Experimental Property Reconstruction in a Photonic Quantum Extreme Learning Machine.

Recent developments have led to the possibility of embedding machine learning tools into experimental platforms to address key problems, including the characterization of the properties of quantum states. Leveraging on this, we implement a quantum extreme learning machine in a photonic platform to achieve resource-efficient and accurate characterization of the polarization state of a photon. The underlying reservoir dynamics through which such input state evolves is implemented using the coined quantum walk of high-dimensional photonic orbital angular momentum and performing projective measurements over a fixed basis. We demonstrate how the reconstruction of an unknown polarization state does not need a careful characterization of the measurement apparatus and is robust to experimental imperfections, thus representing a promising route for resource-economic state characterization.

Coherence-Based Operational Nonclassicality Criteria.

The nonclassicality of quantum states is a fundamental resource for quantum technologies and quantum information tasks, in general. In particular, a pivotal aspect of quantum states lies in their coherence properties, encoded in the nondiagonal terms of their density matrix in the Fock-state bosonic basis. We present operational criteria to detect the nonclassicality of individual quantum coherences that use only data obtainable in experimentally realistic scenarios. We analyze and compare the robustness of the nonclassical coherence aspects when the states pass through lossy and noisy channels. The criteria can be immediately applied to experiments with light, atoms, solid-state system, and mechanical oscillators, thus providing a toolbox allowing practical experiments to more easily detect the nonclassicality of generated states.

Machine Learning-Based Classification of Vector Vortex Beams.

Structured light is attracting significant attention for its diverse applications in both classical and quantum optics. The so-called vector vortex beams display peculiar properties in both contexts due to the nontrivial correlations between optical polarization and orbital angular momentum. Here we demonstrate a new, flexible experimental approach to the classification of vortex vector beams. We first describe a platform for generating arbitrary complex vector vortex beams inspired to photonic quantum walks. We then exploit recent machine learning methods-namely, convolutional neural networks and principal component analysis-to recognize and classify specific polarization patterns. Our study demonstrates the significant advantages resulting from the use of machine learning-based protocols for the construction and characterization of high-dimensional resources for quantum protocols.

Experimental Engineering of Arbitrary Qudit States with Discrete-Time Quantum Walks.

The capability to generate and manipulate quantum states in high-dimensional Hilbert spaces is a crucial step for the development of quantum technologies, from quantum communication to quantum computation. One-dimensional quantum walk dynamics represents a valid tool in the task of engineering arbitrary quantum states. Here we affirm such potential in a linear-optics platform that realizes discrete-time quantum walks in the orbital angular momentum degree of freedom of photons. Different classes of relevant qudit states in a six-dimensional space are prepared and measured, confirming the feasibility of the protocol. Our results represent a further investigation of quantum walk dynamics in photonics platforms, paving the way for the use of such a quantum state-engineering toolbox for a large range of applications.

Suppression law of quantum states in a 3D photonic fast Fourier transform chip.

The identification of phenomena able to pinpoint quantum interference is attracting large interest. Indeed, a generalization of the Hong-Ou-Mandel effect valid for any number of photons and optical modes would represent an important leap ahead both from a fundamental perspective and for practical applications, such as certification of photonic quantum devices, whose computational speedup is expected to depend critically on multi-particle interference. Quantum distinctive features have been predicted for many particles injected into multimode interferometers implementing the Fourier transform over the optical modes. Here we develop a scalable approach for the implementation of the fast Fourier transform algorithm using three-dimensional photonic integrated interferometers, fabricated via femtosecond laser writing technique. We observe the suppression law for a large number of output states with four- and eight-mode optical circuits: the experimental results demonstrate genuine quantum interference between the injected photons, thus offering a powerful tool for diagnostic of photonic platforms.

Nurses as seen by patients: a phenomenological study.

OBJECTIVE: during the various periods of the history of the nursing profession, many differing representations of nurses have emerged in the collective imagination. The main purpose of this study, based on a qualitative approach, has been to discover the images of the nurse that patients retain in their minds when receiving care. METHODS: 6 sound-recorded focus groups were created, made up of patients and caregivers. These persons were members of 6 associations. The recordings and observations made were then analysed by adopting a hermeneutic phenomenological approach. RESULTS: 6 themes characterising nurses emerged: Training; Between flexibility and personalisation; Organisation and nursing; Continuity in caregiving; Professional maturity; and Relations. While these themes do not provide a uniform definition for the figure of the nurse they do present the profiles that had the greatest impact on persons receiving care. CONCLUSIONS: From the experiences collected among the participants in the focus groups, no pre-defined "image" of nurses emerged, and the stereotypes and prejudices described in the literature were also not to be found. Important indications did, in any case, emerge as to the type of nurse these people want, and concerning areas which must be worked on. These indications provide valuable information that, if acted upon, might contribute to the profession's growth and improvement. In brief, there are various planes of activity upon which nurses should concentrate their efforts: training (greater specialisation), organisation (greater flexibility), and the profession (consideration of professional identity in the light of the task of meeting patients' needs).