Fig. 4: High-fidelity two-qubit gate.
From: Quantum logic with spin qubits crossing the surface code threshold
a, A sequence of pulses generated by the arbitrary waveform generators in an example GST sequence. The purple waveforms show the in-phase component of X/Y gates. The CZ gate is indicated by the orange pulse of gate B and the blue and red compensation pulses of gate LP and gate RP. b, Experimentally determined PTM of a CZ gate. The colour code is the same as in Fig. 2. c, Left, the quantum circuit used to reconstruct the Bell state \(|{\Psi }^{+}\rangle =(|01\rangle +|10\rangle )/\sqrt{2}\) based on the corresponding PTMs. Right, the real part of the reconstructed density matrix of the |Ψ+⟩ state. The colour code is the same as in Fig. 2, except that red (blue) bars here are theoretically +0.5 (−0.5).
