Two-axis Control and Readout of an Exchange-Only Spin Qubit in a GaAs Triple Quantum Dot*

The initialization, full control, and readout of a GaAs triple quantum dot exchange qubit is demonstrated. Appropriate depletion gate design has enabled control and single-shot readout along multiple Bloch sphere axes in a three electron device. Rotations around both non-orthogonal control axes are projected along three separate Bloch sphere axes, and quality factors $(Q \equiv \omega / T_2^*)$ of 500 are observed. Finally, we analyze decoherence and dynamical decoupling schemes unique to this system.