[en] We consider the problem of identifying the quantum spin states that are the optimal sensors of a given transformation, averaged over all possible orientations of the spin system. Our geometric approach to the problem is based on a fidelity criterion and is entirely general, encompassing any unitary transformation. This formalism leads to a universality result: For any value of the spin, there exists a zero-measure subset of states that can be the optimal sensors for certain transformations and the worst sensors for others, and this set does not depend on the transformation under consideration. In other words, some spin states are simply the best (or worst) sensors, regardless of what they detect.
Disciplines :
Physics
Author, co-author :
Aragón-Muñoz, Luis; Institute for Nuclear Sciences (UNAM)
Chryssomalakos, Chryssomalis; Institute for Nuclear Sciences (UNAM)
Gabriela Flores-Delgado, Ana; Institute for Nuclear Sciences (UNAM)
Martin, John ; Université de Liège - ULiège > Département de physique > Optique quantique
Serrano Ensástiga, Eduardo ; Université de Liège - ULiège > Complex and Entangled Systems from Atoms to Materials (CESAM)
Language :
English
Title :
Universality in fidelity-based quantum metrology
Publication date :
03 September 2026
Journal title :
Physical Review. A, Atomic, molecular, and optical physics
ISSN :
1050-2947
eISSN :
1094-1622
Publisher :
American Physical Society, United States - Maryland
Volume :
114
Pages :
032406
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
ULiège - University of Liège F.R.S.-FNRS - Fonds de la Recherche Scientifique EOS - The Excellence Of Science Program
Funding number :
EOS project 40007526
Funding text :
Financial support is acknowledged, in the form of a SECIHTI (Mexico) postdoctoral fellowship (LFAM), a SECIHTI SNI assistantship (AGFD) and the SECIHTI CBF-2025-I-676 and DGAPA-PAPIIT-UNAM IN112224 projects (LFAM, CC, AGFD). ESE acknowledges support from the postdoctoral fellowship of the IPD-STEMA program of the University of Liège (Belgium). JM and ESE acknowledge the FWO and the F.R.S.-FNRS for their funding as part of the Excellence of Science program (EOS project 40007526).
