Methods and structure to probe the metal-metal interface for superconducting circuits

A method of measuring contact resistance at an interface for superconducting circuits comprising:

• using a chain structure of superconductors to measure a contact resistance at a contact between contacting superconductors;
• eliminating ohmic resistance from wire lengths in the chain structure by operating below the lowest superconducting transition temperature of all the superconductors in the chain structure,
• wherein the measurement is dominated by contact resistances of the contacts between contacting superconductors in the chain.

A contact resistance measuring device comprising:

• a chain structure of superconducting elements, the superconducting elements arranged in series to contact adjacent superconducting elements at respective contacts having respective contact resistances;
• and
• a serial resistance measuring device arranged to measure a serial resistance of the chain structure while all of the superconducting elements in the chain structure are in a superconducting state.