by gill1109 » Fri Jul 05, 2019 9:30 am
Heinera wrote:I wouldn't call it "icky", but in contrast to most other theorems in physics, Bell's theorem is completely useless if you work in another field than Quantum Foundations or Philosophy of Science. Most other mathematical theorems that physicists care about are of the type where you can replace something complex in a theory with something simpler and more easily calculated, and appeal to the teorem to argue that they are equivalent. Those theorems are part of the physicist's tool box. Bell's theorem is in a sense the opposite; it "merely" tells you what mathematical structures won't work if you want to achieve a particular result (the QM correlations).
Well, Bell's theorem does tell you (if you believe that the world is run by QM) how to do secure cryptographic key distribution, how to do perfectly secure random number generation, and lots more. So it is the key to a whole heap of applications, some of which are already being marketed by clever entrepreneurs and used by government "defence" organs...
Amusingly, long ago Luigi Accardi together with a Japanese colleague was already *selling* a classical quantum key distribution system by exploiting the detection loophole to "fake" quantum correlations. Of course, since it was actually a classical system, it would have been easy for an eavesdropper to break in and no-one would notice. That was before the various experimental loopholes were rather thoroughly explored and we learnt how to mitigate or even abolish all of them (thanks, in particular, to my own work, inspired by the work of people exactly like Accardi. I needed to set up a bet with him that he could *not* win, except by a small chance which I knew).
[quote="Heinera"]I wouldn't call it "icky", but in contrast to most other theorems in physics, Bell's theorem is completely useless if you work in another field than Quantum Foundations or Philosophy of Science. Most other mathematical theorems that physicists care about are of the type where you can replace something complex in a theory with something simpler and more easily calculated, and appeal to the teorem to argue that they are equivalent. Those theorems are part of the physicist's tool box. Bell's theorem is in a sense the opposite; it "merely" tells you what mathematical structures won't work if you want to achieve a particular result (the QM correlations).[/quote]
Well, Bell's theorem does tell you (if you believe that the world is run by QM) how to do secure cryptographic key distribution, how to do perfectly secure random number generation, and lots more. So it is the key to a whole heap of applications, some of which are already being marketed by clever entrepreneurs and used by government "defence" organs...
Amusingly, long ago Luigi Accardi together with a Japanese colleague was already *selling* a classical quantum key distribution system by exploiting the detection loophole to "fake" quantum correlations. Of course, since it was actually a classical system, it would have been easy for an eavesdropper to break in and no-one would notice. That was before the various experimental loopholes were rather thoroughly explored and we learnt how to mitigate or even abolish all of them (thanks, in particular, to my own work, inspired by the work of people exactly like Accardi. I needed to set up a bet with him that he could *not* win, except by a small chance which I knew).
