Absence of Quantum-Electrodynamic Corrections to the Charge of the Electron as Measured in Josephson Junction Experiments

The ac Josephson effect enables one to measure the ratio Δμh, where Δμ is the electrochemical potential difference between two weakly coupled superconductors. Combined with an independent measurement of the electrostatic potential difference V, this measurement determines the ratio e/h. This determination rests on the fact that a voltage difference is defined so that the electrochemical potential difference is Δμ=eV, where e is the charge on the free electron. Further, while we argue that it is not directly relevant to the determination of e/h, there are no quantum-electrodynamic corrections to the electrostatic term in the chemical potential difference Δμ.