He held the Chair of Combinatorial Analysis in the Institute of Mathematics at the École Polytechnique Fédérale de Lausanne until February 2023.
Following his graduation in 2008, he spent four years as a Gibbs Assistant Professor in Applied Mathematics at Yale University.
In 2012, Marcus cofounded Crisply, an analytics company in Boston, Massachusetts, where he served as chief scientist until 2015.
[10] A team consisting of Marcus, Daniel Spielman, and Nikhil Srivastava was awarded the 2014 Pólya Prize for their resolution of the Kadison–Singer problem.
[12] The team of Marcus, Spielman, and Srivastava was also awarded the 2021 Michael and Sheila Held Prize for their work in resolving the Kadison–Singer problem and their solution to long-standing conjectures in the study of Ramanujan graphs.