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@ARTICLE{Mller:1040323,
      author       = {Müller, Thorge and Stollenwerk, Tobias and Headley, David
                      and Epping, Michael and Wilhelm, Frank K},
      title        = {{C}oherent and non-unitary errors in {ZZ}-generated gates},
      journal      = {Quantum science and technology},
      volume       = {10},
      number       = {1},
      issn         = {2058-9565},
      address      = {Philadelphia, PA},
      publisher    = {IOP Publishing},
      reportid     = {FZJ-2025-01837},
      pages        = {015058 -},
      year         = {2025},
      abstract     = {Variational algorithms such as the quantum approximate
                      optimization algorithm have attracted attention due to their
                      potential for solving problems using near-term quantum
                      computers. The ZZ interaction typically generates the
                      primitive two-qubit gate in such algorithms applied for a
                      time, typically a variational parameter, γ. Different
                      compilation techniques exist with respect to the
                      implementation of two-qubit gates. Due to the importance of
                      the ZZ-gate, we present an error analysis comparing the
                      continuous-angle controlled phase gate (CP) against the
                      fixed angle controlled Z-gate (CZ). We analyze both
                      techniques under the influence of coherent over-rotation and
                      depolarizing noise. We show that CP and CZ compilation
                      techniques achieve comparable ZZ-gate fidelities if the
                      incoherent error is below $0.03\%$ and the coherent error is
                      below $0.8\%.$ Thus, we argue that for small coherent and
                      incoherent error a non-parameterized two-qubit gate such as
                      CZ in combination with virtual Z decomposition for
                      single-qubit gates could lead to a significant reduction in
                      the calibration required and, therefore, a less error-prone
                      quantum device. We show that above a coherent error of
                      0.04π $(2\%),$ the CZ gate fidelity depends significantly
                      on γ.},
      cin          = {PGI-12},
      ddc          = {530},
      cid          = {I:(DE-Juel1)PGI-12-20200716},
      pnm          = {BMBF 13N16149 - QSolid (BMBF-13N16149) / 5221 - Advanced
                      Solid-State Qubits and Qubit Systems (POF4-522)},
      pid          = {G:(DE-Juel1)BMBF-13N16149 / G:(DE-HGF)POF4-5221},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:001388382800001},
      doi          = {10.1088/2058-9565/ad9be2},
      url          = {https://juser.fz-juelich.de/record/1040323},
}