Towards multi-qubit characterization with exchange-only qubits

There is growing interest in the development of encoded electron spin qubits, where multiple quantum systems (i.e., electronic spins trapped in gate-defined quantum dots (QDs)) function within a single qubit rather than individually. The exchange-only (EO) qubit, encoded as three spins in three QDs, is a promising implementation as it operates in a logical subspace that is protected from decoherence caused by global magnetic field shifts and offers fast, local, baseband control. While experiments involving multiple EO qubits in silicon have recently been demonstrated, their operational advantages come at the cost of added complexity and new error channels. For example, new leakage pathways into spin states outside the computational space must be considered in addition to more encoding-agnostic error mechanisms like charge noise and valley excitations. A comprehensive understanding of error mechanisms in the EO encoding is essential high-fidelity multi-EO qubit operations at larger scales. We report on our progress toward investigating and characterizing error mechanisms and noise sources in multi-qubit operation using the EO encoding in industrially fabricated 12 QD Si/SiGe devices from Intel.



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