Dispersive readout of spin blockade in a carbon nanotube double quantum dot

We probe the charge states of a carbon nanotube double quantum dot by coupling superconducting resonators to the leads and a gate of a device designed for operation as a spin-valley qubit. Multiplexed dispersive readout allows rapid reflectometry measurements of the device without the need for dedicated proximal charge sensors. In this way as-grown nanotubes may be used in a bottom-gated geometry to create low-disorder devices that are freely suspended and then insulated using atomic layer deposition. These techniques are demonstrated with measurements in the spin blockade regime. We acknowledge support from IBM, NSF-MWN, NSF-NRI through the INDEX Center, and Harvard University.