Automated Tuning of Interdot Coupling for Pauli-Spin Blockade Readout

Scaling up quantum dot based spin qubits to multi-qubit arrays requires automated routines capable of setting appropriate charge configurations, tunnel rates, quantum state readout, and coherent manipulations all without user input. Decoherence-free subspace (DFS) and singlet-triplet qubits often employ Pauli Spin Blockade (PSB) to distinguish singlet and triplet states, but the fidelity of this readout method can suffer from incomplete charge relaxation and non-equilibrium charge states. In this talk, we present progress toward an automated method for setting the tunnel rate between two quantum dots used for PSB readout which ensures appropriate charge relaxation prior to measurement. By defining a fast pulse sequence and an adiabatic pulse sequence which both traverse the detuning boundary between the dots, it is possible to identify a lower bound on the charge relaxation rate at a given interdot coupling. Dot coupling is then adjusted to ensure that charge relaxation occurs on much faster timescales than the readout time. Our work suggests a path forward for automated tune-up of singlet-triplet readout applicable across many types of spin qubits.