Fig. 2: Quantum dot tuning for cascade-based readout.

Numbers in round brackets indicate charge occupations of the dots. a Charge-stability diagram with transitions for dots 1 and 2. The white, dashed trapezoid on the top-left side of the inter-dot is the Pauli spin blockade (PSB) readout region. The black dots indicate the voltages for the PSB readout cycle: E(mpty), L(oad) and R(ead). b Charge-stability diagram similar to a, but with different occupations of the rightmost dot. The white, dotted trapezoid is the cascade Pauli spin blockade (CPSB) readout region. White and black dots labelled with E\(^{\prime}\), L\(^{\prime}\) and R\(^{\prime}\) indicate the pulse positions for the CPSB readout cycle. Note that the voltages at the origin are different from those in a. c Charge-stability diagram showing both the charge states for PSB and CPSB readout. Dashed (dotted) lines correspond to the charge transitions for the PSB (CPSB) readout regions. d Ladder diagram illustrating the alignment of the dot electrochemical potentials for the CPSB at the readout point. For a triplet state, the system remains in (1101) (red), whereas for a singlet state it transitions to (0201) and then (0200) (green).