Assessing nonclassical features of optical field states : the many merits of the quadrature coherence scale

The quadrature coherence scale is a recently introduced measure of nonclassicality of states of the optical field. We analyze its properties and compare it to other well known measures of nonclassicality such as the
Wigner negative volume.

Assessing to which extent states of a single or multi-mode optical field display specific quantum features remains a subject of considerable interest. Negativity of the Wigner and/or Glauber-Sudarshan P function, entanglement, “genuine” nongaussianity, and coherence are examples of such features, each evaluated with a number of witnesses, measures and monotones.

In this talk, we will present the “quadrature coherence scale”, which provides a measure of the decoherence time of the states. We will discuss its merits, we will compare it to other nonclassicality witnesses/measures available in the literature, and we will explain how it can be directly measured (without resorting to state tomography).

The talk is based on the following publications:

• SDB, D. Horoshko, M. Kolobov, G. Patera, PRL 122, 2019; PRA 100, 2019
• A. Hertz and SDB, PRL 124, 2020
• A. Hertz, N. Cerf and SDB, PRA 102, 2020
• C. Griffet, M. Arnhem, SDB, N. Cerf, PRA 108, 2023
• A. Hertz and SDB, PRA 107, 2023
• M. Arnhem, G. Patera, and SDB, in preparation