[Cryptography] Post Quantum Crypto

[Ron Garret]

On Nov 15, 2015, at 11:58 PM, Viktor Dukhovni <cryptography at dukhovni.org> wrote:

> Does anyone know of any credible references to suggest that QC is
> bottle-necked on progress in Physics beyond QED (let alone beyond
> the Standard Model)?

It’s the exact opposite.  The theory of QC is completely worked out, and the basic principles have all been demonstrated in the lab.  It’s purely an engineering problem, but a really really hard engineering problem.  The reason it’s hard is that you have to control entanglement with great precision.  You need to build a system with a large number (hundreds or thousands) of mutually entangled degrees of freedom, none of which are entangled with anything else, and you need to maintain all of those entanglements as the system evolves through quantum gates.

A very rough analogy: take an old-style wooden pencil and balance it on its end.  Now try to balance another pencil on top of the first one.  If you’re very, very careful you can probably manage it.  Maybe even three.  But to do practical QC you need to make a tower of several hundred pencils, and it needs to stay balanced for a minute or two.

rg