Fig. 3: Polar plot of the experimentally observed (and rescaled) variances.
From: Retrodiction beyond the Heisenberg uncertainty relation
a Measured \(({\rm{Var}}({m}_{2}| {m}_{1})-\frac{1}{2})/{\kappa }_{2}^{2}\) (blue) and \(({\rm{Var}}({m}_{2}| {m}_{1},{m}_{3},{m}_{4})-\frac{1}{2})/{\kappa }_{2}^{2}\) (red) for the Faraday probing of atomic quadratures \({\hat{x}}_{\text{A}}(\theta )\). The data are obtained with optical probe pulse durations corresponding to coupling strengths \({\kappa }_{1}^{2}=1.7\), \({\kappa }_{2}^{2}=0.81\), \({\kappa }_{3}^{2}=3.3\) and \({\kappa }_{4}^{2}=2.2\) between the atoms and the field. A value of 1/2 corresponds to the standard quantum limit (SQL) for the atomic spin variance. b Zoom-in of the red curve in (a). The shaded error bar (one standard deviation) is derived from 5 identical experiments, each consisting of 10,000 repetitions of the pulse sequence.
