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Scalable Solvers Group

Roel Van Beeumen

Roel Van Beeumen
Roel Van Beeumen
Research Scientist
Applied Mathematics and Computational Research Division
Phone: +1 (510) 486-5175
Lawrence Berkeley National Laboratory
1 Cyclotron Road
Mailstop 50A-3111
Berkeley, California 94720 us


  • Research Scientist, Computational Research Division, Berkeley Lab, June 2019 - present.
  • Postdoctoral FellowComputational Research Division, Berkeley Lab, September 2016 - May 2019.
  • Postdoctoral Researcher, Department of Computer Science, KU Leuven, May 2015 - August 2016.
  • PhD ResearcherDepartment of Computer Science, KU Leuven, October 2011 - April 2015. 

Research Interests

  • (Nonlinear) Eigenvalue Problems
  • Numerical Linear Algebra
  • Model Order Reduction
  • Numerical Software
  • Quantum Computing


  • Doctor of Engineering Science (PhD): Computer Science
    2011-2015, KU Leuven, Belgium.
  • Master of Arts in Archaeology
    2010-2011, KU Leuven, Belgium.
  • Master of Engineering: Mathematical Engineering
    2008-2010, KU Leuven, Belgium.
  • Bachelor of Archaeology
    2006-2010, KU Leuven, Belgium.
  • Bachelor of Engineering: Mechanical Engineering
    2005-2008, KU Leuven, Belgium.


  • Y. Shen, D. Camps, S. Darbha, A. Szasz, K. Klymko, D.B. Williams-Young, N.M. Tubman, R. Van Beeumen
    "Estimating eigenenergies from quantum dynamics: A unified noise-resilient measurement-driven approach"
  • E. Kökcü, D. Camps, L. Bassman Oftelie, W.A. de Jong, R. Van Beeumen, A.F. Kemper
    "Algebraic compression of free fermionic quantum circuits: Particle creation, arbitrary lattices and controlled evolution"
  • R. Van Beeumen, D. Camps, N. Mehta
    "QCLAB++: Simulating quantum circuits on GPUs"
  • D. Camps, L. Lin, R. Van Beeumen, C. Yang
    "Explicit quantum circuits for block encodings of certain sparse matrices"

For a complete list see here.


Journal Articles

Jan Balewski, Mercy G Amankwah, Roel Van Beeumen, E Wes Bethel, Talita Perciano, Daan Camps, "Quantum-parallel vectorized data encodings and computations on trapped-ion and transmon QPUs", Journal, February 10, 2024, 14, doi:

E Wes Bethel, Mercy G Amankwah, Jan Balewski, Roel Van Beeumen, Daan Camps, Daniel Huang, Talita Perciano, "Quantum computing and visualization: A disruptive technological change ahead", Journal, November 6, 2023, 43, doi:

M. G. Amankwah, D. Camps, E. W. Bethel, R. Van Beeumen, T. Perciano, "Quantum pixel representations and compression for N-dimensional images", Nature Scientific Reports, May 11, 2022, 12:7712, doi: 10.1038/s41598-022-11024-y

Daan Camps, Roel Van Beeumen, "Approximate quantum circuit synthesis using block encodings", PHYSICAL REVIEW A, November 11, 2020, 102, doi: 10.1103/PhysRevA.102.052411

One of the challenges in quantum computing is the synthesis of unitary operators into quantum circuits with polylogarithmic gate complexity. Exact synthesis of generic unitaries requires an exponential number of gates in general. We propose a novel approximate quantum circuit synthesis technique by relaxing the unitary constraints and interchanging them for ancilla qubits via block encodings. This approach combines smaller block encodings, which are easier to synthesize, into quantum circuits for larger operators. Due to the use of block encodings, our technique is not limited to unitary operators and can be applied for the synthesis of arbitrary operators. We show that operators which can be approximated by a canonical polyadic expression with a polylogarithmic number of terms can be synthesized with polylogarithmic gate complexity with respect to the matrix dimension.

T. Hernandez, R. Van Beeumen, M. Caprio, C. Yang, "A greedy algorithm for computing eigenvalues of a symmetric matrix with localized eigenvectors", Numerical Linear Algebra and Applications, October 9, 2020, 28:e2341, doi:

D. Camps, R. Van Beeumen, C. Yang, "Quantum Fourier Transform Revisited", Numerical Linear Algebra and Applications, September 15, 2020, 28:e2331, doi:

Miroslav Urbanek, Daan Camps, Roel Van Beeumen, Wibe A. de Jong, "Chemistry on quantum computers with virtual quantum subspace expansion", Journal of Chemical Theory and Computation, 2020, 16:5425–5431, doi: 10.1021/acs.jctc.0c00447

B. Peng, R. Van Beeumen, D.B. Williams-Young, K. Kowalski, C. Yang, "Approximate Green’s function coupled cluster method employing effective dimension reduction", Journal of Chemical Theory and Computation, 2019, 15:3185-3196, doi: 10.1021/acs.jctc.9b00172

R. Van Beeumen, O. Marques, E.G. Ng, C. Yang, Z. Bai, L. Ge, O. Kononenko, Z. Li, C.-K. Ng, L. Xiao, "Computing resonant modes of accelerator cavities by solving nonlinear eigenvalue problems via rational approximation", Journal of Computational Physics, 2018, 374:1031-1043, doi: 10.1016/

M. Papadopoulos, R. Van Beeumen, S. François, G. Degrande, G. Lombaert, "Modal characteristics of structures considering dynamic soil-structure interaction effects", Soil Dynamics and Earthquake Engineering, 2018, 105:114-118, doi: 10.1016/j.soildyn.2017.11.012

R. Van Beeumen, D.B. Williams-Young, J.M. Kasper, C. Yang, E.G. Ng, X. Li, "Model order reduction algorithm for estimating the absorption spectrum", Journal of Chemical Theory and Computation, 2017, 13:4950-4961, doi: 10.1021/acs.jctc.7b00402

K. Meerbergen, W. Michiels, R. Van Beeumen, E. Mengi, "Computation of pseudospectral abscissa for large-scale nonlinear eigenvalue problems", IMA Journal of Numerical Analysis, 2017, 37:1831-1863, doi: 10.1093/imanum/drw065

R. Van Beeumen, E. Jarlebring, W. Michiels, "A rank-exploiting infinite Arnoldi algorithm for nonlinear eigenvalue problems", Numerical Linear Algebra with Applications, 2016, 23:607-628, doi: 10.1002/nla.2043

R. Van Beeumen, K. Meerbergen, W. Michiels, "Compact rational Krylov methods for nonlinear eigenvalue problems", SIAM Journal on Matrix Analysis and Applications, 2015, 36:820-838, doi: 10.1137/140976698

R. Van Beeumen, W. Michiels, K. Meerbergen, "Linearization of Lagrange and Hermite interpolating matrix polynomials", IMA Journal of Numerical Analysis, 2015, 35:909-930, doi: 10.1093/imanum/dru019

S. Güttel, R. Van Beeumen, K. Meerbergen, W. Michiels, "NLEIGS: A class of fully rational Krylov methods for nonlinear eigenvalue problems", SIAM Journal on Scientific Computing, 2014, 36:A2842-A286, doi: 10.1137/130935045

W.G. Vandenberghe, M.V. Fischetti, R. Van Beeumen, K. Meerbergen, W. Michiels, C. Effenberger, "Determining bound states in a semiconductor device with contacts using a nonlinear eigenvalue solver", Journal of Computational Electronics, 2014, 13:753-762, doi: 10.1007/s10825-014-0597-5

D. Verhees, R. Van Beeumen, K. Meerbergen, N. Guglielmi, W. Michiels, "Fast algorithms for computing the distance to instability of nonlinear eigenvalue problems, with application to time-delay systems", International Journal of Dynamics and Control, 2014, 2:133-142, doi: 10.1007/s40435-014-0059-8

R. Van Beeumen, K. Meerbergen, W. Michiels, "A rational Krylov method based on Hermite interpolation for nonlinear eigenvalue problems", SIAM Journal on Scientific Computing, 2013, 35:A327-A350, doi: 10.1137/120877556

R. Van Beeumen, K. Van Nimmen, G. Lombaert, K. Meerbergen, "Model reduction for dynamical systems with quadratic output", International Journal for Numerical Methods in Engineering, 2012, 91:229-248, doi: 10.1002/nme.4255

Conference Papers

R. Van Beeumen, G. D. Kahanamoku-Meyer, N. Y. Yao and C. Yang, "A scalable matrix-free iterative eigensolver for studying many-body localization", HPCAsia2020: Proceedings of the International Conference on High Performance Computing in Asia-Pacific Region, ACM, January 7, 2020, 179-187, doi: 10.1145/3368474.3368497


R. Van Beeumen, L. Perisa, D. Kressner, C. Yang, "A Flexible Power Method for Solving Infinite Dimensional Tensor Eigenvalue Problems", January 30, 2021,

Roel Van Beeumen, Khaled Z. Ibrahim, Gregory D. Kahanamoku-Meyer, Norman Y. Yao, Chao Yang, "Enhancing Scalability of a Matrix-Free Eigensolver for Studying Many-Body Localization", December 1, 2020,