Pauli Spin Blockade — Quantum Dot Qubit Spin Readout

A double quantum dot traps two electrons, one per dot. Prepare their joint spin state as a singlet or one of three triplets, then fire a readout pulse: the simulator sweeps the interdot detuning toward the (0,2) charge configuration where both electrons would share one dot. Pauli exclusion only allows the spin-antisymmetric singlet to make that move — every triplet is Pauli-blocked and stays put — so a capacitively-coupled charge sensor reading the dots' electron count becomes a real, if imperfect, single-shot spin readout. Tunnel coupling, pulse duration and a spin-orbit/hyperfine leakage rate are all adjustable, and a running fidelity counter shows how leakage caps real-world readout accuracy — exactly the trade-offs behind singlet-triplet spin-qubit readout in real quantum-dot devices.