论文标题
差异相估计与变异快速转发
Variational Phase Estimation with Variational Fast Forwarding
论文作者
论文摘要
子空间对角线化方法最近以经典的对角度化小矩阵来访问基态和一些分子汉密尔顿分子的激发状态的有前途的手段，其元素可以通过量子计算机有效地获得。最近提出的变异量子相估计（VQPE）算法使用实时进化状态的基础，可以直接从单位矩阵U = exp（-iht）中直接获得能量特征值，可以用使用的态数在使用的状态数量中以成本线性计算。在本文中，我们报告了用于任意分子系统的VQPE的基于电路的实现，并评估其H2，H3+和H6分子的性能和成本。我们还建议使用各种快速转发（VFF）降低到vQPE的时间进化电路的量子深度。我们表明，即使对真实时间进化的状态的忠诚度很低，近似值也为哈密顿对角线化提供了良好的基础。在高保真情况下，我们表明近似统一的U可以对角度化，从而保留了精确VQPE的线性成本。
Subspace diagonalisation methods have appeared recently as promising means to access the ground state and some excited states of molecular Hamiltonians by classically diagonalising small matrices, whose elements can be efficiently obtained by a quantum computer. The recently proposed Variational Quantum Phase Estimation (VQPE) algorithm uses a basis of real time-evolved states, for which the energy eigenvalues can be obtained directly from the unitary matrix U = exp(-iHt), which can be computed with cost linear in the number of states used. In this paper, we report a circuit-based implementation of VQPE for arbitrary molecular systems and assess its performance and costs for the H2, H3+ and H6 molecules. We also propose using Variational Fast Forwarding (VFF) to decrease to quantum depth of time-evolution circuits for use in VQPE. We show that the approximation provides a good basis for Hamiltonian diagonalisation even when its fidelity to the true time evolved states is low. In the high fidelity case, we show that the approximate unitary U can be diagonalised instead, preserving the linear cost of exact VQPE.
