- This is related to my previous question:
The current most promising candidate for quantum computing are superconducting circuits, Transmon for example. One problem with Transmon, an anharmonic oscillator, is the leakage to higher energy levels when trying to drive it with short microwave pulses. As shorter pulses have larger bandwidth.
I wonder if there exists quantum circuits that are two-level? If not, what is the fundamental reason that hinders their existence?