Fig. 1.

Silicon double quantum dot with latched Pauli spin blockade readout. a False-colored scanning electron micrograph of the device architecture. Dots are created under G1 and G2 electrodes and situated in the centre of the confinement gap. Scale bar is 200 nm. b Cross section illustrating dots under G1 and G2, which are tunnel-coupled with fast and slow tunnel rates Γ_Fast and Γ_Slow to an electron reservoir under gate ST. This reservoir is located on the drain (D) side of the sensor. c Cyclic pulsing^19,28 (arrows) through sequence A(0, 1)-B(1, 1)-C, where the location of point C is rastered to form the image, reveals latched spin blockade features (orange dot & top zoom-in). Shown is the differential transconductance d(ΔI_SET)/d(ΔV_G1), where ΔI_SET is the difference in SET current recorded at points B and C. d When point B lies in the (0, 2) charge region, no blockade is observed, as expected for an initial singlet state. e Observation of state-latching of the G2 dot is due to weak coupling to the reservoir. In order to populate the (1, 2) state, the existing (1, 1) state must co-tunnel via (0, 2) where PSB exists. If the state is not blocked (i.e. the $∣S⟩$ state) then an electron is free to tunnel from the reservoir to fill G1. Otherwise, the tunnelling from the reservoir is blocked, resulting in a spin-to-reservoir charge state conversion. f Histogram of ΔI_SET recorded at Standard-PSB readout location indicated by the blue marker on map d. g Histogram of ΔI_SET recorded at Latched-PSB readout location for B(1, 1) (orange) and B(0, 2) (red); there is a clear increase in sensitivity provided by the Latched-PSB readout