Synthesis of Approximate Parametric Circuits for Variational Quantum Algorithms

This work presents a novel approach to synthesize approximate circuits for the ansatze of variational quantum algorithms (VQA) and demonstrates its effectiveness in the context of solving integer linear programming (ILP) problems. Synthesis is generalized to produce parametric circuits in close approximation of the original circuit and to do so offline . This removes synthesis from the (online) critical path between repeated quantum circuit executions of VQA. We hypothesize that this approach will yield novel high fidelity results beyond those discovered by the baseline without synthesis. Simulation and real device experiments complement the baseline in finding correct results in many cases where the baseline fails to find any and do so with on average 32% fewer CNOTs in circuits.

1 Introduction

Variational quantum algorithms (VQAs) [11], [14] are a promising approach to solve relevant quantum chemistry [6], [14] and optimization problems algorithmically [4] on quantum computers. A VQA comprises a classical loop that repeatedly executes a parameterized quantum kernel alternating with classical optimization on the kernel's output to identify new parameters to consider.