| 1. |
- Lolur, Phalgun, 1989, et al.
(författare)
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Benchmarking the variational quantum eigensolver through simulation of the ground state energy of prebiotic molecules on high-performance computers
- 2021
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Ingår i: AIP Conference Proceedings. - : AIP Publishing. - 1551-7616 .- 0094-243X. ; 2362
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Konferensbidrag (refereegranskat)abstract
- We use the Variational Quantum Eigensolver (VQE) as implemented in the Qiskit software package to compute the ground state energy of small molecules derived from water, H2O, and hydrogen cyanide, HCN. The work aims to benchmark algorithms for calculating the electronic structure and energy surfaces of molecules of relevance to prebiotic chemistry, beginning with water and hydrogen cyanide, and to run them on the available simulated and physical quantum hardware. The numerical calculations of the algorithms for small quantum processors allow us to design more efficient protocols to be run in real hardware, as well as to analyze their performance. Future implementations on accessible quantum processing prototypes will benchmark quantum computers and provide tests of quantum advantage with heuristic quantum algorithms.
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| 2. |
- Lolur, Phalgun, 1989, et al.
(författare)
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Reference-State Error Mitigation: A Strategy for High Accuracy Quantum Computation of Chemistry
- 2023
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9626 .- 1549-9618. ; 19:3, s. 783-789
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Tidskriftsartikel (refereegranskat)abstract
- Decoherence and gate errors severely limit the capabilities of state-of-the-art quantum computers. This work introduces a strategy for reference-state error mitigation (REM) of quantum chemistry that can be straightforwardly implemented on current and near-term devices. REM can be applied alongside existing mitigation procedures, while requiring minimal postprocessing and only one or no additional measurements. The approach is agnostic to the underlying quantum mechanical ansatz and is designed for the variational quantum eigensolver. Up to two orders-of-magnitude improvement in the computational accuracy of ground state energies of small molecules (H2, HeH+, and LiH) is demonstrated on superconducting quantum hardware. Simulations of noisy circuits with a depth exceeding 1000 two-qubit gates are used to demonstrate the scalability of the method.
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| 3. |
- Racioppi, Stefano, 1990, et al.
(författare)
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A Density Functional Theory for the Average Electron Energy
- 2023
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Ingår i: Journal of Chemical Theory and Computation. - : American Chemical Society (ACS). - 1549-9626 .- 1549-9618. ; 19:3, s. 799-807
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Tidskriftsartikel (refereegranskat)abstract
- A formally exact density functional theory (DFT) determination of the average electron energy is presented. Our theory, which is based on a different accounting of energy functional terms, partially solves one well-known downside of conventional Kohn-Sham (KS) DFT: that electronic energies have but tenuous connections to physical quantities. Calculated average electron energies are close to experimental ionization potentials (IPs) in one-electron systems, demonstrating a surprisingly small effect of self-interaction and other exchange-correlation errors in established DFT methods. Remarkable agreement with ab initio quantum mechanical calculations of multielectron systems is demonstrated using several flavors of DFT, and we argue for the use of the average electron energy as a design criterion for density functional approximations.
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| 4. |
- Skogh, Mårten, 1994, et al.
(författare)
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Accelerating variational quantum eigensolver convergence using parameter transfer
- 2023
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Ingår i: Electronic Structure. - 2516-1075. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- One impediment to the useful application of variational quantum algorithms in quantum chemistry is slow convergence with large numbers of classical optimization parameters. In this work, we evaluate a quantum computational warm-start approach for potential energy surface calculations. Our approach, which is inspired by conventional computational methods, is evaluated using simulations of the variational quantum eigensolver. Significant speedup is demonstrated relative to calculations that rely on a Hartree-Fock initial state, both for ideal and sampled simulations. The general approach of transferring parameters between similar problems is promising for accelerating current and near-term quantum chemistry calculations on quantum hardware, and is likely applicable beyond the tested algorithm and use case.
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| 5. |
- Skogh, Mårten, 1994, et al.
(författare)
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The electron density: a fidelity witness for quantum computation
- 2023
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Ingår i: Chemical Science. - 2041-6539 .- 2041-6520. ; 15:6, s. 2257-2265
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Tidskriftsartikel (refereegranskat)abstract
- There is currently no combination of quantum hardware and algorithms that can provide an advantage over conventional calculations of molecules or materials. However, if or when such a point is reached, new strategies will be needed to verify predictions made using quantum devices. We propose that the electron density, obtained through experimental or computational means, can serve as a robust benchmark for validating the accuracy of quantum computation of chemistry. An initial exploration into topological features of electron densities, facilitated by quantum computation, is presented here as a proof of concept. Additionally, we examine the effects of constraining and symmetrizing measured one-particle reduced density matrices on noise-driven errors in the electron density distribution. We emphasize the potential benefits and future need for high-quality electron densities derived from diffraction experiments for validating classically intractable quantum computations of materials.
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