Light-based Quantum Circuit Does Basic Maths 198
Stochastism writes "In yet another small step toward realistic quantum computing Australian researchers have developed a light based 4-qubit quantum computer. It has already calculated the prime roots of fifteen, three and five. 'The quantum circuit pioneered by the Queensland researchers involves using a laser to send "entangled" photons through a linear optical circuit ... The Queensland research group acknowledged that the theorised code cracking ability of quantum computers may be why Australian quantum computer research is in part funded by a US government defence intelligence agency, the Defense Advanced Research Projects Agency (DARPA).'"
Err (Score:3, Interesting)
Of course, the article doesn't help.
Anyone?
Re:MATH (Score:3, Interesting)
Correction: Some non-native speakers of English are taught British English, not all. Moreover, British English has not been the standard worldwide for many years, so outside of Commonwealth countries and Europe, people do not, as a rule, gravitate towards British English.
And no, all this has nothing to do with which dialectic is better. It's just sociolinguistics. American English is the premier language of commerce and political power. It's also the medium of a huge amount of popular culture and marketing. Sooner or later, the prestige will shift elsewhere, just as it started to shift away from Britain after WW2. Sic transit gloria mundi.
We should also keep in mind that for some language groups, English s-plurals are particularly challenging, so the "maths" issue gets obscured by its similarity to a huge amount of genuine errors.
Re:Law of conservation of time (Score:3, Interesting)
I think that the fact that we are here, almost 14 billion years after the universe began, is a good indication that it's not possible to "crash" the universe.
The original numbers plugged in the Drake Equation estimated 10 intelligent civilizations in our own galaxy. Since there are more than 100 billion galaxies, that means there could potentially be more than 1 trillion advanced civilizations.
I would bet at least 1 out of that trillion are much more advanced than us and have managed not to "crash" the universe. Whatever the hell that means.
Re:Law of conservation of time (Score:4, Interesting)
Phenomena like superposition and entanglement are not fully understood from the metaphysical point of view, and there is some hand-waving about that. But the mathematics agrees perfectly with experiment, and that's all we need to know to put the theory to use.
One possibility is that we ask the 'computer' of the universe to do too much computation and end up in an infinite loop, crashed universe, 'dark' part of a mandlebrot-like fractal, etc.
Another possibility is that the 'computer' of the universe will simply abort operations that take 'too long', the quality of our simulation will degrade, and our complex quantum math will result in randomish results.
How do we know building a quantum computer won't break the universe? Well, the things that go on in a quantum computer are the same things that go on in ordinary matter all the time. A speck of dust consists of some 10^20 particles that continually interact with each other according to the same quantum-mechanical laws that govern the interaction of qubits used in integer factorization. Why should the universe care what purpose we use those interactions for?
And in the end, a size/time-N quantum computation can be simulated with 2^N space and in 2^N time on a classical computer (I might be wrong about the exact form of those expressions). Would the universe collapse if we run a quantum algorithm on a PC?
And then there is the possibility held by quantum researchers that somehow the universe can magically perform any amount of complex computation with no cost at all.
This isn't true. Quantum algorithms have real costs that grow with the size of the problem, just like on ordinary computers. (Concretely speaking, we can simulate them on classical computers in deterministic time.)