An elongated quantum dot as a distributed charge sensor

Elongated quantum dots have been explored as a way to mediate a spin-spin interaction between spatially separated semiconductor quantum dots. Increasing the separation between quantum dots has potential advantages for the scalability of dense two-dimensional arrays, in gate routing and the integration of sensors and reservoirs. Here, we study a metal-oxide-silicon (MOS) device where two quantum dot arrays are separated by an elongated quantum dot (340 nm long, 50 nm wide). We monitor charge transitions of the elongated quantum dot by measuring radiofrequency single-electron currents to a reservoir to which we connect a lumped-element resonator. This elongated `single electron box' is used to achieve charge sensing of remote quantum dots in each array, separated by a distance of over 0.5 μm. Simultaneous charge detection on both ends of the elongated dot demonstrates that the charge is well distributed across its nominal length, supported by the simulated quantum-mechanical electron density. Our results illustrate how single-electron boxes can be realised with versatile footprints to enable compact qubit processors, offering remote sensing as well as the possibility of mediated coupling.