542 citations · 2.8k across the 71 of their papers we have counts for
7 papers · 2 filters
Separable Measurement Estimation of Density Matrices and its Fidelity Gap with Collective Protocols
E. Bagan, M. A. Ballester, R. D. Gill +2
We show that there exists a gap between the performance of separable and collective measurements in qubit mixed-state estimation that persists in the large sample limit. We charact…
Optimal full estimation of qubit mixed states
E. Bagan, M. A. Ballester, R. D. Gill +2
We obtain the optimal scheme for estimating unknown qubit mixed states when an arbitrary number N of identically prepared copies is available. We discuss the case of states in the…
Purity estimation with separable measurements
E. Bagan, M. A. Ballester, R. Munoz-Tapia +1
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-me…
A Quantum Field Theory Twist to Photon Angular Momentum
G. F. Calvo, A. Picon, E. Bagan
A quantum field theory approach is put forward to generalize the concept of classical spatial light beams carrying orbital angular momentum to the single-photon level. This quantiz…
Relative states, quantum axes and quantum references
E. Bagan, S. Iblisdir, R. Munoz-Tapia
We address the problem of measuring the relative angle between two "quantum axes" made out of N1 and N2 spins. Closed forms of our fidelity-like figure of merit are obtained for an…
Measuring the purity of a qubit state: entanglement estimation with fully separable measurements
E. Bagan, M. A. Ballester, R. Munoz-Tapia +1
Given a finite number of copies of a qubit state we compute the maximum fidelity that can be attained using joint-measurement protocols for estimating its purity. We prove that…