Re: Quantum computers and Bitcoin

[hamiltino]

In regards to mining.

Iv'e heard there is a few minutes delay for when the difficulty of bitcoin changes. During this delay a Quantum Computer could solve all the algorithms before the difficulty increases.

Changes in the the bitcoin SHA-256 security or the speed in which the change in difficulty comes into effect needs to be made before any quantum computer starts mining with capabilities which are orders of magnitude greater than current computing power.

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[gmaxwell]

Iv'e heard there is a few minutes delay for when the difficulty of bitcoin changes

You've heard incorrectly.

During this delay a Quantum Computer could solve all the algorithms before the difficulty increases.

This suggests a pretty substantial misunderstanding of what a quantum computer does. In any case, your conclusion doesn't make any sense.

[coinprize]

In regards to mining.

Iv'e heard there is a few minutes delay for when the difficulty of bitcoin changes. During this delay a Quantum Computer could solve all the algorithms before the difficulty increases.

Changes in the the bitcoin SHA-256 security or the speed in which the change in difficulty comes into effect needs to be made before any quantum computer starts mining with capabilities which are orders of magnitude greater than current computing power.

I heard about someone talk about such kinds of topic.
They will guess something when they are not familiar with BTC.

But it's not a mainstream news. 

[hamiltino]

Iv'e heard there is a few minutes delay for when the difficulty of bitcoin changes

You've heard incorrectly.

During this delay a Quantum Computer could solve all the algorithms before the difficulty increases.

This suggests a pretty substantial misunderstanding of what a quantum computer does. In any case, your conclusion doesn't make any sense.

I have little understanding compared to physicists and technologists but more then the majority of the populace(unless i am more ignorant then them).

All i know of quantum computing is that it can be at the 0 and 1 state at the same time or one or the other. I was listening to D-wave founders on youtube. And in theory one processor could act like it was many many processors due to quantum entanglement.

Good video: http://www.youtube.com/watch?v=fArXhQBLDWE

[kjj]

We seriously need a "time out" room for people that post this topic for the Nth time without searching.

The very, very short summary which includes absolutely nothing that I haven't posted at least once or twice before:

Quantum computers running Shor's algorithm have some chance of seriously challenging the security of ECDSA at some time in the future, probably 2+ decades from now.

Quantum computers running Grover's algorithm have pretty much no chance at all of hindering mining in the lifetime of anyone old enough to read this post today.*

D-wave boxes do something called annealing.  Opinions are still somewhat divided, but so far it appears pretty likely that the annealing they are doing is actually quantum in nature.  Quantum annealing is useful for implementing neither Shor's algorithm, nor Grover's algorithm.

Work on general purpose quantum computing devices is underway, with the current world record (I think) standing at 21=3*7. **

* Grover's algorithm is fantastically powerful.  It would destroy mining (or rather, it would force a switch to a new hashing algorithm).  The catch is that to use it, you have to physically build a single stateless circuit to implement whatever you are trying to search, and you have to build it out of reversible gates, and you have to keep the whole thing coherent and stable.  Building even a classical stateless circuit for SHA2-256 is still in the realm of deep fantasy.

** Humorous quote: "The algorithmic output is distinguishable from noise, in contrast to previous demonstrations."