Optimal partial estimation of quantum states from several copies
Ladislav Mišta, Jaromı́r Fiurášek · Physical Review A · 2006
We derive an analytical formula for the optimal trade-off between the mean estimation fidelity and the mean fidelity of the qubit state after a partial measurement on $N$ identically prepared qubits. We also conjecture an analytical expression for the optimal fidelity trade-off in case of a partial measurement on $N$ identical copies of a $d$-level system.