Photon number resolving superconducting detector

A method of resolving a number of co-incident photons, comprising:

• optically coupling a waveguide to a superconducting wire having a plurality of alternating narrow and wide portions;
• electrically coupling the superconducting wire to a current source;
• electrically coupling an electrical contact in parallel with the superconducting wire, wherein the electrical contact has a resistance that is less than a resistance of the superconducting wire while at least one narrow portion of the superconducting wire is in a non-superconducting state;
• providing a first current from the current source to the superconducting wire, the first current configured to maintain the superconducting wire in a superconducting state in the absence of incident photons;
• receiving one or more photons via the waveguide;
• measuring an electrical property of the superconducting wire, wherein the electrical property is proportional to a number of photons incident on the superconducting wire;
• and
• determining the number of photons incident on the superconducting wire based on the electrical property.