Separable Measurement Estimation of Density Matrices and its Fidelity Gap with Collective Protocols

2005/12/31 by E. Bagán, E. Bagan, M. A. Ballester +7
Computer Science · Physics and Astronomy · #Quantum Computing Algorithms and Architecture #Quantum Information and Cryptography #Quantum Mechanics and Applications #quant-ph

paper · pdf · doi:10.1103/physrevlett.97.130501

published as Phys. Rev. Lett. 97, 130501 (2006) · version published in PRL

arxiv created 2006/09/25 · openalex publication_date 2006/09/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/04

Abstract

We show that there exists a gap between the performance of separable and collective measurements in the qubit mixed-state estimation that persists in the large sample limit. We characterize the gap with sharp asymptotic bounds on mean fidelity. We present an adaptive protocol that attains the separable measurement bound. This protocol uses von Neumann measurements and can be easily implemented with current technology.

Citations

• Average fidelity between random quantum states
• Explicit computation of the Bures distance for density matrices
• Estimating the spectrum of a density matrix with LOCC