Fig. 3: Average phase sensing results.
From: A variational toolbox for quantum multi-parameter estimation
Semi-logarithmic plot of the Cramér-Rao bound for average phase sensing over the dephasing probability of (blue) the standard Ramsey probe and (orange) a GHZ probe. Each green dot marks the bound for a probe optimized for the particular dephasing probability. The phase shifts were fixed at the optimal spot for GHZ sensing at \({\upphi }_{j}=\frac{\pi }{6}\). We recover the optimality of the GHZ probe in the noiseless case and find improved sensing protocols in the noisy case.
