Our group performs researches, both experimental and theoretical, devoted to the investigation of entanglement in quantum mechanics and its application to quantum technologies, as quantum information processing and quantum metrology.

More in detail, many experiments based on the use of entangled pairs of photons have been performed, or are on realisation, using the eight laboratories of "Carlo Novero lab" (devoted to the memory of Carlo Novero who began this activity at IEN). Among them:

1. We have realised some experiments concerning Foundations of Quantum Mechanics. In particular, a test of Bell inequalities using the superposition of two type I PDC emissions, that allowed the generation of non-maximally entangled states. This experiment allowed a progress toward a conclusive test of local realism and permitted to exclude some specific hidden variable theory. Furthermore, some experiments were addressed to test some other specific realistic models. We also performed experiments aiming the investigation on the bounds of quantum correlation. Finally, an experiment on wave-particle duality was realised with various optical states as well. This activity has been done in part in collaboration with Turin University.

2. We contributed to the realization of the first Italian prototype of entanglement based quantum cryptography link in the framework of a national research program leaded by ELSAGDATAMAT. In this context we investigated both theoretically and experimentally quantum key distribution, and quantum secure direct communication protocols based on entangled photon pairs. We realised QKD protocols based on orthogonal states (Goldberg-Vaidman's and controfactual ones) and the controfactual one. At the moment, we are studying both quantum communication channel (fiber/open air) effects and the realisation of innovative protocols. We participate to ETSI work group on standardisation of QKD.

3. Absolute photodetectors calibration using correlated photons. Beyond studies on the traditional PDC scheme, an innovative method, based on a measurement conditional unitary gate on qubit (photon polarisation), has been developed in collaboration with Moscow University. More recently researches were performed for calibrating analog detectors.

4. Realisation and characterisation of PDC sources with specific properties, also realized in microstructured materals (such as PPLN crystals and waveguides) and study of entanglement coupling and propagation in fiber. We are also studying entanglement measures of PDC biphotons.

5. Studies and realisations of prototypes of single photon detection system with reduced deadtime exploiting multiplexing based on active optical switch (in collaboration with NIST). Characterisation of TES detectors (in collaboration with Milan University).

6. Studies on reconstruction of photon statistic and, more recently, of the full density matrix by using on/off detectors were performed in collaboration with Milan and Insubria Universities. Study on optimality of tomographic protocols and tomography of POVM.

7. We performed studies on the connection between Quantum Imaging and entanglement. We have realised for the first time a Sub-Shot-Noise Quantum Imaging experiment. These activities are performed in collaboration with Insubria and Milan Universities.

8. From a theoretical side we worked on multidimensional QKD and studied application of mesons to local realism tests.