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A "Photon Machine Gun" For Quantum Computers
An anonymous reader writes "Generating entangled photons in a reliable way is impossible right now, stalling the development of the optical quantum computers that would use entangled photons as quantum bits (qubits). Because entangled photons can only be produced at random — which takes time — the most powerful optical quantum computing device use only 6 qubits. UK and Israeli quantum physicists have designed a blueprint for a 'quantum machine gun' that fires out barrages of entangled photons on demand. They think within a few years this device will be built, and could lead to quantum computing using 20 to 30 qubits. Every additional qubit doubles the computing power, so these quantum computers could outperform any existing classical computer, the researchers say. The quantum machine gun is described as 'one of the most exciting theoretical proposals I've read in five years' by a leading quantum physicist." The research was published in Physical Review Letters earlier this month.
Harmful harmful force? Dude i think you need to re-evaluate your worldview if you want to blame the group being constantly attacked and threatened with the explicit goal of genocide for everything wrong. The mere presence of jews in the middle east produces the reaction you see from Hamas and friends, whether or not Israel was officially a state would have fuck all to do with anything other than the success of those attempts at genocide.
Hell Hamas' own govt charter explicitly blames the jews (merchants of death) for everything from the french and russian revolutions to both world wars while outright demanding the death of every jew and anyone who refuses to participate in said genocide.
A bullet may have your name on it but splash damage is addressed "To whom it may concern."
Ok, I just wrote a lengthy reply, and then by accident hit "refresh", and all the text was gone :-(
Therefore here the short version:
The Tao of math: The numbers you can count are not the real numbers.
Bad analogy time.
The simplest way to factor a large number is to just try to divide it by 2, by 3, etc. Once you've divided it, you now have 2 smaller numbers to factor. Repeat until you get a prime. This takes a long time for a large number because you have to try it over and over again.
With a quantum computer you can do all of these computations in parallel, and then arrange for all of the non-factors to cancel each other out, meaning that you can only measure a legitimate factoring. (Getting all of the non-answers to cancel out is the trick in quantum computing, and it isn't a particularly easy one to pull off. These are not general purpose computers!) If it keeps giving you 1*n as your factoring, eventually you conclude it is prime. Otherwise the first time it gives you something else, you've broken the number down into 2 easier ones.
To break RSA you only have to factor one number. So everyone cites that as the classic problem. But you can't factor a number you can't put in. With 20-30 qbits you can only input 20-30 bit numbers so you can't factor anything bigger than that. By contrast a motivated person these days with a few PCs and a few months to devote to it can factor a general 600 bit number. Most people's codes are 1024 bits or longer.
Therefore this research is cool, but any claim of an immediate threat to cryptography is waaay overblown.
First, let's look at a fair attempt to explain why quantum indeterminacy is not just the same thing as classical indeterminacy (like your two particles, which by your question were presumably determinate in the classical model, at least until they became entangled). You seem to be reasoning much as the following note claims early quantum physicists tried to, when they first grappled with Heisenberg's uncertainty principle and the question of knowing the position and velocity of an electron simultaneously. I give you someone deliberately trying to put the concept in normal, natural language and not use any actual math:
http://www.uhh.hawaii.edu/~ronald/310/Quanta.htm
One point is, the interpretation that we can't know both position and velocity at the same instant, therefore the electron doesn't have both at the same instant, doesn't explain that thing you refer to as "with no regard to distance". This is what sometimes gets called "Spooky action" and is related to non-locality in general. Starting from the interpretation that it's not our not knowing that causes the indeterminacy but the indeterminacy which causes our not knowing turns out to be putting the horse back in front of the cart. Once people started working from the idea that the indeterminacy is fundamental and not like your example of the balls (where there is a definite color for each, and the observer just doesn't know it yet), they started making progress on figuring out how entanglement could be faster than light.
http://www.absoluteastronomy.com/topics/Quantum_indeterminacy
This is about what non-locality really means: One consequence is that we can't assign a local cause (such as: a localized observer hasn't looked yet) to explain why something on the quantum level is determinate, or we lose the ability to explain how the faster than light part happens.
Just as the original QM problem was about determining position and velocity, talking about "non-localizable" (position), and instantanious/faster than light (velocity) is two ends of the same stick. The more you prove that the action happens much faster than the limitation of light-speed, the more you can't claim the action is caused by anything in a particular locale.
Who is John Cabal?