Does Quantum Mechanics forbid some type of Von Neumann machine for the Universe?
Spin is ideal as a constituent of a Von Neumann machine. DNA & RNA are at some level a storage and implementation of information. It does not have to be just in bits.
Yes, the universe manages to create dna, which indeed, is a powerful information storage device and implementation method similar in some respects to a classic Von Neumann machine. Does DNA use quantum states or is it purely topology of chemical compounds to store information? - its a little out of my field.
I would guess that the universal Von Neumann machine - if it exists- would be in some ways similar to the dna model except it could make use of quantum states more than chemical compounds. In fact quantum superposition would give it increased power compared to classical methods.
No this no sense. Von Neumann is computer not dna - look at theory.
Well, the basic principle of implementing an active system that uses data and algorithms can be done in many ways and the universe is well capable of it - as dna proves. Quantum ways would be highly effective because of superposition leveraging the computing power - look at theory.
I don't understand the question being asked in this thread.
There are two different things out there which are commonly described by the term "Von Neumann Machine".
One is the sort of generic idea of a self-replicating machine, which often is called a "Von Neumann Machine" because Von Neumann once gave a lecture proposing such a thing.
The other is the idea of a machine or computer with a Von Neumann Architecture; such machines sometimes get referred to as "Von Neumann Machines". The Von Neumann Architecture refers to the idea of a computer which is structured in such a way that there is a memory where a stored program co-resides with storage space; and a CPU-type unit which operates on this memory. Basically all computers which are built in the real world are Von Neumann machines in this sense.
Some of the comments in this thread seem to be referring to one type of "Von Neumann Machine", others to the other. What kind of "Von Neumann machine" are we talking about? And what would it mean for there to be a Von Neumann machine "for the universe"?
I'm surprised no one has yet mentionedhttp://en.wikipedia.org/wiki/Laplace's_demon"
Yes, thanks for that very good descriptions of Von Neumann Machines - I'll take both,
and mention of Laplaces Demon.
Because this is a quantum physics section we can only really discuss that, except
to say basic sub-atomic particle types (there are not so many) and fields can be
mathematically modelled as algorithmic templates with properties and behaviors
accessible from, and to, 3/4 space. As indeed, 3/4 space itself. Then each particle becomes an 'object' of its type template with its own phenomology as defined by its template and properties.
Interaction behaviours and field dynamics are then fully defined in the templates.
This would then provide a comprehensible ontology for such phenomena as entanglement
correlations, distributed wave functions in real physical space, and such things as virtual photons in electron-proton interactions.
No, STANDARD MODEL for physics not Von Neumann. He do computer.
I do not know any analysis that accepts a Von Neumann Machine for the Universe itself, have you got a proof of this in any way or is it in the realm of science fiction?
We can build a physical VN machine (architecture), and use it to simulate reality to some precision, but not exact precision.
However the first likely applications for machines built with quantum logic will be: simulating QM.
Cannot we simulate QM already in a PC or Mac in a smaller defined universe? Entanglement would need a random number generator pointed at both entangled particles. Or would it need two random generators pointed at both particles? Not quite sure how Bell's Inequality would be simulated in a normall computer. Maybe its impossible and we need quantum computers.
We can't simulate even the standard model of QM on supercomputers, it takes a lot of time because QM is NP-hard, for a polynomial-time VA (note: a VN machine isn't a VA = a PC; a PC = a VN* + a real machine )
A non-deterministic Turing machine (NTM) differs in that...
many different actions may apply for the same combination of state and symbol...
How does the NTM "know" which of these actions it should take?
...the machine "branches" into many copies, each of which follows one of the possible transitions. Whereas a DTM has a single "computation path" that it follows, an NTM has a "computation tree". If any branch of the tree halts with an "accept" condition, we say that the NTM accepts the input.
BTW, 'nondeterministic' is a misnomer. it is perfectly deterministic.
Separate names with a comma.