Study of the Signal to Noise Ratio of a Double-Dot Magnetic Detector

Sometime ago we proposed a device based on a double dot which can also be operated as a position or magnetic field sensor. The device consists of a cavity defined in a high-mobility 2-dimensional electron gas with an input and an output constriction and a potential barrier exactly in the middle, partitioning it into two identical dots. As a result of the symmetries of the trajectories, a very strong conductance enhancement (with respect to the conductance associated with the barrier alone) is observed, over a wide energy range. This effect can be suppressed as a result of the symmetry-breaking effect of an applied magnetic field. Here we perform a detailed study of the signal to noise ratio that can be achieved and therefore of the minimum measurable magnetic field, taking into account the contributions of flicker, thermal and shot noise components. We observe that the main limitation to the achievable sensitivity is that due to flicker noise.