Scalable photon number resolving photon detector

A method for operating a photon counting device, comprising:

• applying a bias current to a unit cell, the unit cell comprising:
• one or more photodetectors;
• a current dynamics control element coupled in series with the one or more photodetectors, the current dynamics control element being adapted for a predefined relaxation time of the unit cell;
• and
• a transistor having a superconducting gate element that is coupled in parallel with the one or more photodetectors and a channel element that is electrically insulated from the superconducting gate element via a thermally-conductive component composed of a non-superconducting material;
• maintaining a temperature of one or more superconducting components in the one or more photodetectors and a temperature of the superconducting gate element in the transistor below a threshold temperature;
• and
• in response to a photon being incident upon a photodetector of the one or more photodetectors:
• transitioning, by the one or more superconducting components in the photodetector upon which the photon is incident, from a superconducting state to a non-superconducting state;
• redirecting at least a portion of the bias current from the one or more photodetectors to the superconducting gate element of the transistor;
• and
• transitioning, by the superconducting gate element of the transistor, from the superconducting state to the non-superconducting state, wherein while the superconducting gate element is in the non-superconducting state, heat generated by the superconducting gate element is transferred to the channel element causing the channel element to have an increased resistance.

A photon-number resolving detector, comprising:

• a plurality of photon detecting units coupled in series, each respective photon detecting unit of the plurality of photon detecting units comprising:
• one or more superconducting photodetectors;
• a current dynamics control element coupled in series with the one or more superconducting photodetectors;
• and
• a gate of an impedance amplifier coupled in parallel with the one or more superconducting photodetectors of the respective photon detecting unit;
• a readout line coupled to output channels of the impedance amplifiers of the plurality of photon detecting units, wherein each respective output channel is coupled to a corresponding gate via a thermally-conductive component composed of a non-superconducting material, and wherein heat generated by the corresponding gate is transferred to the respective output channel causing the respective output channel to have an increased resistance;
• and
• a second circuit coupled to the readout line.