Probably the experiment most students are familiar with, which "switches operators" (i..e changes what is being measured) at the quantum scale would be the Stern Gerlach experiment, where more than one S-G apparatus is used. Rotating the apparatus 90deg changes the operator from z-spin to y-spin.
Pretty much every experiment involves changing operators.
i.e. to do experiments on a particle in a box, first you have to get the particle in the box. The act of putting it in the box is a measurement of it's position - to "someplace inside the box" ...
In an experment, you don't think "I'll switch operators from momentum to hamiltonian", you think "I'll measure momentum then energy". You are just changing what you want to measure. Physically it involves changing the apparatus used to do the measurement.
Atoms have had something like 4 measurements - to prepare them in a definite quantum state: this is why you have 4 quantum numbers.
The experiments would involve hyperfine splitting for eg.