1. An apparatus comprising: a first electrode; a second electrode; a nano-scale channel between the first electrode and the second electrode wherein the nano-scale channel has a first state in which an electrical impedance of the nano-scale channel is relatively high and a second state in which the electrical impedance of the nano-scale channel is relatively low; dielectric adjacent the nano-scale channel; and a gate electrode adjacent the dielectric configured to control a threshold number of quanta of photo-stimulus; wherein the nano-scale channel is configured to switch between the first state and the second state in response to an application of a quantum of photo-stimulus above the threshold number of quanta of photo-stimulus.