9.1 So many gates …
In practice, a hardware quantum computer implements a core set of primitive gates and the others are built from them using circuits. These core operations may be among the ones we saw in the last chapter or they may be much stranger looking: any 2 by 2 unitary matrix can be considered a 1-qubit gate.
The primitive gates depend on the technology used to create the physical quantum computer. More advanced gates are then built from these primitive gates. The Qiskit open source quantum computing framework, for example, provides a large selection of gates you can use, many of them built from the core ones. [16]
At the hardware level, experimental physicists and engineers work to optimize the core gates. Above that, other physicists and computer scientists try to create the best performing higher-level gates.
In the classical case, machine code is extremely low level and directly instructs the processor. Above that is assembly code, which abstracts...
