He is currently Professor of Physics of Information at University College London, and Director of Quantum Computing at Amazon Web Services in Seattle.
Severini worked in quantum information science and complex systems.
Together with Adan Cabello and Andreas Winter, he defined a graph-theoretic framework for studying quantum contextuality, and together with Tomasz Konopka, Fotini Markopoulou, and Lee Smolin, he introduced a random graph model of spacetime called quantum graphity.
In 2015 he was the technical co-founder and one of the first scientific advisors of Cambridge Quantum Computing, with Béla Bollobás, Imre Leader, and Fernando Brandão.
He co-founded Phasecraft[5] in 2018 with Toby Cubitt, Ashley Montanaro, and John Morton.