摘要
The original variational quantum eigensolver(VQE)typically minimizes energy with hybrid quantum-classical optimization that aims to find the ground state.Here,we propose a VQE based on minimizing energy variance and call it the variance-VQE,which treats the ground state and excited states on the same footing,since an arbitrary eigenstate for a Hamiltonian should have zero energy variance.We demonstrate the properties of the variance-VQE for solving a set of excited states in quantum chemistry problems.Remarkably,we show that optimization of a combination of energy and variance may be more efficient to find low-energy excited states than those of minimizing energy or variance alone.We further reveal that the optimization can be boosted with stochastic gradient descent by Hamiltonian sampling,which uses only a few terms of the Hamiltonian and thus significantly reduces the quantum resource for evaluating variance and its gradients.
作者
张旦波
陈彬琳
原展豪
殷涛
Dan-Bo Zhang;Bin-Lin Chen;Zhan-Hao Yuan;Tao Yin(Guangdong-Hong Kong Joint Laboratory of Quantum Matter,Frontier Research Institute for Physics,South China Normal University,Guangzhou 510006,China;Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials,School of Physics and Telecommunication Engineering,South China Normal University,Guangzhou 510006,China;Guangzhou Educational Infrastructure and Equipment Center,Guangzhou 510006,China;Yuntao Quantum Technologies,Shenzhen 518000,China)
基金
supported by the National Natural Science Foundation of China(Grant No.12005065)
the Guangdong Basic and Applied Basic Research Fund(Grant No.2021A1515010317)