousand qubits, all encryption mechanisms based on the difficulty of factoring numbers (which is most mechanisms) are broken.
Grover's algorithm lets a quantum computer look up an entry in an unordered dictionary in N^.5 time, where N is the number of entries in the dictionary.
Grover's algorithm, if I understand it properly, is a Big Deal. When they say "look up an entry in a dictionary", they really mean "give an entry for which an arbitrary algorithm returns a desired value". Essentially, it means you can solve any NP problem in N^.5 time. For example, with a simulation algorithm you could find a satisfactory design out of 100,000,000,000,000 different computer designs in 10,000,000 applications of the simulation algorithm, as opposed to the 100,000,000,000,000 applications it could take on a normal computer.
Another example of applying Grover's algorithm would be cracking a password (regardless of the encryption algorithm used). Let N be the number of possible password combinations. On average cracking a password would take N/2 applications of the encryption algorithm using a normal computer; it would take N^.5 applications using a quantum computer.
Quantum computing doesn't invalidate encryption, but real QC would essentially invalidate encryption algorithms based on the difficulty of factoring large numbers and substantially reduce the difficulty to crack any other algorithmic encryption.
Of course, one time pads are still totally unbreakable if used properly...
It must have been something you assimilated. . . .
The more progress we know the researchers made the less we can know about how close they are to a solution.
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