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Single Photons Bounced Off Orbiting Satellite
KentuckyFC writes "If we're ever going to benefit from the perfect security of quantum communication, we're going to need ways of transmitting entangled photons around the globe and certainly further than the current record of 144km through the atmosphere. Anton Zeilinger at the University of Vienna and colleagues have taken an important step towards this by bouncing individual photons off the Ajisai geodetic satellite (essentially a space-based disco ball) which is orbiting at 1400km. The group says the experiment is an important proof of principle for satellite-based quantum communications."
From my understanding it does serve a practical purpose in that intercepting the message changes it. Thus while you can't stop people from tapping into your message, you do have instant feedback about when that happens.
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Real security improvements. There is no proof that there is not a trivial way to factorise multiples of large prime numbers, which is the basis of most current encryption standards. There are alternatives, but again there is no proof that these cannot be cracked quickly.
;-)
Even though it is unlikely that someone will have a mathematical breakthrough that would allow your PDA to break 2kb keys, we know that a lot (maybe all) of these algorithms could be cracked with a quantum computer. It is possible that the US NSA already has such a computer, maybe together with Russia, China and Bill Gates
Quantum encryption is proven to be uncrackable without showing that someone is listening. With a preamble of two-way communications you can have a connection that is proven to be absolutely secure, and no breakthrough in mathematics or technology will break it.
Breaking quantum cryptography is not hard, it is impossible. The security is guaranteed by the laws of physics. Unless quantum mechanics is flat out wrong, it can never be broken, period. And saying quantum mechanics could be wrong is like saying gravity could be wrong.
About quantum computing, it's actually closer to providing new computational powers than you might think. In terms of a powerful, programmable computer that can factor large numbers, we are a long way off. But in terms of being able to simulate certain quantum systems that current supercomputers cannot, we are fairly close.