论文标题
用本地偏见的古典阴影测量量子哈密顿量
Measurements of Quantum Hamiltonians with Locally-Biased Classical Shadows
论文作者
论文摘要
获得量子可观察物的精确估计是变异量子算法的关键步骤。我们考虑在量子计算机上准备的状态获得的分子哈密顿量的期望值的问题。我们为此任务提出了一个新颖的估计器，该估计量通过对哈密顿量的知识以及对基础量子状态的经典近似进行了局部优化。我们的估计器基于量子状态的经典阴影的概念，并且具有不增加电路深度的重要特性。我们对大小增加的分子哈密顿量测试其性能，发现相对于当前未增加电路深度的当前测量方案的方差降低。
Obtaining precise estimates of quantum observables is a crucial step of variational quantum algorithms. We consider the problem of estimating expectation values of molecular Hamiltonians, obtained on states prepared on a quantum computer. We propose a novel estimator for this task, which is locally optimised with knowledge of the Hamiltonian and a classical approximation to the underlying quantum state. Our estimator is based on the concept of classical shadows of a quantum state, and has the important property of not adding to the circuit depth for the state preparation. We test its performance numerically for molecular Hamiltonians of increasing size, finding a sizable reduction in variance with respect to current measurement protocols that do not increase circuit depths.
