Quantum Computing

Crime is common. Logic is rare. Therefore it is upon the logic rather than upon the crime that you should dwell.

Sir Arthur Conan Doyle, “The Adventure of the Copper Beeches”

Chapter 3 Elementary, My Dear Watson—Quantum Logic

In the previous chapter, we covered how to work with the Measure gate and tip qubits to binary states. We continue building up our toolkit with quantum gates that coax qubits to collapse in controlled ways, for it’s only through precision that qubits can take on our application’s tasks.

In this chapter, you’ll learn about gates that perform logic operations, the bread and butter of computer programs, but on qubits instead of standard binary bits. These gates are like the fuel injectors in your car—by themselves ...