Can new quantum computers mine bitcoin much faster than traditional ones?
The answer is yes, but a clear distinction must be made between theory and practice.
In fact, as Vitalik Buterin said a few months ago:
“My one-sentence impression of recent quantum supremacy stuff so far is that it is to real quantum computing what hydrogen bombs are to nuclear fusion. Proof that a phenomenon and the capability to extract power from it exist, but still far from directed use toward useful things”.
The computational power of quantum computers is theoretically much higher than that of normal computers. Not only are they more powerful because they are able to perform many more operations than traditional computers, in the same interval of time, but also because they work differently.
Indeed, the computing power of a quantum computer is potentially so much higher that the difference with traditional computers would be astronomical.
But this is only the theory, as to date, there is no evidence that quantum computers are actually usable for mining. The main problems, from a practical point of view, are the high operating costs, and the fact that quantum computers nowadays are still only prototypes that are not able to operate continuously at full capacity.
Therefore, this is not a problem of pressing concern. Quantum computers have been talked about for several years now since they were hypothesized in the now very distant 1980, and the first experiments were conducted in 2001.
However, it was only in 2019 that working prototypes were created that could be used for all purposes, so it will presumably take several more years before they can actually be used for mining.
The key point, however, is that with conventional computers it may still take another 120 years to mine all the bitcoins yet to be mined, and it is extremely likely that quantum computers suitable for mining will be on the market in this time.
The problems that quantum computers could cause to bitcoin mining are basically two:
- they could prevent traditional computers from mining,
- they could potentially extract in a few minutes all the bitcoins remaining.
With regard to the first problem, there is no solution, because traditional computers are not really able to compete with quantum computers. As time goes by, however, the revenue for the miners from the block rewards will be reduced to such a point that it may not be able to cover the costs. In fact, the operating costs of a quantum computer are very high, and in the future, it may not be profitable to mine bitcoins with quantum computers.
The second problem is related to the first because as long as mining with quantum computers is profitable it makes sense to imagine that someone could try to use them to mine all the remaining bitcoins very quickly, but when it won’t be profitable anymore then this scenario will also be less likely.
If, however, in the coming years it will be possible to actually use quantum computers to mine bitcoins, then the severity of this second problem will depend very much on their actual computing power.
A new Bitcoin halving in 2024
Let’s not forget that in 2024 there will be another halving, which will reduce the extracted bitcoins to 3.125 BTC per block and presumably in 2027 or 2028 there will be another one that will reduce it further to 1.5625 BTC.
As a result, if in 2024, for example, it will be possible to use quantum computers to mine bitcoins, there will only be about 1.3 million BTC left to extract, whereas if it will only be possible from 2028, there will only be a little more than 650,000 BTC left.
Many people doubt that in 2024, or even 2028, quantum computers that can actually be used to mine bitcoins will actually be available on the market, so the problem could occur even later.
For example, after the subsequent halving, presumably in 2031, only a little more than 300,000 BTC will remain to be mined, so the profitability of such an operation would already be much lower.
Furthermore, although a very powerful quantum computer could also be able to mine all the remaining bitcoins in a very short time, it must be taken into account that every 2,016 blocks the difficulty is updated and if a quantum computer could mine 2,016 blocks in a very short time, the difficulty would skyrocket, bringing the average time needed to mine a block close to 10 minutes.
Of course, such a scenario would be full of potentially negative consequences, especially if the quantum computer were to stop mining after the difficulty had skyrocketed, as it would be necessary to wait another 2,016 blocks to see it decrease.
However, given the relative slowness with which the development of this technology is proceeding, there are in fact years to find other solutions.