The Blockchain supplies us with the key technological function that is required in order to create a real working quantum computer. But in order to understand how it is to be created one have to first understand the fundamentals of the blockchain in terms of mathematical logic. (It is very simple but you have to stay open minded since I used some concepts which are expressed in previous entries.
This is the formula:
A names B
B accept by N (nods)
B names C
C accepted by N (nods)
A names B1 and B2
N/part1 accept B1
N/part2 accept B2
If N/part1 > N/part2 then B is B1
If N/part1 < N/part2 then B is B2
This very simple formula holds the key to decentralization as we know it from the blockchain. however it also shows the direct connection to the uncertainty principle of physics and the limit for a complete logic .
For a full decentralization the flow of information have to be complete. meaning that all nodes have to be exposed to the same information at the same time. However they don't have all the information in real time. One node cant know what the other node decide at point 0 (of time) only at a delay.
"know at the same time" is a limit of information.
one can not act and let everyone know about it at the same time.
Information about an act always comes after the act.
When one act it can not know how everything around him will act at the same moment.
Thus in logic terms. there is no truth at the moment of action since there is no information available at the moment of action for the real state of the system as a whole. Thus every action (decision) at the moment of execution is arbitrary.
There is no judgment (as true or false , good or bad) possible at the moment of action.
A choice made at that point of 0 knowledge (information) is also arbitrary.
But the figure that can describe that arbitrary function can be calculated to a quantum precision.
further more in logic terms contradiction potential can be expressed as the gap between action and information about it . Thus if the fasted flow of information is the speed of light then the minimum computational contradiction factor will be a multiple of nodes to the speed of light.
This figure is the factor of uncertainty in any computer work.
This quantum limit of a decentralized networks can be applied to Godle theorem and to truing complete to resolve the paradox of consistency and decidability.
A single computers is a network . In fact Any "real thing" (something made out of matter) is a network in terms of information flaw. Thus a complete logic applied to a "real thing" will always be incomplete limited by the information speed-of-flow. Whether this information is delivered by a human runner or by light dose not matter in principle only in speed and risks of malfunction (such as runner's health or electrical network capacity )
The only difference between a decentralized network and a centralized network is that in a centralized system the nodes are programmed to choose the longest chain while in a decentralized system the nodes are free to choose the other chain and thus break of the main chain.
If think in terms of a quantum computer in fact it is nothing but a supercomputer made of many computers programmed with a builtin blockchain application in terms of information share and an added order to always accept the longest chain as the new corpus of truth.
The only builtin difference between a centralized network and a decentralized network is that the nodes are either programmed to choose the longest chain (centralized), or programmed for a manual choice by the owner (operator) of the node (decentralized).
Now it is very crucial to understand that even the most centralized system can maintain and support a whole network of individual independent entities which can operate on a decentralized partial blockchains like side-chains.
In fact the fractal structure of nature reviles such play between a centralized network maximizing the benefit of a decentralized function.
Note the first function: A name B. Giving A the power to name B rather then making the nodes decide on it allows to maximize the power of the individuals even in a centralized network. in which the nodes are programmed to accept the longest chain.
No for a quantum computer you need the superposition of bits, and that can only be done in the quantum realm. Anything physical or virtual, is just classical phyics, and is a classic computer.
The quantum computer that you are talking about is a fiction, since indeed computers are real and not virtual. Just like the dead/alive cat in the box, there is no cat in quantum state as there is no computer capable of such state. it is only the state of information itself that is such due to the limitation which indeed are expressed in quantum mechanics .( that Schrödinger's cat example is so stupid to begin with...) A system, any system, can not be "aware" to the true localized state of each part of it thus it is entangled until "observed". This so called observation is described by the correlations of arbitrary choices between two measurement of the same observed event. and it is the same as two choices made by an automated computers network which will have to decide on B1 or B2 as B. The no cloning theorem is like the dabble spending limitation. In life it is our brain that process that information, in bitcoin it is the miners. A cat can be alive and dead at the same time between blocks just like it is in bitcoin but once the information is spread in the network it can only be alive or dead not both alive and dead!!!! (which none have to do with the real state of the cat since it is in a box and we cant verify it . Once verification enters the equation it is not about "naming" any more but the truths of what we already agreed on as "alive". )