TY - JOUR
T1 - Purity estimation with separable measurements
AU - Muñoz-Tapia, R.
AU - Romero-Isart, O.
AU - Ballester, M. A.
AU - Bagan, E.
PY - 2005/9/9
Y1 - 2005/9/9
N2 - Given a large number N of copies of a qubit state of which we wish to estimate its purity, we prove that separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This shows that the optimal estimation of the entanglement of a two-qubit state can also be achieved asymptotically with fully separable measurements. Thus, quantum memories provide no advantage in this situation. The relationship between our global Bayesian approach and the quantum Cramér-Rao bound is discussed. © 2005 The American Physical Society.
AB - Given a large number N of copies of a qubit state of which we wish to estimate its purity, we prove that separable-measurement protocols can be as efficient as the optimal joint-measurement one if classical communication is used. This shows that the optimal estimation of the entanglement of a two-qubit state can also be achieved asymptotically with fully separable measurements. Thus, quantum memories provide no advantage in this situation. The relationship between our global Bayesian approach and the quantum Cramér-Rao bound is discussed. © 2005 The American Physical Society.
UR - https://dialnet.unirioja.es/servlet/articulo?codigo=1295282
U2 - 10.1103/PhysRevLett.95.110504
DO - 10.1103/PhysRevLett.95.110504
M3 - Article
SN - 0031-9007
VL - 95
JO - Physical Review Letters
JF - Physical Review Letters
M1 - 110504
ER -