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@ARTICLE{Guo:619662,
      author       = {Guo, Yibin and Angelides, Takis and Jansen, Karl and Kühn,
                      Stefan},
      title        = {{C}oncurrent {VQE} for {S}imulating {E}xcited {S}tates of
                      the {S}chwinger {M}odel},
      reportid     = {PUBDB-2024-07801, arXiv:2407.15629},
      year         = {2024},
      note         = {21 pages, 17 figures, 3 tables, comments are welcome!},
      abstract     = {This work explores the application of the concurrent
                      variational quantum eigensolver (cVQE) for computing excited
                      states of the Schwinger model. By designing suitable ansatz
                      circuits utilizing universal SO(4) or SO(8) qubit gates, we
                      demonstrate how to efficiently obtain the lowest two, four,
                      and eight eigenstates with one, two, and three ancillary
                      qubits for both vanishing and non-vanishing background
                      electric field cases. Simulating the resulting quantum
                      circuits classically with tensor network techniques, we
                      demonstrate the capability of our approach to compute the
                      two lowest eigenstates of systems with up to
                      $\mathcal{O}(100)$ qubits. Given that our method allows for
                      measuring the low-lying spectrum precisely, we also present
                      a novel technique for estimating the additive mass
                      renormalization of the lattice based on the energy gap. As a
                      proof-of-principle calculation, we prepare the ground and
                      first-excited states with one ancillary and four physical
                      qubits on quantum hardware, demonstrating the practicality
                      of using the cVQE to simulate excited states.},
      cin          = {CQTA},
      cid          = {I:(DE-H253)CQTA-20221102},
      pnm          = {611 - Fundamental Particles and Forces (POF4-611) / QUEST -
                      QUantum computing for Excellence in Science and Technology
                      (101087126)},
      pid          = {G:(DE-HGF)POF4-611 / G:(EU-Grant)101087126},
      experiment   = {EXP:(DE-MLZ)NOSPEC-20140101},
      typ          = {PUB:(DE-HGF)25},
      eprint       = {2407.15629},
      howpublished = {arXiv:2407.15629},
      archivePrefix = {arXiv},
      SLACcitation = {$\%\%CITATION$ = $arXiv:2407.15629;\%\%$},
      url          = {https://bib-pubdb1.desy.de/record/619662},
}