Quantum computers can exploit a Hilbert space whose dimension increases exponentially with the number of qubits. In experiment, quantum supremacy has recently been achieved by the Google team by using a noisy intermediate-scale quantum (NISQ) device with over 50 qubits. However, the question of what can be implemented on NISQ devices is still not fully explored, and discovering useful tasks for such devices is a topic of considerable interest. Hybrid quantum-classical algorithms are regarded as well-suited for execution on NISQ devices by combining quantum computers with classical computers, and are expected to be the first useful applications for quantum computing. Meanwhile, mitigation of errors on quantum processors is also crucial to obtain reliable results. In this article, we review the basic results for hybrid quantum-classical algorithms and quantum error mitigation techniques. Since quantum computing with NISQ devices is an actively developing field, we expect this review to be a useful basis for future studies.

中文翻译：

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混合量子经典算法和量子误差缓解

量子计算机可以利用希尔伯特空间，其空间随着量子位的数量呈指数增长。在实验中，谷歌团队最近通过使用具有超过50量子比特的高噪声中尺度量子（NISQ）设备实现了量子霸权。但是，关于在NISQ设备上可以实现什么的问题仍未得到充分探讨，而为此类设备发现有用的任务是一个令人关注的话题。通过将量子计算机与经典计算机结合，混合量子经典算法被认为非常适合在NISQ设备上执行，并且有望成为量子计算的第一个有用的应用程序。同时，减轻量子处理器上的错误对于获得可靠的结果也至关重要。在这篇文章中，我们回顾了混合量子经典算法和量子误差缓解技术的基本结果。由于使用NISQ设备进行量子计算是一个活跃的领域，因此我们希望这次审查将为将来的研究提供有用的基础。