Variational quantum eigensolver simulations with the multireference unitary coupled cluster ansatz: a case study of the C2v quasi-reaction pathway of beryllium insertion into a H2 molecule

Sugisaki, Kenji; Kato, Takumi; Minato, Yuichiro; Okuwaki, Koji; Mochizuki, Yuji

doi:10.1039/d1cp04318h

Cited by 16 publications

(15 citation statements)

References 109 publications

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“…For an overview of applications to chemistry, see reviews [116][117][118] and specific applications [45,72,73,114,[119][120][121][122][123][124][125][126][127][128][129][130][131].…”

Section: Vqe Applied To Chemistrymentioning

confidence: 99%

Quantum information processing with superconducting circuits: a perspective

Wendin¹

2023

Preprint

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The last five years have seen a dramatic evolution of platforms for quantum computing, taking the field from physics experiments to quantum hardware and software engineering. Nevertheless, despite this progress of quantum processors, the field is still in the noisy intermediate-scale quantum (NISQ) regime, seriously limiting the performance of software applications. Key issues involve how to achieve quantum advantage in useful applications for quantum optimization and materials science, connected to the concept of quantum supremacy first demonstrated by Google in 2019. In this article we will describe recent work to establish relevant benchmarks for quantum supremacy and quantum advantage, present recent work on applications of variational quantum algorithms for optimization and electronic structure determination, discuss how to achieve practical quantum advantage, and finally outline current work and ideas about how to scale up to competitive quantum systems.

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“…For an overview of applications to chemistry, see reviews [116][117][118] and specific applications [45,72,73,114,[119][120][121][122][123][124][125][126][127][128][129][130][131].…”

Section: Vqe Applied To Chemistrymentioning

confidence: 99%

Quantum information processing with superconducting circuits: a perspective

Wendin¹

2023

Preprint

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“…5) and describing classically how the choice of the basis set affects the ground state energy (Section 2). The second strategy will be to relax (optimize) the active space through a classical CASSCF calculation 21 to see how the basis set affects the ground state energy (Section 3). Finally, the third approach will be a hybrid quantum CASSCF similar to the one proposed by Tilly et al 22 where the orbital optimization will be done by dividing tasks between classical and quantum backends (Section 4).…”

Section: Introductionmentioning

confidence: 99%

“…To increase the correlation in the active space and improve the accuracy of the quantum simulation, one can bring more correlated orbitals into the molecular Hamiltonian. This strategy has been adopted before by Sugisaki et al 21 to study the insertion of beryllium into H 2 but, in our case, we are interested in the trend of the correlation with the basis set size.…”

Section: Introductionmentioning

confidence: 99%

Complete active space methods for NISQ devices: The importance of canonical orbital optimization for accuracy and noise resilience

Triviño

Delcey

Wendin

2023

Preprint

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To break the scaling of the number of qubits with the size of the basis set, one can divide the molecular space into active and inactive, also known as complete active space methods. Nevertheless, more than the active space selection is needed for accuracy and effectively describing quantum mechanical effects as correlation. This study highlights the importance of optimizing the active space orbitals to describe correlation and improve the Hartree-Fock energies. We will explore orbital optimization classically and through quantum computation and how, theoretically, a chemically inspired ansatz as the UCCSD compares with a classical full CI (FCI) description of the active space in weakly and strongly correlated molecules. Finally, we will explore the practical implementation of a quantum CASSCF where hardware-efficient circuits need to be used, and noise hinders its accuracy and convergence. Moreover, we explore canonical and non-canonical active orbitals and how those influence the convergence of the quantum CASSCF routine in the presence of noise.

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“…In general, a highly parametrized ansätz leads to higher expressibility, but also suffers from high circuit depth and trainability [29]. Other notable works in this direction include: Qubit Coupled Cluster (QCC) [30], Orbital Optimized Unitary Coupled Cluster (OO‐UCC) [31, 32], Double Unitary Coupled Cluster (DUCC) [33, 34], Adaptive Derivative‐Assembled Pseudo‐Trotter Variational Quantum Eigensolver (ADAPT‐VQE) [35], MR‐UCCpGSD [36] and the Projective Quantum Eigensolver (PQE) [37] approaches.…”

Section: Introductionmentioning

confidence: 99%

Iterative quantum phase estimation with variationally prepared reference state

Halder

Prasannaa²,

Agarawal

et al. 2022

Int J of Quantum Chemistry

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The iterative quantum phase estimation algorithm (IQPE) is theoretically appealing in its wide scope of being able to handle electronic correlation. However, the quality of the initial input state strongly enhances the probability of landing on the desired eigenstate. In this work, we systematically study two different parametrization schemes of the unitary coupled cluster (UCC) ansätz in the variational quantum eigensolver (VQE) framework toward the reference state preparation for IQPE. The efficacy of the UCC variants toward an appropriate state preparation is studied with prototypical H4 molecule on a circle. While the conventional UCC ansätz can lead to high success probability across various degrees of electronic complexity, a resource efficient minimally parametrized UCC ansätz consisting of active space excitations is shown to incorporate the essential static correlation in the reference state description. We demonstrate that such a carefully prepared initial state can significantly reduce the effects of noise due to sampling in the estimation of the desired eigenphase.

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Variational quantum eigensolver simulations with the multireference unitary coupled cluster ansatz: a case study of the C_2v quasi-reaction pathway of beryllium insertion into a H₂ molecule

Abstract: Variational quantum eigensolver (VQE)-based quantum chemical calculations have been extensively studied as a computational model using noisy intermediate-scale quantum devices. VQE uses a parametrized quantum circuit defined through an “ansatz”...

Cited by 16 publications

References 109 publications

Quantum information processing with superconducting circuits: a perspective

Quantum information processing with superconducting circuits: a perspective

Complete active space methods for NISQ devices: The importance of canonical orbital optimization for accuracy and noise resilience

Iterative quantum phase estimation with variationally prepared reference state

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