From the video description: Building reliable large-scale quantum computers is a monumental challenge, due in large part to the fact that quantum information is extremely fragile. Fortunately, we have a key tool to help in this endeavor: quantum error correction. This lesson takes a first look at quantum error correction, including the first quantum error correcting code discovered — the 9-qubit Shor code — and the foundational concept in quantum error correction known as the discretization of errors.