Quantifying entanglement of rotor chains using basis truncation: Application to dipolar endofullerene peapods
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Date
2018-02-21
Authors
Halverson, Tom
Iouchtchenko, Dmitri
Roy, Pierre-Nicholas
Journal Title
Journal ISSN
Volume Title
Publisher
American Institute of Physics
Abstract
We propose a variational approach for the calculation of the quantum entanglement entropy of assemblies of rotating dipolar molecules. A basis truncation scheme based on the total angular momentum quantum number is proposed. The method is tested on hydrogen fluoride (HF) molecules confined in C60 fullerene cages themselves trapped in a nanotube to form a carbon peapod. The rotational degrees of freedom of the HF molecules and dipolar interactions between neighboring molecules are considered in our model Hamiltonian. Both screened and unscreened dipoles are simulated and results are obtained for the ground state and one excited state that is expected to be accessible via a far-infrared collective excitation. The effect of basis truncation on energetic and entanglement properties is examined and discussed in terms of size extensivity. It is empirically found that for unscreened dipoles, a total angular momentum cutoff that increases linearly with the number of rotors is required in order to obtain proper system size scaling of the chemical potential and entanglement entropy. Recent experiments [A. Krachmalnicoff et al., Nat. Chem. 8, 953 (2016)] suggest substantial screening of the HF dipole moment, so much smaller basis sets are required to obtain converged results in this realistic case. Static correlation functions are also computed and are shown to decay much quicker in the case of screened dipoles. Our variational results are also used to test the accuracy of perturbative and pairwise ansatz treatments.
Description
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Halverson, T., Iouchtchenko, D., & Roy, P.-N. (2018). Quantifying entanglement of rotor chains using basis truncation: Application to dipolar endofullerene peapods. Journal of Chemical Physics, 148(7), 074112 and may be found at https://doi.org/10.1063/1.5011769
Keywords
Inorganic compounds, Fullerenes, Quantum computing, Zero point energy, Quantum entanglement