Approaching linear photon-number resolution with superconductor nanowire array

Linear photon-number resolution is the key to quantum tomography. However, it is difficult to realize ideal linear photon-number resolution through multi-pixel technology because of the lack of detectors with both an ultrahigh quantum efficiency and infinite pixel number. In this letter, a photon-number-resolving detector approaching linear resolution is demonstrated. The detector is composed of 16 niobium nitride nanowires (4 × 4 on the chip) driven by independent readouts. The parallel readout enables all pixels to register incident photons independently and efficiently. The experimental results indicate that the amplitudes of the output pulse signals after being combined are linearly proportional to the number of detected photons, and the maximum number of resolved photons reaches 16. The mean photon-number distribution μ = 0.5, 2.2, 3.5, and 5.5 in a laser pulse approximates an ideal Poisson distribution, which indicates that this detector approaches linear resolution. Moreover, the spatial distribution of light can be illustrated by the array device, and the result is consistent with the theoretical prediction.