Re: Anyone seen the 'quantum cryptanalysis' thread on sci.crypt?

[Jim choate <ravage@bga.com>]

> 
> The real roadblock might be that there are limits to how many bits there
> can be in a register.  NIST's recent Quantum Computation conference
> included discussion of the expected lifetime of a computation (what
> fraction of a second the computation would have to complete in before the
> internal state space goes incoherent).  The more bits are bound together,
> the shorter the lifetime of those bits, according to one result.  However,
> the more bits you have the longer the computation has to be.  This suggests
> that any given Quantum Computer technology point will lead to a maximum
> state size (likely in a small number of bits) for a given application.
> 
Something that might be relevant here is that relationship between energy and
lifetime for virtual particle generation. When a virtual particle is generated
it can have a random amount of energy. However, the larger the energy level
is the shorter its lifetime is. It is related to Plank's Constant in a 
relationship that I don't have on hand, but should be in most quantum texts.