7.6 Professor Hadamard, meet Professor Pauli

Other than mapping the state of a qubit to a Bloch sphere and looking at it differently, what can you do with a qubit? This section looks at the operations, also called gates, which you can apply to a single qubit. Later, we expand our exploration to gates with multiple qubits as inputs and outputs. In Chapter 9, “Wiring Up the Circuits,” we build circuits with these gates to implement algorithms. gate$quantum gate$reversible

Here, for example, is a circuit with one qubit initialized to |0⟩ that performs one operation, X, and then measures the qubit. The result of the measurement is |m₀⟩.

Quantum gates are always reversible, but some other operations are not. Quantum gates correspond to unitary transformations. Measurement is irreversible, and so is the |0⟩ RESET operation described in section 7.6.14. operation$measurement operation$|0⟩ RESET`gate-style |0⟩ RESET...