Optimal Scheme for Estimating a Pure Qubit State via Local Measurements
E. Bagán, M. Baig, R. Muñoz-Tapia · Physical Review Letters · 2002
We present the optimal scheme for estimating a pure qubit state by means of local measurements on N identical copies. We give explicit examples for low N. For large N, we show that the fidelity saturates the collective measurement bound up to order 1/N. When the signal state lays on a meridian of the Bloch sphere, we show that this can be achieved without classical communication.