We have access to the information of everywhere almost instantaneously with countless kind of devices. We can download and transmit information from one place to another in seconds, something unimagined some decades ago. The problem today is not the amount of information that we can send/receive, neither the speed of the communication but the security of the data we want to communicate itself. A solution to this problem can be obtained by exploiting the laws of quantum mechanics. These laws allow particles, typically photons for transmitting data along optical fibers or even free-space.
Quantum Communication is one of the most promising fields of quantum physics closely related to important works such as quantum teleportation, quantum information processing and quantum cryptography. The last one turns to be the most interesting application which aims to protect information channels against eavesdropping by means of quantum cryptography.
Quantum cryptography will lead to the final solution for cyberattacks and for this reason many efforts have been dedicated to this growing field. The current protocols have been developed to exchange safe data only through a two parties’ channel (bipartite communication). Our group is actively working in the implementation of complex networks through optical fibers in order to test fundamental physics and improve current protocols of security. Very recently we have demonstrated fiber distribution of hybrid polarization-vector vortex entangled photon pairs exploiting a recently developed air-core fiber which supports OAM modes. The merging of OAM and optical fibers paves the way towards adoption of high-dimensional entanglement in quantum networks and hence to a wide range of new tests and applications.
D. Cozzolino, E. Polino, M. Valeri, G. Carvacho, D. Bacco, N. Spagnolo, L. K. K. Oxenløwe, F. Sciarrino, Air-core fiber distribution of hybrid vector vortex-polarization entangled states, Advanced Photonics, 1(4), 046005 (2019)
S. Atzeni, A.S. Rab, G. Corrielli, E. Polino, M. Valeri, P. Mataloni, N. Spagnolo, A. Crespi, F. Sciarrino, R. Osellame. Integrated sources of entangled photons at telecom wavelength in femtosecond-laser-written circuits. Optica 5, 311-314 (2018)
F. Flamini, L. Magrini, A. S. Rab, N. Spagnolo, V. D’Ambrosio, P. Mataloni, F. Sciarrino, T. Zandrini, A. Crespi, R. Ramponi, R. Osellame, Thermally reconfigurable quantum photonic circuits at telecom wavelength by femtosecond laser micromachining, Light: Science & Applications 4, e354 (2015)
G. Vallone, V. D’Ambrosio, A. Sponselli, S. Slussarenko, L. Marrucci, F. Sciarrino, P. Villoresi, Free-space quantum key distribution by rotation-invariant twisted photons, Phys. Rev. Lett. 113, 060503 (2014)
V. D’Ambrosio, E. Nagali, S. P. Walborn, L. Aolita, S. Slussarenko, L. Marrucci, F. Sciarrino, Complete experimental toolbox for alignment-free quantum communication, Nature Communications 3, 961 (2012)