Complete Readout of Two-Electron Spin States in a Double Quantum Dot

Abstract

We propose and demonstrate complete spin state readout of a two-electron system in a double quantum dot probed by an electrometer. The protocol is based on repetitive single-shot measurements using Pauli spin blockade and our ability to tune on fast timescales the detuning and the interdot tunnel coupling between the GHz and sub-Hz regime. A sequence of three distinct manipulations and measurements allows establishing if the spins are in S, T_{0}, T_{+}, or T_{−} state. This work points at a procedure to reduce the overhead for spin readout, an important challenge for scaling up spin-qubit platforms.