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Light-based Quantum Circuit Does Basic Maths
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).'"
1 qubit = 1 bit, I believe
Sorry, wrong. Math and maths are both colloquialisms, and neither is more valid than the other. Just Britith vs American english tendencies, mostly.
http://www.answers.com/maths&r=67
Thanks fo the rant, though.
You can use ANY quantum mechanical system with two discrete states as a qubit, just as you can use any classical mechanical/electric system with two discrete states as a bit.
Typically with photons, it consists of the direction of polarization of the electro-magnetic field associated with the photon. Straight up and down represents one state, horizontal represents the the second state, and the photon can be in a superposition of both of these states.
Saying that photons get "destroyed" is irrelevant so long as we can measure the photon's polarization when it gets destroyed because as soon as we measure the polarization, the quantum state of the photon is destroyed anyway and becomes worthless to us. This is true of any quantum mechanical system, so whether the system representing the qubit sticks around or disappears after being measured (whether a photon, electron spin, or otherwise), is only a matter of logistics of the quantum computer, not of the actual computation.
The laws of probability forbid it!
Who to go with, the military funded scientists working on a solid foundation of one of the most tested and proven physical theories mankind's best and brightest conceived of and developed with working models or a random blogger who can't get his head around the uncertainty principle.
Well, fair enough, Einstein himself quoted 'God does not play dice' on this very issue, before coming to terms with it. You might have the best of intentions but unfortunately you're off track. Regardless of what anybodies opinion is the quantum uncertainty model accurately predicts all available data, and theories that coincide with empirical evidence are useful and usable no matter how small or great an understanding we have of the underlying processes.
Come up with a simpler theory that fits all the data and I'll gladly accept your claims of crackpottery, otherwise open your mind a little and realise that regardless of a deeper understanding, if the math fits, we can do it, ergo quantum computing is not just feasible, but is already happening as we speak in labs the world over, like the one in TFA.
The article mentions things called "prime roots." This is not a standard mathematical term. Rather, considering the context, quantum computing, and its most discussed potential application--quantum cryptography--it is likely that what was actually computed were primitive roots.
..., and modulo 5, this becomes 2, 4, 3, 1, 2, .... The first occurrence of 1 is for 2^4, hence k = 4 = 5-1.
For the sake of completeness, a primitive root of a prime p is an integer r such that the smallest positive value of k such that p divides r^k - 1 is k = p-1. For large primes, finding primitive roots is not a trivial task. For example, r = 2 is a primitive root of p = 5, since the positive integer powers of 2 are 2, 4, 8, 16, 32,