'Error correction and detection in variational quantum algorithms'

'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 extent
to 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 experimental
noise which will allow cutting edge IBM quantum devices to be fully utilised.'