A multiple arrayed parallel nanowire device includes one or more arrays connected in series, wherein each array includes a plurality of narrow nanowires flanked by one or more wide nanowires, a top electrode, an applied current, a bottom ground electrode, and one or more lateral electrodes where one or more currents or one or more probing voltages can be applied to detect voltage changes in each array. The device detects single and multiple photons without destroying superconductivity in all the nanowires in the array and is thus capable of remaining sensitive to subsequent photon impacts. Moreover, the device can resolve the location of each photon impact.

A superconducting thin film having excellent critical current characteristics is provided. A substrate for a superconducting thin film includes a substrate body (10A) having a main surface (10B) in which the root mean square slope Rq of a roughness curve is 0.4 or less.