Research

My research interest is in quantum computation, in particular computational models. One object of study in this field is the one-way quantum computer, a scheme of quantum computation consisting of local measurements on an entangled universal resource state. The questions I ask are ``What are the elementary building blocks of the one-way quantum computer? What is their composition principle?'' I hope that the answer to these questions will give clues for how to construct novel quantum algorithms. Another model of quantum computation that I study are quantum cellular automata (QCA). I am, for example, interested in the question of whether and what type of quantum algorithms can be encoded the shape of the boundary of a finitely extended quantum cellular automaton.

I have invented the one-way quantum computer (QCc) together with Hans Briegel (UK patent GB 2382892, US patent 7,277,872). The QCc is a scheme of universal quantum computation by local measurements on a multi-particle entangled quantum state, the so-called cluster state. Quantum information is written into the cluster state, processed and read out by one-qubit measurements only. As the computation proceeds, the entanglement in the resource cluster state is progressively destroyed. Measurements replace unitary evolution as the elementary process driving a quantum computation.

I also work in the field of fault-tolerant quantum computation. Error-correction is what a large-scale quantum computer spends most of its computation time with, and it is important to devise error-correction methods which allow for a high error threshold at a moderate operational overhead. My research interest is in fault-tolerance for quantum systems with a geometrical constraint, e.g. low-dimensional lattice systems, and in topological methods.

Selected publications

• R. Raussendorf and J. Harrington, Fault-tolerant quantum computation with high threshold in two dimensions, arXiv:quant-ph/0610082, Phys. Rev. Lett. 98, 150504 (2007).

• R. Raussendorf, J. Harrington, K. Goyal A fault-tolerant one-way quantum computer, arXiv:quant-ph/0510135, Ann. Phys. (N.Y.) 321, 2242 (2006).

• R. Raussendorf, S. Bravyi, J. Harrington, Long-range quantum entanglement in noisy cluster states, arXiv:quant-ph/0407255 , Phys. Rev. A 71, 062313 (2005).

• R. Raussendorf and H.-J. Briegel, Computational model underlying the one-way quantum computer, arXiv:quant-ph/0108067, Quant. Inf. Comp. 6, 443 (2002).

• R. Raussendorf and H.-J. Briegel, A one-way quantum computer, (preprint version is entitled ``Quantum computing via measurements only'', arXiv:quant-ph/0010033), Phys. Rev. Lett. 86, 5188 (2001).

• H.-J. Briegel and R. Raussendorf, Persistent Entanglement in Arrays of Interacting Particles , arXiv:quant-ph/0004051, Phys. Rev. Lett. 86, 910 (2001).

A complete list of my publications can be found here.

Brief academic bio

I received my Diploma/Master degree in Physics from the Ruprecht Karls University in Heidelberg, Germany in 1997. My thesis Diploma thesis is on ``A Linear Sigma-Model for Vector and Axial Vector Mesons'' (low-energy quantum chromodynamics). In 1998/99 I did community service at the German Cancer Research Center Heidelberg. In 2003 I obtained my PhD from the Ludwig Maximilians University in Munich, Germany (summa cum laude). My PhD thesis is on measurement-based quantum computation. From 2003 to 2006 I was postdoc at Caltech and I am presently postdoc at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. I will join the Physics and Astronomy department at the University of British Columbia as Assistant Professor in January 2008.

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