## Section: New Results

### Quantum optics

In [18], S. De Bièvre and his co-authors introduce a new measure of the nonclassicality of the quantum states of an optical field, the so-called “ordering sensitivity” of the state, that measures the fluctuations of its Wigner function. This work is prolonged in two subsequent papers. In [24], S. De Bièvre and the same co-authors investigate a new class of quantum states they call the “Thermal Difference States” that can be generated by parametric down conversion. They investigate in particular the degree to which such states are nonclassical. In [34], S. De Bièvre and his postdoc A. Hertz, re-interpret the ordering sensitivity in terms of another physical property of the quantum states of an optical field, namely their quadrature coherence scale. It is shown in particular that a large such coherence scale is responsible for very fast environmental decoherence of the state.