Rui Barbosa

Staff Researcher
Quantum and Linear-Optical Computation

Rui is a Staff Researcher at the Quantum and Linear-Optical Computation group at INL.
His interests lie at the intersection of Computer Science, Physics, and Mathematics. Broadly speaking, his research addresses interrelated questions on quantum foundations, quantum computer science, and the mathematics of quantum theory, with an emphasis on logical, structural, and compositional aspects.

It aims to achieve a general, structural understanding of the characteristically non-classical features of quantum systems, which sheds light on their potential – and limitations – as informatics or computational resources, thus delineating the scope of quantum advantage. An eventual hope is that such a foundational perspective can guide the development of systematic, modular methods for utilising quantum resources. In pursuing these goals, his research employs viewpoints and tools from a range of areas in mathematics and theoretical computer science, including category theory (sheaves, monoidal categories, closed categories, monads and comonads, …), logic and related algebraic structures, probability, algebraic topology, and operator algebras.

In particular, most of his research to date has focused on the study of non-localilty and contextuality, phenomena that set quantum theory apart from classical physical theories and which have been linked to quantum informatic advantage. In contrast with the classical case, not all observables of a quantum system can be measured and be assigned values simultaneously. Contexts of jointly measurable observables provide multiple partial, classical perspectives on a quantum system. But while any two of these contexts fit nicely together, they cannot all be pasted consistently into a global perspective. This gap between local consistency and global inconsistency is what constitutes contextuality, a concept that finds an elegant expression in the language of sheaf theory.

Rui holds a BSc in Computer Science from Universidade do Minho (2009), an MSc in Mathematics and Foundations of Computer Science from the University of Oxford (2010), and a DPhil in Computer Science also from Oxford (2015), with a thesis on Contextuality in quantum mechanics and beyond. Before moving to INL, I held post-doctoral positions at Oxford (2015–2019) and the University of Edinburgh (2019–2020).

More details can be found on his personal webpage.

Selected Publications

  • S. Abramsky and R. S. Barbosa
    The logic of contextuality
    29th EACSL Annual Conference on Computer Science Logic (CSL 2021), C. Baier and J. Goubault-Larrecq (eds)
    Leibniz International Proceedings in Informatics (LIPIcs), 183: 5:1–5:18 (2021)
    arXiv:2011.03064 [quant-ph]
  • S. Abramsky, R. S. Barbosa, M. Karvonen, and S. Mansfield
    A comonadic view of simulation and quantum resources
    34th Annual ACM/IEEE Symposium on Logic in Computer Science (LiCS 2019): 1–12 (2019)
    arXiv:1904.10035 [quant-ph]
  • S. Abramsky, R. S. Barbosa, and S. Mansfield
    Contextual fraction as a measure of contextuality
    Physical Review Letters, 119: 050504 (2017)
    arXiv:1705.07918 [quant-ph]
  • S. Abramsky, R. S. Barbosa, K. Kishida, R. Lal, and S. Mansfield
    Contextuality, cohomology and paradox
    24th EACSL Annual Conference on Computer Science Logic (CSL 2015), S. Kreutzer (ed.)
    Leibniz International Proceedings in Informatics (LIPIcs), 41: 211–228 (2015)
    arXiv:1502.03097 [quant-ph]
  • N. de Silva and R. S. Barbosa
    Contextuality and noncommutative geometry in quantum mechanics
    Communications in Mathematical Physics, 365(2): 375–429 (2019)
    arXiv:1806.02840 [math.OA]