Quantum channel capacities are known to exhibit counterintuitive properties (superadditivity and superactivation), which make them hard to calculate. In this episode we talk to Debbie Leung (Institute for Quantum Computing, University of Waterloo) about one of her favourite open problems, the capacity of the qubit depolarizing channel, as well as her 2017 paper with Felix Leditzky and Graeme Smith that makes some progress on this problem. Hosts: Vincent Russo (vprusso.github.io), William Slofstra (elliptic.space), Henry Yuen (henryyuen.net) Debbie's paper: https://doi.org/10.1103/PhysRevLett.120.160503 Beyond IID in Information Theory: https://sites.google.com/view/beyondiid8/ Link to Debbie's course on quantum channel capacities: https://www.math.uwaterloo.ca/~wcleung/co781-f2020.html Music by Vincent Russo. Theme is WLIIAW.