On December 4, 2020, the University of Science and Technology of China officially announced that it had created the world-class quantum computer prototype "Nine Chapters". So far, China has become the second country in the world to have a quantum computer. Jiuzhang computer only needs a few hundred seconds to calculate the Bose sampling problem, while the same problem requires a supercomputer to calculate billions of years. If quantum computers are used to mine, will all Bitcoins be mined in a very short time? Many people think that once the technology of quantum computers matures, the Bitcoin system will collapse. Similarly, if quantum computers are used to crack Bitcoin wallets, our encrypted assets will also be looted by hackers in an instant. At present, the computing power of electronic computers is like the gap between a drop of water and the Pacific Ocean in front of quantum computers. Therefore, based on the above, we seem to understand why many people have a pessimistic attitude towards the encryption field.

So are quantum computers really the end of cryptoassets? First, let's understand what a quantum computer is. A quantum computer (quantum computer) is a device that uses quantum logic for general-purpose computing. Quantum states are used as calculation units. At present, quantum computers use physical systems such as atoms, ions, and photons. Different types of quantum computers use They are different particles. Unlike electronic computers, the object of quantum computing to store data is qubits. It uses quantum algorithms to perform data operations. Its biggest feature is its fast calculation speed. Use such a fast quantum computer to mine Mining means a huge amount of computing power. Is it possible to mine all the cryptocurrencies in an instant? The answer is: no! Let’s analyze it from a technical point of view.

There are two main encryption algorithms used by Bitcoin: elliptic curve cryptography and sha256 hash algorithm. Among them, the elliptic curve digital signature algorithm is mainly used for the generation of public key and private key, and the sha256 hash algorithm is mainly used for generating wallet address with public key and proof of work (POW) during mining. The address of the wallet is to convert an input into another output in an irreversible way. It has a very strong one-way, so it is completely impossible to deduce the input from the output.

So can quantum computers be used to increase the speed of mining? The protocol of the Bitcoin system stipulates that the computing power will increase with the number of calculations, and it will increase until an average of every 10 minutes can be counted as a success. The process of mining Bitcoin is to execute the operation process of sha256 continuously. The public key of Bitcoin and the corresponding address are encrypted by sha256. This algorithm is theoretically impossible for quantum computers, and there is no such algorithm yet. The algorithm that can crack sha256. Even if the quantum computer technology really matures one day in the future, because it touches the common interests of all Bitcoin holders, it will be natural to carry out fork upgrades through the consensus mechanism at that time.

We can see above that, at least according to the existing technology, quantum computers will not pose a threat to cryptocurrencies, and will even promote the development of the blockchain industry. At present, most of the research on quantum computers in the world is aimed at a specific problem. For example, the "Nine Chapters" quantum computer is designed to solve the problem of wave-color sampling. If a quantum computer is to be specially manufactured for the Bitcoin algorithm, the research and development costs It is quite expensive. From the perspective of the input-output ratio, perhaps this "business" is not cost-effective.