'Error correction and detection in variational quantum algorithms'

“量子计算机提供了超越经典算法的计算速度的诱人可能性。然而，现有量子器件的低质量意味着量子电路大到足以实现这种可能性，但由于噪声而损坏。变分量子算法（VQA）是一种混合的经典量子方法，旨在对这种噪声具有更强的鲁棒性，因此在短期内有望成为量子优势的候选者。我博士的目标是在目前可用的设备上使用vqa来实现量子优势。这将通过研究以下主题来完成：(1)电路重新编译，(2)荒芜高原问题和(3)“智能”量子算法。第一年的研究将为实现这一目标奠定基础。对于主题(1)，我将研究如何减少量子电路中的门的数量，同时保持其对VQA给定输入状态的影响。对于主题(2)，我将调查设备噪声可能导致荒芜高原的程度，并制定策略来减轻对经典优化过程的影响。(3)的总体思路是开发对噪声具有固有鲁棒性的算法，我对该主题的特定起点将是虚时间进化。第一年建立的知识库将成为开发vqa有效策略的基础，这些策略i)对噪声具有鲁棒性ii)针对现有量子器件进行了优化。这些技术将与减少实验噪声的技术一起使用，这将使IBM尖端的量子设备得到充分利用。”

'Quantum computers offer the tantalising possibility of a computational speedup over classical algorithms. However, the low quality of existing quantum devices means quantum circuits large enough to realise this possibility are corrupted due to noise. Variational quantum algorithms (VQA) are a hybrid classical-quantum approach intended to be more robust to this noise and as such are a promising candidate for a quantum advantage in the near term. The goal for my PhD is to achieve a quantum advantage using VQAs on currently available devices. This will be done by investigating the following topics: (1) circuit recompilation, (2) the barren plateau problem and (3) 'smart' quantum algorithms.The first year of research will set the stage for this goal. For topic (1) I will examine how the number of gates in a quantum circuit can be reduced while maintaining its effect on a given input state to a VQA. For topic (2) I will investigate the extentto which device noise can cause barren plateaus and develop strategies to mitigate the effect on the classical optimisation procedure. The general idea for (3) is to develop algorithms which are inherently robust to noise, my particular starting point for the topic will be imaginary time evolution.The knowledge base built during this first year will be the foundation for developing effective strategies for VQAs which are i) robust to noise ii) optimised for existing quantum devices. These will be used alongside techniques for mitigating experimentalnoise which will allow cutting edge IBM quantum devices to be fully utilised.'