Quantum computer is a physical device that follows the laws of quantum mechanics, performs high-speed mathematical and logical operations, and stores and processes quantum information. When a device processes and calculates quantum information and runs quantum algorithms, it is a quantum computer. The concept of quantum computer comes from the research of reversible computer. The purpose of studying reversible computers is to solve the energy consumption problem of computers.

Whether it is quantum parallel computing or quantum analog computing, quantum coherence is essentially used. Unfortunately, it is difficult to maintain quantum coherence in practical systems. In the quantum computer, the qubit is not an isolated system, it will interact with the external environment, leading to the attenuation of quantum coherence, that is, decoherence.

Therefore, to make quantum computing a reality, a core problem is to overcome decoherence. Quantum coding is the most effective method to overcome decoherence. The main quantum coding schemes are: quantum error correction code, quantum error avoidance code and quantum error prevention code. Quantum error-correcting code is an analogy of classical error-correcting code, and it is the most studied code at present. Its advantage is wide application range, but its disadvantage is low efficiency.

Quantum computer is a physical device that follows the laws of quantum mechanics, performs high-speed mathematical and logical operations, and stores and processes quantum information. When a device processes and calculates quantum information and runs quantum algorithms, it is a quantum computer. The concept of quantum computer comes from the research of reversible computer. The purpose of studying reversible computers is to solve the energy consumption problem of computers.