Floquet Hamiltonian and Entanglement in Spin Systems in Periodic Magnetic Fields
- Authors: Fel’dman E.B.1, Feldman D.E.2, Kuznetsova E.I.1
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Affiliations:
- Institute of Problems of Chemical Physics of RAS
- Department of Physics, Brown University
- Issue: Vol 48, No 6 (2017)
- Pages: 517-531
- Section: Original Paper
- URL: https://journals.rcsi.science/0937-9347/article/view/247702
- DOI: https://doi.org/10.1007/s00723-017-0879-8
- ID: 247702
Cite item
Abstract
We investigate entanglement in a two-spin system with the dipole–dipole interaction in the multi-pulse spin locking nuclear magnetic resonance (NMR) experiment. We discover a conflict between an exact solution and the standard approximation employing a time-independent effective Floquet Hamiltonian. While the exact solution shows nonzero entanglement in the system, the perturbative Floquet approach predicts that entanglement is absent. The failure of the Floquet method is explained by the multivaluedness of the Floquet Hamiltonian. Correct results can only be obtained with a proper choice of the branch of the Hamiltonian. The same issue is present in other applications of the Floquet theorem in the perturbation theory beyond NMR.
About the authors
E. B. Fel’dman
Institute of Problems of Chemical Physics of RAS
Email: kuznets@icp.ac.ru
Russian Federation, Chernogolovka, Moscow Region, 142432
D. E. Feldman
Department of Physics, Brown University
Email: kuznets@icp.ac.ru
United States, Providence, RI, 02912
E. I. Kuznetsova
Institute of Problems of Chemical Physics of RAS
Author for correspondence.
Email: kuznets@icp.ac.ru
Russian Federation, Chernogolovka, Moscow Region, 142432