Electronic excited states from a variance-based contracted quantum eigensolver

Physical review. A/Physical review, A, Год журнала: 2023, Номер 108(2)

Опубликована: Авг. 25, 2023

Electronic excited states of molecules are central to many physical and chemical processes, yet they typically more difficult compute than ground states. In this paper we leverage the advantages quantum computers develop an algorithm for highly accurate calculation We solve a contracted Schr\"odinger equation (CSE)---a contraction (projection) onto space two electrons---whose solutions correspond identically equation. While recent algorithms solving CSE, known as eigensolvers (CQEs), have focused on states, CQE based variance that is designed optimize rapidly or state. apply ${\mathrm{H}}_{2}, {\mathrm{H}}_{4}$, BH.

Язык: Английский

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Quantum benefit of the quantum equation of motion for the strongly coupled many-body problem

Physical review. C, Год журнала: 2024, Номер 109(1)

Опубликована: Янв. 2, 2024

We investigate the quantum equation of motion (qEOM), a hybrid quantum-classical algorithm for computing excitation properties fermionic many-body system, with particular emphasis on strong-coupling regime. The method is designed as stepping stone towards building more accurate solutions strongly coupled systems, such medium-heavy nuclei, using algorithms to surpass current barrier in classical computation. Approximations increasing accuracy exact solution Lipkin-Meshkov-Glick Hamiltonian $N=8$ particles are studied digital simulators and IBM devices. Improved achieved by applying operators growing complexity generate excitations above correlated ground state, which determined variational eigensolver. demonstrate explicitly that qEOM exhibits benefit due independence number required measurements from configuration complexity. Postprocessing examination shows device errors amplified coupling strength. A detailed error analysis presented, mitigation based zero noise extrapolation implemented.

Язык: Английский

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Subspace Methods for the Simulation of Molecular Response Properties on a Quantum Computer

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(9), С. 3729 - 3740

Опубликована: Май 1, 2024

We explore Davidson methods for obtaining excitation energies and other linear response properties within the recently developed quantum self-consistent (q-sc-LR) method. Davidson-type allow only a few selected without explicitly constructing electronic Hessian since they require ability to perform Hessian-vector multiplications. apply method calculate of hydrogen chains (up H10) analyze aspects statistical noise computing on simulators. Additionally, we such as static polarizabilities H2, LiH, H2O, OH–, NH3, show that unitary coupled cluster outperforms classical projected molecular systems with strong correlation. Finally, formulate damped (complex) response, application nitrogen K-edge X-ray absorption ammonia, C6 coefficients NH3.

Язык: Английский

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Measurement Optimization Techniques for Excited Electronic States in Near-Term Quantum Computing Algorithms

Journal of Chemical Theory and Computation, Год журнала: 2023, Номер 19(11), С. 3184 - 3193

Опубликована: Май 24, 2023

The variational quantum eigensolver (VQE) remains one of the most popular near-term algorithms for solving electronic structure problem. Yet, its practicality, main challenge to overcome is improving measurement efficiency. Numerous techniques have been developed recently, but it unclear how these state-of-the-art will perform in extensions VQE obtaining excited states. Assessing techniques' performance state crucial because requirements are typically much greater than ground VQE, as must measure expectation value multiple observables addition that Hamiltonian. Here, we adapt various two widely used algorithms: multistate contraction and subspace expansion. Then, each technique numerically compared. We find best methods ones utilizing Hamiltonian data wave function information minimize number measurements. In contrast, randomized more appropriate expansion, with many vastly different energy scales measure. Nevertheless, when possible algorithm considered, significantly fewer measurements required

Язык: Английский

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Quantum Davidson algorithm for excited states

Quantum Science and Technology, Год журнала: 2024, Номер 9(3), С. 035012 - 035012

Опубликована: Апрель 4, 2024

Abstract Excited state properties play a pivotal role in various chemical and physical phenomena, such as charge separation light emission. However, the primary focus of most existing quantum algorithms has been ground state, seen phase estimation variational eigensolver (VQE). Although VQE-type methods have extended to explore excited states, these grapple with optimization challenges. In contrast, Krylov subspace (QKS) method introduced address both positioning itself cost-effective alternative estimation. conventional QKS methodologies depend on pre-generated through real or imaginary-time evolutions. This is inherently expansive can be plagued issues like slow convergence numerical instabilities, often leading relatively deep circuits. Our research presents an economic algorithm, which we term Davidson (QDavidson) algorithm. innovation hinges iterative expansion incorporation pre-conditioner within framework. By using residues eigenstates expand subspace, manage formulate compact that aligns closely exact solutions. paves way for more rapid comparison other techniques, Lanczos. Using simulators, employ novel QDavidson algorithm delve into systems, spanning from Heisenberg spin model molecules. Compared methods, not only converges swiftly but also demands significantly shallower circuit. efficiency establishes pragmatic tool elucidating computing platforms.

Язык: Английский

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Nonadiabatic Molecular Dynamics with Fermionic Subspace-Expansion Algorithms on Quantum Computers

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(14), С. 5951 - 5963

Опубликована: Июль 5, 2024

We introduce a novel computational framework for excited-state molecular quantum dynamics simulations driven by quantum-computing-based electronic-structure calculations. This leverages the fewest-switches surface-hopping method simulating nuclear and calculates required transition properties with different flavors of subspace expansion equation-of-motion algorithms. apply our to simulate collision reaction between hydrogen atom molecule. For this system, we critically compare accuracy efficiency algorithms show that only methods can capture both weak strong electron correlation effects properly describe nonadiabatic tune reactive event.

Язык: Английский

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Exploring Parameter Redundancy in the Unitary Coupled-Cluster Ansätze for Hybrid Variational Quantum Computing

The Journal of Physical Chemistry A, Год журнала: 2023, Номер 127(20), С. 4526 - 4537

Опубликована: Май 16, 2023

One of the commonly used chemically inspired approaches in variational quantum computing is unitary coupled-cluster (UCC) ansätze. Despite being a systematic way approaching exact limit, number parameters standard UCC ansätze exhibits unfavorable scaling with respect to system size, hindering its practical use on near-term devices. Efforts have been taken propose some variants better scaling. In this paper, we explore parameter redundancy preparation singles and doubles (UCCSD) employing spin-adapted formulation, small amplitude filtration, entropy-based orbital selection approaches. Numerical results using our approach molecules exhibited significant cost reduction be optimized time convergence compared conventional UCCSD-VQE simulations. We also discuss potential application machine learning techniques further exploring redundancy, providing possible direction for future studies.

Язык: Английский

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Simulating Vibronic Spectra by Direct Application of Doktorov Formulas on a Superconducting Quantum Simulator

The Journal of Physical Chemistry A, Год журнала: 2024, Номер 128(21), С. 4369 - 4377

Опубликована: Май 16, 2024

In this work, a direct quantum implementation of the Doktorov formulas for calculating vibronic spectrum molecules under harmonic approximation is presented. It applied to three-atom H2O, SO2, ClO2, HS2, and ZnOH. The method solves classically hard problem estimating Franck–Condon (FC) factors by using Duschinsky matrices as only input via circuit. This has advantage avoiding basis changes, artificial squeezing parameters, symmetry dependencies. other words, it general that can easily be generalized bigger molecules. results are compared with algorithms classical anharmonic algorithms. Furthermore, circuit requirements studied in order estimate its applicability on real superconducting hardware.

Язык: Английский

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Quantum computing and chemistry

Cell Reports Physical Science, Год журнала: 2024, Номер 5(9), С. 102105 - 102105

Опубликована: Июль 15, 2024

As the year-to-year gains in speeds of classical computers continue to taper off, computational chemists are increasingly examining quantum computing as a possible route achieve greater performance. Quantum computers, built upon properties superposition, interference, and entanglement bits, offer, principle, possibility outperform for solving many important classes problems. In field chemistry, algorithm development offers promising propositions classically intractable problems areas such electronic structure, chemical dynamics, spectroscopy, cheminformatics. However, physical implementations still their infancy have yet useful computations. Still, software chemistry is highly active area research. this perspective, we summarize recent progress algorithms, hardware, software, describe challenges that remain applications.

Язык: Английский

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Self-consistent Quantum Linear Response with a Polarizable Embedding Environment

The Journal of Physical Chemistry A, Год журнала: 2025, Номер unknown

Опубликована: Янв. 23, 2025

Quantum computing presents a promising avenue for solving complex problems, particularly in quantum chemistry, where it could accelerate the computation of molecular properties and excited states. This work focuses on excitation energies with hybrid quantum-classical algorithms near-term devices, combining linear response (qLR) method polarizable embedding (PE) environment. We employ self-consistent operator manifold (q-sc-LR) top unitary coupled cluster (UCC) wave function combination Davidson solver. The latter removes need to construct entire electronic Hessian, improving computational efficiency when going toward larger molecules. introduce new superposition-state-based technique compute Hessian-vector products show that this approach is more resilient noise than our earlier gradient-based approach. demonstrate performance PE-UCCSD model systems such as butadiene para-nitroaniline water find delivers comparable accuracy classical PE-CCSD methods simple closed-shell systems. also explore challenges posed by hardware propose error mitigation techniques maintain accurate results noisy computers.

Язык: Английский

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