# Special Issue on Quantum Optics for Fundamental Quantum Mechanics
###### Abstract  
In this paper, we investigate the quantum mechanics of quantum mechanics with a quantum mechanical property. We show that the quantum mechanics of quantum mechanics is a quantum mechanical property. introducing the concept of quantum non-locality, one of the most intriguing and fascinating facets of quantum mechanics, which, at the same time, remains one of the most significant problems due to the absence of its deep understanding. In the paper [10] that celebrates the recent 90 th anniversary of the emergency of the uncertainty principle, a pillar of quantum theory, the authors report the latest experimental results of uncertainty relations, quantified in terms of Shannon entropies, focusing in particular on outcomes in neutron optics and on the type of measurement uncertainties that describe the inability to obtain respective individual results from joint measurement statistics. Superfluids, fluctuations and disorder are the topics discussed in [11], where a field-theory description of ultra-cold bosonic atoms in the presence of a disordered external potential is described: the authors investigate and review the interplay between disordered energy landscapes and fluctuations, both thermal and quantum ones, by means of functional integration techniques. The last review paper [12] deals with topological qubits and their potential to form from the so-called winding number superpositions, where the winding number is a topologically significant quantity valuable for applications in various areas of mathematical physics, and of the consequent possibility to use these qubits as carriers of quantum information in linear optical systems, the most common realm for quantum communication. The arguments covered in the previous section are then developed in the research articles, which consist of eight papers, offering a panorama of the present studies in quantum optics and analyzing some specific issues of the different lines of research in which this field is structured. In summary, issues concerning non-locality studies range from the application of the de Broglie-Bohm model to Gauss-Maxwell beams [13] to revisiting complementarity relations in bipartite quantum systems [14]; correlations in atoms are investigated in [15; 16], photon emission and statistics in [17; 18] and methods in quantum technologies in [19; 20]  
The first paper [13] of this section deals with a Bohmian-based approach to Gauss-Maxwell beams, a particularly appropriate and natural tool in optical problems dealing with Gaussian beams acted or manipulated by polarizers: a hydrodynamic-type extension of such a formulation is provided and discussed, complementing the notion of the electromagnetic field with that of (electromagnetic) flow or streamline. The described features confer the approach a potential interest in the analysis and description of single-photon experiments. The complementarity relations in bipartite quantum systems are revisited in paper [14], where, by focusing on continuous-variable systems, the authors examine the influential class of EPR-like (EPR: Einstein Podolsky Rosen) states through a generalization to Gaussian states and introduce some new quantitative relations between entanglement and local interference within symmetric and asymmetric double-double-slit scenarios. In the paper, this approach is then related to ancilla-based quantum measurements and specifically to the paradigm of weak measurements. In papers [15; 16], the attention moves to the investigation of correlations in atomic systems. In fact, in [15], the Electromagnetically Induced Transparency (EIT), a coherent optical nonlinear effect, is analyzed by treating the weak probe field as a perturbation to the strong coupling fields in the atomic system and using the perturbative method in a master equation: the authors show how the features of the linear response of EIT phenomena can be uniformly demonstrated, regardless of the details of atomic energy-level configuration.