Constrained Variational Quantum Eigensolver: Quantum Computer Search Engine in the Fock Space.
Constrained Variational Quantum Eigensolver: Quantum Computer Search Engine in the Fock Space.
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DOI：
10.1021/acs.jctc.8b00943
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发表时间：
2018-06
影响因子：
5.5
通讯作者：
I. G. Ryabinkin;Scott N. Genin;A. Izmaylov
中科院分区：
文献类型：
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作者：
I. G. Ryabinkin;Scott N. Genin;A. Izmaylov
变分量子本征解算器（VQE）是一种有效的计算方法，有望在通用门量子计算机的电子结构计算中实现化学精确性。然而，像计算氢分子阳离子H2+的电子能量这样简单的任务对于一般的VQE协议是不可能的，因为计算总是会崩溃到相应的中性形式H2的较低能量。问题的起源是，VQE有效地执行一个无约束的能量优化的Fock空间的原始电子问题。我们将展示如何通过引入必要的约束，指导VQE对感兴趣的电子状态，可以避免这种情况。所提出的约束VQE可以找到具有一定数量的电子，一定的自旋或任何其他属性的电子状态。此外，新算法自然地去除了势能面（PES）中的非物理扭结，这些扭结经常出现在常规VQE中，并且需要大量额外的量子资源来去除它们。我们通过在Rigetti Computing Inc.上模拟H2和H2O的各种状态的PES来展示约束VQE的性能。的19 Q-Acorn量子处理器。
Variational quantum eigensolver (VQE) is an efficient computational method promising chemical accuracy in electronic structure calculations on a universal-gate quantum computer. However, such a simple task as computing the electronic energy of a hydrogen molecular cation, H2+, is not possible for a general VQE protocol because the calculation will invariably collapse to a lower energy of the corresponding neutral form, H2. The origin of the problem is that VQE effectively performs an unconstrained energy optimization in the Fock space of the original electronic problem. We show how this can be avoided by introducing necessary constraints directing VQE toward the electronic state of interest. The proposed constrained VQE can find an electronic state with a certain number of electrons, a certain spin, or any other property. Moreover, the new algorithm naturally removes unphysical kinks in potential energy surfaces (PESs), which frequently appeared in the regular VQE and required significant additional quantum resources for their removal. We demonstrate the performance of the constrained VQE by simulating PESs of various states of H2 and H2O on Rigetti Computing Inc.'s 19Q-Acorn quantum processor.