Photoconductance quantization in a single-photon detector

We have made a single-photon detector that relies on photoconductive gain in a narrow electron channel in an ${\mathrm{Al}}_y{\mathrm{Ga}}_{1-y}\mathrm{As}/\mathrm{GaAs}$ two-dimensional electron gas. Given that the electron channel is one dimensional, the photoinduced conductance has plateaus at multiples of the quantum conductance ${2e}^2/h.\mathrm{}$ Superimposed on these broad conductance plateaus are many sharp, small, conductance steps associated with single-photon absorption events that produce individual photocarriers. This is a first step toward a photoconductive detector that could measure a single photon, while safely storing and protecting the spin degree of freedom of its photocarrier, but we have not actually achieved that goal.