Frederik Ravn Klausen

Postdoctoral Researcher
University of Cambridge

Email: frk23@cam.ac.uk

Mathematician working quantitatively with complex systems: quantum, classical and electoral at University of Cambridge.

Before that I was at Princeton and in QMATH and NQCP at the University of Copenhagen.

Jan 2026: Hvis du gerne vil læse om sandsynligheden for overrepræsentation ved danske folketingsvalg klik her.

Below you will find an overview of my research interest as well as a list of publications.

Publications

A list of my publications can also be found on Google Scholar.

• A. J. Bay-Smidt, F. R. Klausen, C. Sünderhauf, R. Izsák, G. C. Solomon, N. S. Blunt.
  Fault-Tolerant Quantum Simulation of Generalized Hubbard Models , PRX Quantum, 6, 030348, 2025.

• U. Thinggaard Hansen, F. R. Klausen, P. Wildemann.
  Non-uniqueness of phase transitions for graphical representations of the Ising model on tree-like graphs , ALEA, Latin American Journal of Probability and Mathematical Statistics, 22, 889-904, 2025.

• U. Hansen, B. Kjær, F. R. Klausen.
  The Uniform Even Subgraph and Its Connection to Phase Transitions of Graphical Representations of the Ising Model , Communications in Mathematical Physics , 2025.

• F. R. Klausen, S. Warzel.
  Decoherence is an echo of Anderson localization in open quantum systems , Annales Henri Poincaré, 2025.

• D. Harley, I. Datta, F. R. Klausen, A. Bluhm, D. S. França, A. Werner, M. Christandl.
  Going Beyond Gadgets: The Importance of Scalability for Analogue Quantum Simulators , Nature Communications, 2024.


• F. R. Klausen, A. Lauritzen.
  A stochastic cellular automaton model of culture formation , Phys. Rev. E, 108, 054307, 2023.


• U. Hansen, F. R. Klausen.
  Strict monotonicity, continuity and bounds on the Kertész line for the random-cluster model on ℤ^d , Journal of Mathematical Physics, 2023.


• F. R. Klausen, A. Raoufi.
  Mass scaling of the near-critical 2D Ising model using random currents , Journal of Statistical Physics, 2022.


• F. R. Klausen.
  On monotonicity and couplings of random currents and the loop-O(1)-model , ALEA. Latin American Journal of Probability and Mathematical Statistics, 2022.


• A. Bluhm, M. Christandl, F. Gesmundo, F. R. Klausen, L. Mančinska, V. Steffan, D. S. França, A. Werner.
  SARS-CoV-2 transmission routes from genetic data: A Danish case study , PloS One, 2020.


• P. Jensen, F. R. Klausen, P. Rasmussen.
  Combinatorial classification of quantum lens spaces , Pacific Journal of Mathematics, 2018.


• S. Holdum, F. R. Klausen, P. Rasmussen.
  Powers in Prime Bases and a Problem on the Central Binomial Coefficient , Integers: Electronic Journal of Combinatorial Number Theory , 2014.


• S. Holdum, F. R. Klausen, P. Rasmussen.
  On a Conjecture on the Representation of Positive Integers as the Sum of Three Terms of the Sequence ⌊n² / a⌋ , The Journal of Integer Sequences, 2014.

Preprints

• U. T. Hansen, J. Jiang, F. R. Klausen
  General coupling for Ising models and beyond , 2025.

• F. R. Klausen, A. Werner.
  Spectra of Lindbladians on the infinite line: From non-Hermitian to full evolution via tridiagonal Laurent matrices , 2022.
• J. Elklit, S. Holudm, F. R. Klausen.
  What is wrong with the proportionality in the Parliamentary Elections Act—and what can be done about it? , (accepted in) Politica, 2025.

Preprints (only here)

• F. R. Klausen.
  The Disproportionate Power of Votes Near Electoral Thresholds, 2025. Download (PDF)


• S. Holdum, F. R. Klausen.
  Impossibility Theorem for Two-Tier Electoral Systems, 2025. Download (PDF)
• F. R. Klausen.
  Sandsynligheden for overrepræsentation ved Folketingsvalg, 2025. Download (PDF)