Bitcoin Forum

Quantum computing and Bitcoin really needs to be discussed.

How will Bitcoin survive quantum computing?

http://europe.newsweek.com/quantum-computers-kill-bitcoin-cryptocurrency-509053

hahhahaha, these old school newsmedia outfits are really leading the discussion, lol. I expect the quality of their assessment is going to be less polished than what the average Rookie Bitcointalker came out with 18 months ago.

HEY GUYZ - BITCOIN DOOMED BECAUSE QUANTUM BLAH BLAH BLAH

Do these people even TRY anymore? We've been over this again and again, and this fucking turd of a topic keeps coming up somehow.

These articles keep popping up once in a while. If quantum computing advances to threaten Bitcoin, Bitcoin would just evolve to use quantum-resistant algorithms (instead of public key-private key security)

https://cointelegraph.com/news/the-arrival-of-quantum-computing-threat-to-bitcoin

At the risk of being off-topic, what exactly is quantum computing and how does it affect bitcoins? ???

Classical computing first. We're using classical computers. Binary digits (i.e. "bits") to represent data and code, and logic gates for the calculating parts. The binary digits are generated by a signal generator controlled by a digital clock. When the voltage in the circuit is above a certain threshold, the components are designed to detect that signal as a "1". When the voltage is zero, the components are designed to detect that signal as a "0". The logic gates use these 1's and 0's for calculations, and the calculations can be used to draw to the screen, accept input from mouse or keyboard, play games etc.

Quantum computing is entirely different. Instead of each unit of computation being binary (i.e. only 2 possible states), the units instead have an infinite number of states. This puts their computing power in a completely different league to the Von Neumann binary computers we know today. Binary arithmetic is very limiting; only addition can really be performed directly. To achieve subtraction, multiplication or division in binary computers, some unnatural seeming maths needs to be used. This is perfectly accurate, but involves many more steps than seems necessary to a human observing how it's done (but all those steps are necessary).

With the infinite number base that Quantum Computing could provide, bizarre seeming workarounds are unnecessary. And the sort of massively parallel problems that cryptography poses (i.e. Bitcoin's cryptographically immutable blockchain) could be solved with a tiny fraction of the server farm effort that binary computing would use to crack it. The problem for making QC a non-laboratory reality is this: quantum computing units (qubits as opposed to bits) must be composed of a single atom or atom scale particle. The various sub-atomic particles that make up a qubit are where all the quantum effects to compute with come from. In order to get even a very basic setup running, you really need that laboratory. All quantum computers have been lab based experiments, and I'm not aware of any example that (yet) outperforms binary computers for the same task. And to achieve something that impressive, it's an expensive setup (for which your local tyrants will want you to seek permission or a license).

So in short, they're astoundingly powerful computers that would take what's possible with computing to a whole other level. Once they get out of the "...in 10 years" pipedream stage, that seems to go on forever.

Very nice Carlton, you surprise me all the time!  ;) Good explanation.
As far as I know I would add one more thing: one problem with QC is that the more qubits are involved the more complex it gets to handle the quantum interference.

Well, you've hit the limits of my knowledge there Karatama, I wasn't aware of how difficult a problem signal interference becomes as you increase the qubits in an array.


Something I forgot also: not only can QC's calculate using an infinite number of states, but they could also exhibit every one of those states simultaneously, at a given moment in time. Binary computers can only represent one state at any one time.

(the very high frequency of the clock speed creates the illusion that binary computers are doing more than one task at once, in reality binary computers are just switching between multiple tasks very very rapidly, too fast for a human observer to notice..... most of the time! You can see behind this particular trick when your computer becomes overloaded with tasks and the mouse pointer gets that freeze-frame effect, that's because the processor can't interrupt the other tasks quickly enough to make the pointer move smoothly)

Thanks. Very informative. You don't seem overly concerned about QC and Bitcoin.

Good description, but a couple of nits...
1) macro size quantum bits are being used every day by seth lloyd. They are done with rotating superconducting  currents. Still an expensive lab setup, but it shows you don't need to manipulate quantum sized objects.
2) seth predicts we'll have 50-500 qubit computers in less than 10 years.
3) if i'm not mistaken, physicists have finally come to believe that dwave simulated annealers (as sold to google etc.) are in fact exhibiting quantum effects. Perhaps not as directly as dwave would have us believe, but nevertheless that makes them faster than conventional computers.

Hmmmm for Mr. mmmmm.... interesting.

Superconducting currents? Yikes, so cooled to absolute zero then? (or have superconductors come on since I last looked at this stuff?). And I'm not sure if point 2 is really a nit, he did say 10 years^TM, did he not? :D Still, I agree that the progress from the field that you're presenting makes the whole QC endeavor sound much more realistic than any previous indications. Now, just need to discover those superconducting substrates that function at room temperature.... tell us more if you have some.

They are integrated circuits cooled to liquid helium temps (like 15mK).  I did mention it was still expensive :)

re 2): i typoed. he actually said (i think) 50-5000 qubits in 5-10 years. He said this at least a year ago irc, so it's 'less than 10 years' from now (5-10, +/- 4 years) :)

I like seth. he's a physics phd, but call himself a quantum mechanic. heheh.
his job title is prof of quantum mechanical engineering, which he says is prof mech eng.

If you have much of an interest in the field generally, you'll like this (4 year old) intro to quantum computing and how he is using it to hack the universe computer. :)
https://www.youtube.com/watch?v=I47TcQmYyo4

Here's a very recent interview where he's talking about the whole field, progress etc. (audio+text).
https://www.edge.org/conversation/seth_lloyd-quantum-hanky-panky

Room temp superconductors aren't here yet (afaik), but things look promising.

Thanks for that harry, bookmarked. Seth Lloyd, quantum mechanic, I like it lol. When contemplating fixing your QC, I bet he sucks through his teeth and says "woah, this might be a pricey job" :D

Thanks to both of you for these exciting insights. I am always eager to learn more in this field even if I'm not a techy. I just love the matter.
Very informative thread, bookmarked as well for further readings.

What is the reverse equation to get the private key from the public key ?

That is if Bitcoin becomes successful.

I think the question is how are people that are using Supercomputers/Quantum Computers going to store their data?

Sure miners will lose out on getting paid through mining blocks, the money might be in the data servers.


For the readers of this forum who don't really know, Quantum Computers calculate many equations (100+ equations) within one sitting...as to regular computers just calculate about 1 or 2 equations in one sitting. That is just the most basic method and comparing of the two.

With the speed of Quantum Computing the data will be enormous.

Just storing large amounts of data isn't enough though because of the size of Quantum Computing data is big -that big data will have to be transferred to the data servers at a very high speed without any issues. The internet speeds that most people and corporations have right now will most likely not be able to stay balanced with the speed to data ratio.




Then again..Who knows, Bitcoin might not even make it that far.