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How does something like this affect bitcoin? Putting the cost of the machine aside, would a computer like this be able to mine coins at high speeds using relat

How does something like this affect bitcoin? Putting the cost of the machine aside, would a computer like this be able to mine coins at high speeds using relatively little electricity. Seems like it could crush the market with inflation.

Jach 14y ago
It's an interesting technical question: analogous to the quantum fourier transform, is there an algorithm only quantum machines can run that computes sha-256 hashes faster? I don't have the answer. (I know sha-256 is O(N) normally.) As for bitcoin, though, I don't think there's too much to worry about. If a quantum algorithm grants a complexity speed up (or some sort of deal-breaking cryptographic weakness is discovered in sha-256 for that matter), I imagine the network could agree to update to a new protocol using a different hash, if that was the proper solution. If a quantum computer just gave integer-factor speedups such as ASICs are currently doing to GPUs and FPGAs, then I suspect by the time a quantum computer is made that can efficiently mine bitcoins, enough can be made at once that, just as we're seeing with ASICs, quite a lot of miners will grab them (avoiding a 51% issue) and the difficulty will simply rise. Edit: https://bitcointalk.org/index.php?topic=78693.0 https://bitcointalk.org/index.php?topic=78693.0 tells me http://en.wikipedia.org/wiki/Grover%27s_algorithm http://en.wikipedia.org/wiki/Grover%27s_algorithm would work, making the algorithm O(sqrt(N)) and effectively making the problem of finding a sha-256 hash into finding a sha-128 hash.
Ygg2 14y ago
I don't think it will work like that. As I repeated ad nauseam above, this is an adiabatic quantum computer, not gate quantum computer. Here is a quote: > Computers using D-Wave's devices will always > differ from gate-based quantum computers in one key way: > D-Wave's devices do not lead to universal computers that > can be programmed with any algorithm, as an ordinary computer can. > Instead, says D-Wave's Colin Williams, their chips focus > on solving a particular class of optimisation problems. > "That's such an important class that commercially it is > a much better strategy than trying to make a universal machine." Perhaps the problem of bitcoins can be reduced to hill/valley optimization, but I don't think that's how bitcoin works.

Jach 14y ago

It's an interesting technical question: analogous to the quantum fourier transform, is there an algorithm only quantum machines can run that computes sha-256 hashes faster? I don't have the answer. (I know sha-256 is O(N) normally.) As for bitcoin, though, I don't think there's too much to worry about. If a quantum algorithm grants a complexity speed up (or some sort of deal-breaking cryptographic weakness is discovered in sha-256 for that matter), I imagine the network could agree to update to a new protocol using a different hash, if that was the proper solution. If a quantum computer just gave integer-factor speedups such as ASICs are currently doing to GPUs and FPGAs, then I suspect by the time a quantum computer is made that can efficiently mine bitcoins, enough can be made at once that, just as we're seeing with ASICs, quite a lot of miners will grab them (avoiding a 51% issue) and the difficulty will simply rise. Edit: https://bitcointalk.org/index.php?topic=78693.0 https://bitcointalk.org/index.php?topic=78693.0 tells me http://en.wikipedia.org/wiki/Grover%27s_algorithm http://en.wikipedia.org/wiki/Grover%27s_algorithm would work, making the algorithm O(sqrt(N)) and effectively making the problem of finding a sha-256 hash into finding a sha-128 hash.

Ygg2 14y ago

I don't think it will work like that. As I repeated ad nauseam above, this is an adiabatic quantum computer, not gate quantum computer. Here is a quote: > Computers using D-Wave's devices will always > differ from gate-based quantum computers in one key way: > D-Wave's devices do not lead to universal computers that > can be programmed with any algorithm, as an ordinary computer can. > Instead, says D-Wave's Colin Williams, their chips focus > on solving a particular class of optimisation problems. > "That's such an important class that commercially it is > a much better strategy than trying to make a universal machine." Perhaps the problem of bitcoins can be reduced to hill/valley optimization, but I don't think that's how bitcoin works.