Characterization of Multiple Qubit Encodings in Industrially-Manufactured Silicon Quantum Dots

Silicon-based spin qubits in lithographically defined quantum dots (QDs) are a promising platform for quantum computing due to their ability to use established silicon growth and processing technologies. These devices are operated using a variety of different qubit encodings that may have distinct advantages and disadvantages. Here, we explore two encodings that utilize baseband pulsing techniques to provide localized control of single qubits. The singlet-triplet encoding requires two electrons and two QDs with universal single-qubit control accomplished by evolution of the state in the presence of a magnetic field gradient between electron spins and the exchange interaction. In contrast, the exchange-only encoding provides universal single-qubit control through only the modulation of the exchange interaction, at the cost of requiring three electrons and three QDs and introducing additional leakage states. We present experimental realizations of both encodings in a single isotopically enriched, industrially-manufactured Si/SiGe quantum device. We characterize and compare operation of the different encodings to weigh their advantages and disadvantages for quantum computation.