Quantum measurements on finite dimensional systems: relabeling and mixing
: Haapasalo E, Heinosaari T, Pellonpaa JP
Publisher: SPRINGER
: 2012
: Quantum Information Processing
: QUANTUM INFORMATION PROCESSING
: QUANTUM INF PROCESS
: 6
: 11
: 6
: 1751
: 1763
: 13
: 1570-0755
DOI: https://doi.org/10.1007/s11128-011-0330-2(external)
: https://research.utu.fi/converis/portal/detail/Publication/2781628(external)
Quantum measurements are mathematically described by positive operator valued measures (POVMs). Concentrating on finite dimensional systems, we show that one can limit to extremal rank-1 POVMs if two simple procedures of mixing and relabeling are permitted. We demonstrate that any finite outcome POVM can be obtained from extremal rank-1 POVMs with these two procedures. In particular, extremal POVMs with higher rank are just relabelings of extremal rank-1 POVMs and their structure is therefore clarified.