[en] Coherent and anticoherent states of spin systems up to spin j=2 are known to be optimal in order to detect rotations by a known angle but unknown rotation axis. These optimal quantum rotosensors are characterized by minimal fidelity, given by the overlap of a state before and after a rotation, averaged over all directions in space. We calculate a closed-form expression for the average fidelity in terms of anticoherent measures, valid for arbitrary values of the quantum number j. We identify optimal rotosensors (i) for arbitrary rotation angles in the case of spin quantum numbers up to j=7/2 and (ii) for small rotation angles in the case of spin quantum numbers up to j=5. The closed-form expression we derive allows us to explain the central role of anticoherence measures in the problem of optimal detection of rotation angles for arbitrary values of j.
Research center :
CESAM - Complex and Entangled Systems from Atoms to Materials - ULiège
Disciplines :
Physics
Author, co-author :
Martin, John ; Université de Liège - ULiège > Département de physique > Optique quantique
Weigert, Stefan; Department of Mathematics, University of York, UK-York YO10 5DD, United Kingdom
Giraud, Olivier; Université Paris-Saclay, CNRS, LPTMS, 91405 Orsay, France
Language :
English
Title :
Optimal Detection of Rotations about Unknown Axes by Coherent and Anticoherent States
Publication date :
16 June 2020
Journal title :
Quantum
eISSN :
2521-327X
Publisher :
Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften, Austria
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