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@TECHREPORT{Symeonidou:1018221,
      author       = {Symeonidou, Stefania},
      title        = {{T}he {V}ariational {Q}uantum {E}igensolver in {Q}uantum
                      {C}hemistry with {P}enny{L}ane},
      volume       = {4443},
      number       = {4443},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2023-04617, 4443},
      series       = {Berichte des Forschungszentrums Jülich},
      pages        = {68},
      year         = {2023},
      abstract     = {This thesis explores quantum chemistry using the
                      Variational Quantum Eigensolver (VQE), developed with the
                      help of PennyLane’s quantum chemistry library. Our focus
                      was on exploring molecular structures and energy landscapes.
                      With an adaptive VQE implementation, we generated
                      approximate multi-electron wave functions by optimizing a
                      quantum circuit on a simulator. We started from a
                      Hartree-Fock state and applied the UCCSD (Unitary Coupled
                      Cluster Singles and Doubles) Ansatz to entangle electrons
                      and lower the Hamiltonian’s expectation value. The journey
                      began with H2, where the VQE accurately predicted its
                      equilibrium distance and energy. We then extended our
                      analysis to more complex molecules like LiH, BeH2, and H2O,
                      successfully determining their equilibrium geometries and
                      energies, which match existing literature. However, we
                      discovered anomalies in the energy surfaces of BeH2 and H2O
                      at larger internuclear distances, leading us to question the
                      choice of initial states for these scenarios. In summary,
                      this work demonstrated the VQE’s potential for accurate
                      molecular simulations. While it excels in capturing ground
                      states for various molecules, challenges remain for large
                      internuclear distances. This sheds light on the evolving
                      landscape of quantum technologies applied to understanding
                      molecular systems.},
      cin          = {PGI-2 / IAS-3},
      cid          = {I:(DE-Juel1)PGI-2-20110106 / I:(DE-Juel1)IAS-3-20090406},
      pnm          = {5221 - Advanced Solid-State Qubits and Qubit Systems
                      (POF4-522)},
      pid          = {G:(DE-HGF)POF4-5221},
      typ          = {PUB:(DE-HGF)3 / PUB:(DE-HGF)29},
      doi          = {10.34734/FZJ-2023-04617},
      url          = {https://juser.fz-juelich.de/record/1018221},
}