Superconducting-qubit electrometry
Charge-sensitive superconducting levels shift with electric environment.
$$H=4E_C(n-n_g)^2-E_J\cos\varphi$$
Physical intuition
Charge-sensitive superconducting levels shift with electric environment.
Deep dive: physical mechanism
Gate charge changes the circuit Hamiltonian, and spectroscopy or dispersive readout converts that shift into a signal.
What is measured experimentally?
Frequency or phase shifts reveal offset charge or nearby charge motion.
Assumptions, noise and limitations
Charge noise and quasiparticles may overwhelm the desired signal.
Research and simulation exercise
Calculate charge dispersion versus EJ/EC for a simplified Cooper-pair box.
Connect the ideas
Explore the chapter overview, learning path, and references.