Parametrization of spin-1 classical states

Olivier Giraud (1) , Petr Braun (2, 3) , Daniel Braun (4)

1 LPTMS - Laboratoire de Physique Théorique et Modèles Statistiques
2 Institute of Physics [Saint-Petersburg]
3 Fachbereich Physik [Duisburg]
4 ICQ - Cohérence Quantique (LPT)

We give an explicit parametrization of the set of mixed quantum states and of the set of mixed classical states for a spin--1. Classical states are defined as states with a positive Glauber-Sudarshan P-function. They are at the same time the separable symmetric states of two qubits. We explore the geometry of this set, and show that its boundary consists of a two-parameter family of ellipsoids. The boundary does not contain any facets, but includes straight-lines corresponding to mixtures of pure classical states.

Domaines: Gaz Quantiques [cond-mat.quant-gas]; Physique Quantique [quant-ph]

Olivier Giraud, Petr Braun, Daniel Braun. Parametrization of spin-1 classical states. Physical Review A : Atomic, molecular, and optical physics [1990-2015], 2012, 85 (3), pp.032101. ⟨10.1103/PhysRevA.85.032101⟩. ⟨hal-00681035⟩