Subspace methods for the simulation of molecular response properties on a quantum computer

Peter Reinholdt, Erik Rosendahl Kjellgren*, Juliane Holst Fuglsbjerg, Karl Michael Ziems, Sonia Coriani, Stephan P. A. Sauer, Jacob Kongsted

*Corresponding author for this work

Research output: Working paperPreprintResearch

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Abstract

We explore Davidson methods for obtaining excitation energies and other linear response properties within quantum self-consistent linear response (q-sc-LR) theory. Davidson-type methods allow for obtaining only a few selected excitation energies without explicitly constructing the electronic Hessian since they only require the ability to perform Hessian-vector multiplications. We apply the Davidson method to calculate the excitation energies of hydrogen chains (up to H10) and analyze aspects of statistical noise for computing excitation energies on quantum simulators. Additionally, we apply Davidson methods for computing linear response properties such as static polarizabilities for H2, LiH, H2O, OH−, and NH3, and show that unitary coupled cluster outperforms classical projected coupled cluster for molecular systems with strong correlation. Finally, we formulate the Davidson method for damped (complex) linear response, with application to the nitrogen K-edge X-ray absorption of ammonia, and the C6 coefficients of H2, LiH, H2O, OH−, and NH3.
Original languageEnglish
Publisherarxiv.org
Volume2402.12186
Number of pages35
DOIs
Publication statusPublished - 19 Feb 2024

Keywords

  • Faculty of Science
  • Quantum Computing
  • linear response theory
  • excitation energies
  • polarizability

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