Werner Dobrautz

2024

1. Quantum

   Optimizing Variational Quantum Algorithms with qBang: Efficiently Interweaving Metric and Momentum to Navigate Flat Energy Landscapes

   David Fitzek, Robert S. Jonsson, Werner Dobrautz, and Christian Schäfer

   Quantum, Apr 2024

   arXiv Bib HTML

   @article{Fitzek2024,
     title = {Optimizing Variational Quantum Algorithms with qBang: Efficiently Interweaving Metric and Momentum to Navigate Flat Energy Landscapes},
     volume = {8},
     issn = {2521-327X},
     url = {http://dx.doi.org/10.22331/q-2024-04-09-1313},
     doi = {10.22331/q-2024-04-09-1313},
     journal = {Quantum},
     publisher = {Verein zur Forderung des Open Access Publizierens in den Quantenwissenschaften},
     author = {Fitzek, David and Jonsson, Robert S. and Dobrautz, Werner and Sch\"{a}fer, Christian},
     year = {2024},
     month = apr,
     pages = {1313},
     project_devel = {true},
     project_quantum = {true},
     dimensions = {true},
   }

2. JCTC

   Toward Real Chemical Accuracy on Current Quantum Hardware Through the Transcorrelated Method

   Werner Dobrautz, Igor O. Sokolov, Ke Liao, Pablo López Ríos, Martin Rahm, and 2 more authors

   Journal of Chemical Theory and Computation, May 2024

   arXiv Bib HTML

   @article{Dobrautz2024,
     title = {Toward Real Chemical Accuracy on Current Quantum Hardware Through the Transcorrelated Method},
     volume = {20},
     issn = {1549-9626},
     url = {http://dx.doi.org/10.1021/acs.jctc.4c00070},
     doi = {10.1021/acs.jctc.4c00070},
     number = {10},
     journal = {Journal of Chemical Theory and Computation},
     publisher = {American Chemical Society (ACS)},
     author = {Dobrautz, Werner and Sokolov, Igor O. and Liao, Ke and Ríos, Pablo López and Rahm, Martin and Alavi, Ali and Tavernelli, Ivano},
     year = {2024},
     month = may,
     pages = {4146–4160},
     project_tc = {true},
     project_quantum = {true},
     dimensions = {true},
   }

3. Faraday Diss.

   Towards efficient quantum computing for quantum chemistry: reducing circuit complexity with transcorrelated and adaptive ansatz techniques

   Erika Magnusson, Aaron Fitzpatrick, Stefan Knecht, Martin Rahm, and Werner Dobrautz

   Faraday Discussions, May 2024

   arXiv Bib HTML

   @article{Magnusson2024,
     title = {Towards efficient quantum computing for quantum chemistry: reducing circuit complexity with transcorrelated and adaptive ansatz techniques},
     volume = {254},
     issn = {1364-5498},
     url = {http://dx.doi.org/10.1039/D4FD00039K},
     doi = {10.1039/d4fd00039k},
     journal = {Faraday Discussions},
     publisher = {Royal Society of Chemistry (RSC)},
     author = {Magnusson, Erika and Fitzpatrick, Aaron and Knecht, Stefan and Rahm, Martin and Dobrautz, Werner},
     year = {2024},
     pages = {402–428},
     project_tc = {true},
     project_quantum = {true},
     dimensions = {true},
   }

2023

1. JCTC

   Reference-State Error Mitigation: A Strategy for High Accuracy Quantum Computation of Chemistry

   Phalgun Lolur, Mårten Skogh, Werner Dobrautz, Christopher Warren, Janka Biznárová, and 5 more authors

   Journal of Chemical Theory and Computation, Jan 2023

   Abs arXiv Bib HTML

   Decoherence and gate errors severely limit the capabilities of state-of-the-art quantum computers. This work introduces a strategy for reference-state error mitigation (REM) of quantum chemistry that can be straightforwardly implemented on current and near-term devices. REM can be applied alongside existing mitigation procedures, while requiring minimal postprocessing and only one or no additional measurements. The approach is agnostic to the underlying quantum mechanical ansatz and is designed for the variational quantum eigensolver. Up to two orders-of-magnitude improvement in the computational accuracy of ground state energies of small molecules (H2, HeH+, and LiH) is demonstrated on superconducting quantum hardware. Simulations of noisy circuits with a depth exceeding 1000 two-qubit gates are used to demonstrate the scalability of the method.

   @article{Lolur2023,
     doi = {10.1021/acs.jctc.2c00807},
     url = {https://doi.org/10.1021/acs.jctc.2c00807},
     year = {2023},
     month = jan,
     publisher = {American Chemical Society ({ACS})},
     volume = {19},
     number = {3},
     pages = {783--789},
     author = {Lolur, Phalgun and Skogh, M{\aa}rten and Dobrautz, Werner and Warren, Christopher and Bizn{\'{a}}rov{\'{a}}, Janka and Osman, Amr and Tancredi, Giovanna and Wendin, G\"{o}ran and Bylander, Jonas and Rahm, Martin},
     title = {Reference-State Error Mitigation: A Strategy for High Accuracy Quantum Computation of Chemistry},
     journal = {Journal of Chemical Theory and Computation},
     dimensions = {true},
     project_quantum = {true},
     project_mitigation = {true}
   }

2. PRResearch

   Orders of magnitude increased accuracy for quantum many-body problems on quantum computers via an exact transcorrelated method

   Igor O. Sokolov, Werner Dobrautz, Hongjun Luo, Ali Alavi, and Ivano Tavernelli

   Phys. Rev. Res., Jun 2023

   Abs arXiv Bib HTML

   Transcorrelated methods provide an efficient way of partially transferring the description of electronic correlations from the ground-state wave function directly into the underlying Hamiltonian. In particular, Dobrautz et al. [Phys. Rev. B 99, 075119 (2019)] have demonstrated that the use of momentum-space representation, combined with a nonunitary similarity transformation, results in a Hubbard Hamiltonian that possesses a significantly more “compact” ground-state wave function, dominated by a single Slater determinant. This compactness/single-reference character greatly facilitates electronic structure calculations. As a consequence, however, the Hamiltonian becomes non-Hermitian, posing problems for quantum algorithms based on the variational principle. We overcome these limitations with the Ansatz-based quantum imaginary-time evolution algorithm and apply the transcorrelated method in the context of digital quantum computing. We demonstrate that this approach enables up to four orders of magnitude more accurate and compact solutions in various instances of the Hubbard model at intermediate interaction strength (U/t=4), enabling the use of shallower quantum circuits for wave-function Ansätzes. In addition, we propose a more efficient implementation of the quantum imaginary-time evolution algorithm in quantum circuits that is tailored to non-Hermitian problems. To validate our approach, we perform hardware experiments on the ibmq_lima quantum computer. Our work paves the way for the use of exact transcorrelated methods for the simulations of ab initio systems on quantum computers.

   @article{PhysRevResearch.5.023174,
     title = {Orders of magnitude increased accuracy for quantum many-body problems on quantum computers via an exact transcorrelated method},
     author = {Sokolov, Igor O. and Dobrautz, Werner and Luo, Hongjun and Alavi, Ali and Tavernelli, Ivano},
     journal = {Phys. Rev. Res.},
     volume = {5},
     issue = {2},
     pages = {023174},
     numpages = {19},
     year = {2023},
     month = jun,
     publisher = {American Physical Society},
     doi = {10.1103/PhysRevResearch.5.023174},
     url = {https://link.aps.org/doi/10.1103/PhysRevResearch.5.023174},
     dimensions = {true},
     project_quantum = {true},
     project_tc = {true},
     project_hubbard = {true}
   }