Extended Data Fig. 3: Error modelling for GHZ-state fidelities.
From: Multi-qubit gates and Schrödinger cat states in an optical clock
a, Sensitivity of multi-qubit gate \(\widehat{{\mathcal{U}}}\) to Rydberg Rabi frequency and detuning deviations for various Nmax. Solid lines indicate infidelity for N = Nmax GHZ state; dashed lines indicate infidelity for N = 2 Bell state. b, Modelling of various error sources for N = 2 Bell state (blue) and N = 4 GHZ state (red, hatched). For the Bell state, we consider the CZ gate protocol shown in Fig. 1c; for the four-atom GHZ state, we consider the general Nmax = N scheme shown in Fig. 2a. The measurement-corrected Bell state (four-atom GHZ state) infidelity (see Extended Data Table 2) is shown as the blue dashed (red dotted) line. In both cases, our error model accounts for roughly a third of the observed infidelity. The presence of pulse discretization/rise time error for only the Bell state is because we use the exact time-optimal CZ gate implementation described in ref. 11 as opposed to a modulation optimized for our pulse model.
