Part 2 Learning information about a quantum system

The second part of the book focuses on quantum measurements and the ways to use them to read out information from a quantum system, whether it is information about a quantum state or a quantum operation.

Chapter 4 focuses on using measurements to get the necessary information about quantum states in a variety of settings. Chapter 5 builds on top of the previous chapter, offering several exercises on getting information about unitary transformations. A big part of chapter 5 is dedicated to the phase estimation problem—finding an eigenvalue associated with the given eigenvector of the given unitary. A lot of quantum computing algorithms include phase estimation as a subtask, and the variety of the approaches they take to solving this problem is a great example of the different types of quantum algorithms.