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

• URL: http://arxiv.org/abs/2406.17141v1
• Date: Mon, 24 Jun 2024 21:22:31 GMT
• Title: Divergences in classical and quantum linear response and equation of motion formulations
• Authors: Erik Rosendahl Kjellgren, Peter Reinholdt, Karl Michael Ziems, Stephan P. A. Sauer, Sonia Coriani, Jacob Kongsted,
• Abstract summary: Calculating molecular properties using quantum devices can be done through the quantum linear response (qLR) or, equivalently, the quantum equation of motion (qEOM) We show that the metric is not the identity, and we show that it depends on the redundant orbital rotations.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Calculating molecular properties using quantum devices can be done through the quantum linear response (qLR) or, equivalently, the quantum equation of motion (qEOM) formulations. Different parameterizations of qLR and qEOM are available, namely naive, projected, self-consistent, and state-transfer. In the naive and projected parameterizations, the metric is not the identity, and we show that it depends on the redundant orbital rotations. This dependency may lead to divergences in the excitation energies for certain choices of the redundant orbital rotation parameters in an idealized noise-less setting. Further, this leads to significant variance when calculations include statistical noise from finite quantum sampling.

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