Fig. 3
From: High-fidelity entangling gate for double-quantum-dot spin qubits
Entangling gate. a To entangle the qubits, we perform a simultaneous rotary echo on both for a varying total length of time t, followed by tomographic readout to reconstruct the two-qubit density matrix. b Bloch vector length for qubit 1, l 1, during the entangling gate as the phase between rf drives varies. Nodes in l 1 denote entanglement. The entanglement rate vanishes when the qubits are driven 90° out of phase. c Concurrence vs. time for the entangling gate. Positive values of concurrence indicate entangled states. Negative values of concurrence indicate decoherence. The solid red line is a theoretical simulation taking into account hyperfine and low- and high-frequency charge noise (see Supplementary Information). d Single-qubit Bloch vector lengths l 1 and l 2 during joint evolution. When the qubits are detuned from each other, the interaction vanishes
