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

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(9), С. 3613 - 3625

Опубликована: Май 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.

Язык: Английский

---

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

Chemical Science, Год журнала: 2025, Номер 16(10), С. 4456 - 4468

Опубликована: Янв. 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.

Язык: Английский

---

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

---

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

---

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

The Journal of Chemical Physics, Год журнала: 2025, Номер 162(15)

Опубликована: Апрель 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.

Язык: Английский

---

Quantum Computation of Conical Intersections on a Programmable Superconducting Quantum Processor

The Journal of Physical Chemistry Letters, Год журнала: 2024, Номер 15(28), С. 7244 - 7253

Опубликована: Июль 8, 2024

Conical intersections (CIs) are pivotal in many photochemical processes. Traditional quantum chemistry methods, such as the state-average multiconfigurational face computational hurdles solving electronic Schrödinger equation within active space on classical computers. While computing offers a potential solution, its feasibility studying CIs, particularly real hardware, remains largely unexplored. Here, we present first successful realization of hybrid quantum-classical complete self-consistent field method based variational eigensolver (VQE-SA-CASSCF) superconducting processor. This approach is applied to investigate CIs two prototypical systems─ethylene (C

Язык: Английский

---

Reduced Density Matrix Formulation of Quantum Linear Response

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер unknown

Опубликована: Авг. 6, 2024

The prediction of spectral properties via linear response (LR) theory is an important tool in quantum chemistry for understanding photoinduced processes molecular systems. With the advances computing, we recently adapted this method near-term hardware using a truncated active space approximation with orbital rotation, named (qLR). In effort to reduce classic cost hybrid approach, here derive and implement reduced density matrix (RDM) driven approach qLR. This allows calculation moderately sized molecules much larger basis sets than so far possible. We report qLR results benzene

Язык: Английский

---

Divergences in classical and quantum linear response and equation of motion formulations

The Journal of Chemical Physics, Год журнала: 2024, Номер 161(12)

Опубликована: Сен. 25, 2024

Calculating molecular properties using quantum devices can be performed through the linear response (qLR) or, equivalently, equation of motion (qEOM) formulations. Different parameterizations qLR and qEOM are available, namely naïve, projected, self-consistent, state-transfer. In naïve projected parameterizations, metric is not identity, we show that it depends on redundant orbital rotations. This dependency may lead to divergences in excitation energies for certain choices rotation parameters an idealized noiseless setting. Furthermore, this leads a significant variance when calculations include statistical noise from finite sampling.

Язык: Английский

---

Determining the N-Representability of a Reduced Density Matrix via Unitary Evolution and Stochastic Sampling

Journal of Chemical Theory and Computation, Год журнала: 2024, Номер 20(22), С. 9968 - 9976

Опубликована: Ноя. 14, 2024

The N-representability problem consists in determining whether, for a given p-body matrix, there exists at least one N-body density matrix from which the can be obtained by contraction, that is, if is reduced (p-RDM). knowledge of all necessary and sufficient conditions to N-representable allows constrained minimization many-body Hamiltonian expectation value with respect and, thus, determination its exact ground state. However, number constraints complete grows exponentially system size, hence, procedure quickly becomes intractable practical applications. This work introduces hybrid quantum-stochastic algorithm effectively replace conditions. applying an initial sequence unitary evolution operators constructed stochastic process successively approaches state on subsystem, represented p-RDM, target potentially p-RDM. generators follow well-known adaptive derivative-assembled pseudo-Trotter method (ADAPT), while component implemented using simulated annealing process. resulting independent any underlying Hamiltonian, it used decide whether N-representable, establishing criterion determine quality correcting it. We apply proposed ADAPT alleged matrices quantum chemistry electronic Bardeen–Cooper–Schrieffer model constant pairing, Heisenberg XXZ spin model. In cases, behaves as expected 1-RDMs 2-RDMs, evolving toward different targets.

Язык: Английский

---