Fig. 1: Holevo and Nagaoka–Hayashi bounds for estimating multiple orthogonal rotation parameters simultaneously. | npj Quantum Information

Fig. 1: Holevo and Nagaoka–Hayashi bounds for estimating multiple orthogonal rotation parameters simultaneously.

From: Efficient computation of the Nagaoka–Hayashi bound for multiparameter estimation with separable measurements

Fig. 1

For a maximally entangled two-qubit probe under the action of the phase damping channel, we plot the Holevo bounds (solid lines) and Nagaoka–Hayashi bounds (dashed lines) in terms of average preciseness for estimating two (blue) and three (red) orthogonal rotation parameters simultaneously. The Nagaoka–Hayashi bounds can be achieved by a separable measurement on a single probe, while the Holevo bound requires a collective measurement on a possibly infinite number of copies. The shaded area shows the gap between the two bounds. For estimating a single parameter, the Holevo and Nagaoka–Hayashi bounds coincide and are equal to the two-parameter Holevo bound.

Back to article page