---
title: Introduction
description: A free IBM course on quantum information and computation
source: https://quantum.cloud.ibm.com/learning/en/courses/basics-of-quantum-information/quantum-circuits/introduction
---

# Introduction

In the following video, John Watrous steps you through the content in this lesson on quantum circuits. Alternatively, you can open the [YouTube video](https://youtu.be/30U2DTfIrOU?list=PLOFEBzvs-VvqKKMXX4vbi4EB1uaErFMSO) for this lesson in a separate window. [Download the slides](https://ibm.box.com/public/static/zsd4694uko51kzcohdvbp6ncgl9u9ys3.pdf) for this lesson.

This lesson introduces the *quantum circuit* model of computation, which provides a standard way to describe quantum computations.

The lesson also introduces a few important mathematical concepts, including *inner products* between vectors, the notions of *orthogonality* and *orthonormality*, and *projections* and *projective measurements*, which generalize standard basis measurements.
Through these concepts, we'll derive fundamental limitations on quantum information, including the *no-cloning theorem* and the impossibility to perfectly discriminate non-orthogonal quantum states.