Expert successfully suppresses quantum decoherence for quantum computer development apart from obstacles

[Guide] Researchers at the University of Southern California have successfully suppressed quantum decoherence by strong magnetic fields, removing a major obstacle to the development of the http://www.aliyun.com/zixun/aggregation/13408.html "> Quantum computer.

Researchers at the University of Southern California have successfully suppressed quantum decoherence (i.e., the disappearance of quantum coherence) through strong magnetic fields, removing a major obstacle to the development of quantum computers, according to a recent report by the US physicist organization network. The paper is published on the website of the journal Nature.

Traditional computers use traditional bits in their operations, the traditional bits represent 1 or 0 at a given time, while the quantum bits used by quantum computers can present multiple states at the same time-either 1 or 0-a state called quantum superposition, a manifestation of quantum coherence. The quantum computer's ability to perform complex computations beyond the reach of traditional computers is largely due to its use of this unique quantum effect. However, qubit is not an isolated system, it is very easy to interact with the external environment, causing the energy dissipation or relative phase change of the quantum bit, and eventually causing the quantum bit to degenerate into a mixed state or a single state by the coherent superposition state. This phenomenon is called quantum decoherence or decoherence.

Although Quantum decoherence is only a noise or interference, it is enough to destroy the unique function of a quantum computer. Therefore, quantum decoherence is also seen as a big "Bug" in quantum computers (computer vulnerabilities). In order to overcome the decoherence, the scientists have tried the method of quantum error correcting code and quantum avoiding error code, although the applicability is good, but the efficiency is not ideal.

Quantum decoherence in quantum bit systems can be divided into two categories. One is caused by an intrinsic characteristic of a quantum system; an external element of the system, such as impurities or defects in the material.

In a new study, Gao, an associate professor at the University of Southern California and his colleagues, studied a single molecule magnet to find ways to suppress the phenomenon of quantum decoherence. Single molecule magnets are chosen because of their high purity, which can eliminate the decoherence caused by external causes, so that researchers can accurately calculate the decoherence caused by internal causes. At the same time, the use of single molecule magnets allows researchers to create qubits from multiple quantum particles rather than a single quantum object. This is also the most common use of a quantum computer to build the way. At the same time, this method can greatly increase the signal of qubits, which makes it easier to detect these signals in a single molecule magnet.

In the experiment, the researchers tested the quantum decoherence phenomena in different environment (temperature, magnetic field, radiation, etc.) and found that the environmental factors had great influence on the quantum decoherence. The use of strong magnetic field can reduce the ambient noise level and effectively restrain the quantum decoherence phenomenon.

Fille Stamp, a professor of physics and astronomy in British Columbia, said it was a welcome achievement, and it first predicted and controlled the quantum decoherence in a complex system.

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