What is a quantum computer?

Quantum computer is a machine that can realize quantum computation. It is a system that can realize mathematical and logical operation, processing and storage of information through the laws of quantum mechanics. It takes quantum state as memory unit and information storage form, quantum communication and quantum computing based on quantum dynamics evolution as information transmission and processing, and the size of its hardware components in quantum computer reaches the order of atoms or molecules. 

Components of a quantum computer

Like many computers, quantum computer is composed of many hardware and software, including quantum algorithm, quantum coding, etc. In terms of hardware, it includes quantum transistor, quantum memory, quantum effector, etc.

Principle of quantum computer

Quantum computer is a device that USES quantum logic for general computation. Unlike electronic computers, quantum computing USES qubits to store data. It USES quantum algorithms to manipulate data. The principle of quantum computing actually has two parts. One part is the physics principle and realization of quantum computer. The other part is quantum algorithms. This paper explains the physics part by quoting the works of academician guo guangcan.

The following are cited articles:

A quantum bit can prepare a coherent superposition of 0 and 1 in two logical states, in other words, it can store both 0 and 1. Consider a N physical bits of memory, if it is a classic memory, it can only store 2 ^ N maybe anyone among the data, if it is a quantum memory, it can store the number 2 ^ N, at the same time and with the increase of N, its ability to store information index rose, for example, a 250 quantum bit memory (made up of 250 atoms) may be stored for up to 2 ^ 250, the number of all the atoms in the universe than existing known. Since mathematical operations can be performed on all the data in the memory at the same time, a quantum computer can perform mathematical operations on 2^N input Numbers simultaneously in a single operation. The effect is equivalent to a classic computer performing two to the NTH operations repeatedly, or parallel operations with two to the NTH different processors. Thus, quantum computers can save a lot of computing resources (such as time, memory units, etc.).

Two effective algorithms for quantum computing:

1.Shor algorithm: use the existing computer logarithm N (binary length l ogN) to do the factorization, the operation step (time) with the input length (l ogN) exponential growth.

2.Grover's algorithm: every query can check all 1 million Numbers at the same time. Since 1 million qubits are in a superposition state, the effect of quantum interference will affect the previous result to the next quantum operation. The operation generated by this interference is repeated 1000 times (that is, N √), and the probability of obtaining the correct answer is 1/2. But if you do it a few more times, the chances of finding the number you need are closer to 1.

Schematic diagram of quantum

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