Quantum Equation of Motion with Orbital Optimization for Computing Molecular Properties in Near-Term Quantum Computing

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(9), P. 3613 - 3625

Published: May 3, 2024

Determining the properties of molecules and materials is one premier applications quantum computing. A major question in field how to use imperfect near-term computers solve problems practical value. Inspired by recently developed variants counterpart equation-of-motion (qEOM) approach orbital-optimized variational eigensolver (oo-VQE), we present a algorithm (oo-VQE-qEOM) for calculation molecular computing expectation values on computer. We perform noise-free simulations BeH2 series STO-3G/6-31G/6-31G* basis sets H4 H2O 6-31G using an active space four electrons spatial orbitals (8 qubits) evaluate excitation energies, electronic absorption, and, twisted H4, circular dichroism spectra. demonstrate that proposed can reproduce results conventional classical CASSCF calculations these systems.

Language: Английский

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Which Options Exist for NISQ-Friendly Linear Response Formulations?

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(9), P. 3551 - 3565

Published: April 25, 2024

Linear response (LR) theory is a powerful tool in classic quantum chemistry crucial to understanding photoinduced processes and biology. However, performing simulations for large systems the case of strong electron correlation remains challenging. Quantum computers are poised facilitate simulation such systems, recently, linear formulation (qLR) was introduced [Kumar et al., J. Chem. Theory Comput. 2023, 19, 9136–9150]. To apply qLR near-term beyond minimal basis set, we here introduce resource-efficient theory, using truncated active-space version multiconfigurational self-consistent field LR ansatz. Therein, investigate eight different formalisms that utilize novel operator transformations allow equations be performed on hardware. Simulating excited state potential energy curves absorption spectra various test cases, identify two promising candidates, dubbed "proj LRSD" "all-proj LRSD".

Language: Английский

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Understanding and mitigating noise in molecular quantum linear response for spectroscopic properties on quantum computers

Chemical Science, Journal Year: 2025, Volume and Issue: 16(10), P. 4456 - 4468

Published: Jan. 1, 2025

The promise of quantum computing to circumvent the exponential scaling chemistry has sparked a race develop algorithms for architecture. However, most works neglect quantum-inherent shot noise, let alone effect current noisy devices. Here, we present comprehensive study linear response (qLR) theory obtaining spectroscopic properties on simulated fault-tolerant computers and present-day near-term hardware. This work introduces novel metrics analyze predict origins noise in algorithm, proposes an Ansatz-based error mitigation technique, reveals significant impact Pauli saving reducing measurement costs subspace methods. Our hardware results using up cc-pVTZ basis set serve as proof principle absorption spectra general approach with accuracy classical multi-configurational Importantly, our exemplify that substantial improvements rates speed are necessary lift computational from concept actual field.

Language: Английский

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Characterizing Conical Intersections of Nucleobases on Quantum Computers

Journal of Chemical Theory and Computation, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 28, 2025

Hybrid quantum-classical computing algorithms offer significant potential for accelerating the calculation of electronic structure strongly correlated molecules. In this work, we present first quantum simulation conical intersections (CIs) in a biomolecule, cytosine, using superconducting computer. We apply contracted eigensolver (CQE)─with comparisons to conventional variational deflation (VQD)─to compute near-degenerate ground and excited states associated with intersection, key feature governing photostability DNA RNA. The CQE is based on an exact ansatz many-electron molecules absence noise─a critically important property resolving at CIs. Both methods demonstrate promising accuracy when compared diagonalization, even noisy intermediate-scale computers, highlighting their advancing understanding photochemical photobiological processes. ability simulate these critical our knowledge biological processes like repair mutation, implications molecular biology medical research.

Language: Английский

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Spin-Flip Unitary Coupled Cluster Method: Toward Accurate Description of Strong Electron Correlation on Quantum Computers

The Journal of Physical Chemistry Letters, Journal Year: 2023, Volume and Issue: 14(35), P. 7876 - 7882

Published: Aug. 28, 2023

Quantum computers have emerged as a promising platform to simulate strong electron correlation that is crucial catalysis and photochemistry. However, owing the choice of trial wave function employed in variational quantum eigensolver (VQE) algorithm, accurate simulation restricted certain classes correlated phenomena. Herein, we combine spin-flip (SF) formalism with unitary coupled cluster singles doubles (UCCSD) method via equation-of-motion (qEOM) approach allow for an efficient large family strongly problems. We show developed qEOM-SF-UCCSD/VQE outperforms its UCCSD/VQE counterpart cis-trans isomerization ethylene, automerization cyclobutadiene predicted barrier heights are good agreement experimentally determined values. The developments presented herein will further stimulate investigation this simulations other types correlated/entangled phenomena on computers.

Language: Английский

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

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(9), P. 3729 - 3740

Published: May 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.

Language: Английский

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Electronic excited states from a variance-based contracted quantum eigensolver

Physical review. A/Physical review, A, Journal Year: 2023, Volume and Issue: 108(2)

Published: Aug. 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.

Language: Английский

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

Journal of Chemical Theory and Computation, Journal Year: 2024, Volume and Issue: 20(14), P. 5951 - 5963

Published: July 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.

Language: Английский

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Self-consistent Quantum Linear Response with a Polarizable Embedding Environment

The Journal of Physical Chemistry A, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 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.

Language: Английский

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Equation-of-motion internally contracted multireference unitary coupled-cluster theory

The Journal of Chemical Physics, Journal Year: 2025, Volume and Issue: 162(15)

Published: April 16, 2025

The accurate computation of excited states remains a challenge in electronic structure theory, especially for systems with ground state that requires multireference treatment. In this work, we introduce novel equation-of-motion (EOM) extension the internally contracted unitary coupled-cluster framework (ic-MRUCC), termed EOM-ic-MRUCC. EOM-ic-MRUCC follows transform-then-diagonalize approach, analogy to its non-unitary counterpart [Datta and Nooijen, J. Chem. Phys. 137, 204107 (2012)]. By employing projective approach optimize state, method retains additive separability proper scaling system size. We show excitation energies are size-intensive if EOM operator satisfies “killer” conditions. Furthermore, propose represent changes reference upon electron via projected many-body operators span active orbitals equations formulated way invariant respect orbital rotations. test truncated single double excitations by computing potential energy curves several BeH2 model system, HF molecule, water undergoing symmetric dissociation. Across these systems, our delivers within 5 mEh (∼0.14 eV) from full configuration interaction. find truncating Baker–Campbell–Hausdorff series fourfold commutators contributes negligible errors (on order 10−5Eh or less), offering practical route highly excited-state calculations reduced computational overhead.

Language: Английский

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