Kahn grew up in New York City and attended Hunter College High School.

[1] Kahn was part of the Johns Hopkins University Study of Mathematically Precocious Youth longitudinal cohort.

After that, he worked for the investment firm Highbridge Capital Management as an analyst in financial mathematics.

[6] In 2012, Kahn and Vladimir Markovic received the Clay Research Award for their research on hyperbolic geometry, specifically, for their result on immersions into a closed hyperbolic 3-manifold (proof of the surface subgroup conjecture)[7] and for their proof of the Ehrenpreis conjecture.

[8] In 2014 he was an invited speaker at the International Congress of Mathematicians in Seoul and gave a talk called "The Surface Subgroup and the Ehrenpreis Conjectures".