Understanding the capabilities of classical simulation methods is key to identifying where quantum computers are advantageous. Not only does this ensure that quantum computers are used only where necessary, but also one can potentially identify subroutines that can be offloaded onto a classical device. In this work, we show that it is always possible to generate a classical surrogate of a sub-region (dubbed a "patch") of an expectation landscape produced by a parameterized quantum circuit. That is, we provide a quantum-enhanced classical algorithm which, after simple measurements on a quantum device, allows one to classically simulate approximate expectation values of a subregion of a landscape. We provide time and sample complexity guarantees for a range of families of circuits of interest, and further numerically demonstrate our simulation algorithms on an exactly verifiable simulation of a Hamiltonian variational ansatz and long-time dynamics simulation on a 127-qubit heavy-hex topology.

本研究解决了经典仿真方法在量子计算机中的应用有限性的问题。我们提出了一种量子增强的经典算法，可以生成一个量子电路产生的期望景观子区域（称为“片段”）的经典代理，从而高效模拟相关的近似期望值。此外，我们为多种电路族提供了时间和样本复杂度保证，并在127量子位重六角拓扑的哈密顿量变分法的仿真上进行了数值验证。

高效的量子增强经典仿真用于量子景观的片段