This is an announcement for the paper "Interlacing families II: Mixed characteristic polynomials and a question of Kadison and Singer" by Adam Marcus, Daniel A Spielman, and Nikhil Srivastava. Abstract: We use the method of interlacing families of polynomials to prove Weaver's conjecture KS_2, which is known to imply a positive answer to a famous question of Kadison and Singer via Anderson's Paving Conjecture. Our proof goes through an analysis of the largest roots of a family of polynomials that we call the "mixed characteristic polynomials" of a collection of matrices. Archive classification: math.CO math.FA math.OA Submitted from: spielman@cs.yale.edu The paper may be downloaded from the archive by web browser from URL http://front.math.ucdavis.edu/1306.3969 or http://arXiv.org/abs/1306.3969