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通用量子计算机和容错量子计算——概念、现状和展望

Universal quantum computer and fault-tolerant quantum computation——concepts, status and prospects

  • 摘要: 量子计算技术近年来快速发展并受到广泛关注。文章将介绍一些量子计算的基本概念、现状以及远期和近期的主要挑战,使读者可以更准确地理解一些新近的进展,避免误解。通用量子计算机的主要应用之一是破解 RSA密码。没有量子纠错,我们很难实现密码破解规模的量子计算。因此,量子计算技术的一大挑战是如何实现有量子纠错保护的量子计算,也就是容错量子计算。通过介绍现有的实验技术,将发现目前已经可以在实验中实现错误率低于容错阈值的量子门,但容错量子计算离实际应用还有距离。主要的困难在于,量子容错需要数量巨大的低错误率的量子比特,超出了现有技术能达到的水平,需要进一步的发展。有噪声中等规模量子计算有可能在近期内成为现实,目前仍有一些理论和技术方面的瓶颈问题需要深入研究。在看到量子计算技术巨大潜在价值和长足进步的同时,有必要了解有哪些亟需解决的问题,直面关键、攻坚克难。

     

    Abstract: Quantum computing technology has developed rapidly in recent years and received wide attention. In this article, we review some basic concepts, current status, long-term and near-term challenges of quantum computing, so that readers can more accurately understand some recent progress and avoid misunderstanding. One of the main applications of universal quantum computers is to break RSA cryptographic systems. Without quantum error correction, it is difficult to achieve quantum computing in the scale of code breaking. Therefore, a primary challenge of quantum computing technology is to implement quantum computing protected by the quantum error correction, i.e. fault-tolerant quantum computation. By looking at the existing experimental technologies, we will find that quantum gates with error rates lower than the fault-tolerance threshold have been realised in experiments, but fault-tolerant quantum computation is still far from practical applications. The main difficulty is that quantum fault tolerance requires an enormous number of qubits with low error rates, beyond what can be achieved by state-of-the-art technologies; therefore, further development is needed. Noisy intermediate-scale quantum computation is likely to be realised in the near future, and there are still some theoretical and technical bottlenecks that need to be addressed. While we can see the huge potential value of quantum computing and recent significant progress, it is important to acknowledge the challenges, face the key problems, and overcome difficulties.

     

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