8.5 Summary

This chapter introduced the standard 2-qubit and 3-qubit gate operations to complement the classical forms from section 2.4. The CNOT / X and CZ gates allow us to entangle qubits. Entanglement, along with superposition and interference, is essential in quantum computing.

Our cat-in-the-box was translated into quantum terms and got its own circuit.

Now that we have a collection of gates, it’s time to put them into circuits and implement algorithms. We begin doing that in the next chapter. In section 9.3, we will see how we can create any quantum gate by combining others, at least to a very close approximation. This extends our discussion of logic gate universality in section 2.4.