2003/09/30 by Hui Li, Jiangfeng Du · 2 citations
Computer Science · Physics and Astronomy · #Atomic and Subatomic Physics Research #Quantum Information and Cryptography #Quantum optics and atomic interactions #quant-ph
paper · pdf · doi:10.1103/physreva.70.012111
published as Phys. Rev. A 70, 012111 (2004) · 5 pages, 1 figure
openalex publication_date 2004/07/29 · arxiv created 2004/07/30 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
The purity of a reduced state for spins that is pure in the rest frame will most likely appear to degrade because spin and momentum become mixed when viewed by a moving observer. We show that such a boost-induced decrease in spin purity observed in a moving reference frame is intrinsically related to the spatial localization properties of the wave package observed in the rest frame. Furthermore, we prove that, for any localized pure state with separable spin and momentum in the rest frame, its reduced density matrix for spins inevitably appears to be mixed whenever viewed from a moving reference frame.