The Lorentz group, which is the underlying scientific language for modern optics, has most notably been used for understanding Einstein's special relativity. By using a simplified approach of two-by-two matrices and Wigner functions, this book provides a basic and novel approach to classical and quantum optics, making these difficult subjects more transparent to the reader. Written by three experts in the field, Sibel Başkal, Young S Kim and Marilyn E Noz, this book will provide the reader with a comprehensive overview of how fundamental issues in quantum mechanics can be approached using various optical instruments, Wigner functions and quantum entanglement.