A device that is a combination of a superconducting nanowire single-photon detector and a superconducting multi-level memory. These devices can be used to count a number of photons impinging on the device through single-photon to single-flux conversion. Electrical characterization of the device demonstrates single-flux quantum (SFQ) separated states. Optical measurements using attenuated laser pulses with different mean photon number, pulse energies and repetition rates are shown to differentiate single-photon detection from other possible phenomena, such as multiphoton detection and thermal activation. Array devices and methods are also discussed.