Hybrid Exchange Measurement-Based Qubit Operations in Semiconductor Double Quantum Dot Qubits.

Measurement-based quantum computing (MBQC) promises natural compatibility with quantum error correcting codes at the cost of a polynomial increase in physical qubits. MBQC proposals have largely focused on photonic systems, where 2-qubit gates are difficult. Semiconductor spin qubits in quantum dots, on the other hand, offer fast 2-qubit gates via the exchange interaction. In exchange-based quantum computing, as with other solid-state qubits, leakage to higher states is a serious problem that must be mitigated. Here, two hybrid measurement-exchange schemes are proposed which quantify the benefits of MBQC on quantum dot-based quantum computing. Measurement of double quantum dot encoded qubits in the singlet-triplet basis, along with inter- and intra-qubit exchange interaction, are used to perform one and two qubit operations. Both schemes suppress individual qubit spin-state leakage errors, offer fast gate times, and require only controllable exchange couplings, up to known phase and Pauli corrections.