ANDREA GERALDI

PhD Graduate

PhD program:: XXXIII



Thesis title: Experimental study of anomalous diffusion and quantum correlations in an all optical quantum walk

In recent years, quantum walks (QWs), the quantum counterpart of classical random walks (CRWs), have become increasingly attractive for quantum information fields, ranging from quantum computation, to quantum simulation, and quantum cryptography. Furthermore, QWs have been found to be a useful resource for the study of energy propagation and transport phenomena. Indeed, QWs are featured by a variance of the position probability distribution of the walker which grows quadratically with the number of the step, namely σ^2 = α*n^2. This behavior is usually referred to as ballistic. Several natural propagation phenomena follow an anomalous diffusion regime, for which it holds σ^2 = α*n^β with 1 < β < 2 (β < 1) in the superdiffusive (subdiffusive) case. Being it an intermediate regime between the ballistic and the diffusive one, which is typical of CRWs, it is natural to ask whether QWs allow to reproduce such a behavior. The aim of this thesis work consists in studying this possibility by experimentally investigating anomalous diffusion within a QW framework, exploiting both single and two photons evolution. The superdiffusive dynamics has been investigated by adopting a novel bulk optics scheme, whose basic idea has been used in the study of non-Markovian dynamics. By adopting the so-called p-diluted disorder, we could investigate the average dynamics of a quantum particle moving in a random environment. We found that, in both cases of single and two walkers, the evolution is characterized by a superdiffusive behavior, with the value of the parameter β depending on the disorder level experienced by the walkers. Subdiffusivity has been studied by means of a time-split QW. A static disorder, namely a disorder fixed in time but varying in space, can reproduce the so-called Anderson localization, consisting of an exponential localization of the walker around its starting position. By perturbing it through the p-diluted disordering technique, it is possible to break the static condition giving rise to Anderson localization. We found that in this case a clear subdiffusive behavior can be obtained, with a value of β increasing with the disorder level and reaching β = 1 when the disorder is maximum. These results demonstrate that QWs provided with the p-diluted disorder are feasible resources to study anomalous diffusion processes, for both single and two photons cases, and that it can be helpful in shedding light on the physical mechanisms underlying anomalous diffusion phenomena. Secondarily, by the same disordering technique, we studied how to quantify non-classical correlations due to indistinguishability between two walkers, by investigating the violation of a certain inequality, as a function of the disorder experienced by the photons during their evolution. Simulated and experimental results show that the disorder can control the non-classical correlation between the photons travelling along different pairs of modes. Moreover, we show that, by properly tuning the disorder, it is possible to retrieve a relevant amount of the non-classical correlation initially present between the walkers, which would be otherwise decreased by on ordered QW evolution. This suggests that this technique could be adopted as a useful tool in a quantum protocol scenario, such as for instance metrology.

Research products

11573/1638501 - 2022 - Experimental multi-state quantum discrimination through optical networks
Laneve, A.; Geraldi, A.; Hamiti, F.; Mataloni, P.; Caruso, F. - 01a Articolo in rivista
paper: QUANTUM SCIENCE AND TECHNOLOGY (Bristol : IOP Publishing) pp. 025028- - issn: 2058-9565 - wos: WOS:000772648200001 (1) - scopus: 2-s2.0-85128387926 (1)

11573/1540348 - 2021 - Transient subdiffusion via disordered quantum walks
Geraldi, Andrea; De, Syamsundar; Laneve, Alessandro; Barkhofen, Sonja; Sperling, Jan; Mataloni, Paolo; Silberhorn, Christine - 01a Articolo in rivista
paper: PHYSICAL REVIEW RESEARCH (College Park MD: American Physical Society) pp. - - issn: 2643-1564 - wos: WOS:000641043900005 (10) - scopus: 2-s2.0-85114370492 (10)

11573/1618502 - 2021 - Enhancing nonclassical bosonic correlations in a quantum walk network through experimental control of disorder
Laneve, A.; Nosrati, F.; Geraldi, A.; Mahdavipour, K.; Pegoraro, F.; Khazaei Shadfar, M.; Lo Franco, R.; Mataloni, P. - 01a Articolo in rivista
paper: PHYSICAL REVIEW RESEARCH (College Park MD: American Physical Society) pp. - - issn: 2643-1564 - wos: WOS:000695729100006 (4) - scopus: 2-s2.0-85115887109 (5)

11573/1618507 - 2021 - Readout of quantum information spreading using a disordered quantum walk
Nosrati, F.; Laneve, A.; Shadfar, M. K.; Geraldi, A.; Mahdavipour, K.; Pegoraro, F.; Mataloni, P.; Lo Franco, R. - 01a Articolo in rivista
paper: JOURNAL OF THE OPTICAL SOCIETY OF AMERICA. B, OPTICAL PHYSICS (Optical Society of America:2010 Massachusetts Avenue Northwest:Washington, DC 20036:(800)762-6960, (202)223-8130, EMAIL: custserv@osa.org, INTERNET: http://www.osa.org, Fax: (202)223-1096) pp. 2570-2578 - issn: 0740-3224 - wos: WOS:000692200200044 (1) - scopus: 2-s2.0-85114359033 (1)

11573/1339017 - 2019 - Stimulated emission tomography: beyond polarization
Ciampini, M. A.; Geraldi, A.; Cimini, V.; Macchiavello, C.; Sipe, J. E.; Liscidini, M.; Mataloni, P. - 01a Articolo in rivista
paper: OPTICS LETTERS (Optical Society of America:2010 Massachusetts Avenue Northwest:Washington, DC 20036:(800)762-6960, (202)223-8130, EMAIL: custserv@osa.org, INTERNET: http://www.osa.org, Fax: (202)223-1096) pp. 41-44 - issn: 0146-9592 - wos: WOS:000454111300011 (11) - scopus: 2-s2.0-85059244313 (11)

11573/1339020 - 2019 - All-optical implementation of collision-based evolutions of open quantum systems
Cuevas, A.; Geraldi, A.; Liorni, C.; Bonavena, L. D.; De Pasquale, A.; Sciarrino, F.; Giovannetti, V.; Mataloni, P. - 01a Articolo in rivista
paper: SCIENTIFIC REPORTS (London: Springer Nature London: Nature Publishing Group) pp. 3205- - issn: 2045-2322 - wos: WOS:000459983900011 (32) - scopus: 2-s2.0-85062266080 (31)

11573/1474054 - 2019 - Experimental realization of an innovative phase-stable bulk-optic scheme for quantum walks
Geraldi, A.; Bonavena, L. D.; Liorni, C.; Mataloni, P.; Cuevas, A. - 04f Poster
conference: Quantum Information and Measurement, QIM 2019 (ita)
book: Optics InfoBase Conference Papers - (978-1-943580-56-9)

11573/1339013 - 2019 - A novel bulk-optics scheme for quantum walk with high phase stability
Geraldi, Andrea; Bonavena, Luís; Liorni, Carlo; Mataloni, Paolo; Cuevas, Álvaro - 01a Articolo in rivista
paper: CONDENSED MATTER (Basel : MDPI AG, 2016-) pp. - - issn: 2410-3896 - wos: WOS:000464292700002 (3) - scopus: 2-s2.0-85073063091 (3)

11573/1339011 - 2019 - Experimental investigation of superdiffusion via coherent disordered quantum walks
Geraldi, Andrea; Laneve, Alessandro; Bonavena, L. D.; Sansoni, L.; Ferraz, J.; Fratalocchi, A.; Sciarrino, F.; Cuevas, A.; Mataloni, P. - 01a Articolo in rivista
paper: PHYSICAL REVIEW LETTERS (American Institute of Physics:2 Huntington Quadrangle, Suite 1NO1:Melville, NY 11747:(800)344-6902, (631)576-2287, EMAIL: subs@aip.org, INTERNET: http://www.aip.org, Fax: (516)349-9704) pp. 140501- - issn: 0031-9007 - wos: WOS:000488514800003 (25) - scopus: 2-s2.0-85073055778 (26)

11573/1474136 - 2018 - Stimulated emission tomography of hyperentangled states
Ciampini, M. A.; Geraldi, A.; Cimini, V.; Sipe, J. E.; Macchiavello, C.; Liscidini, M.; Mataloni, P. - 04b Atto di convegno in volume
conference: CLEO: QELS_Fundamental Science, CLEO_QELS 2018 (usa)
book: Optics InfoBase Conference Papers - (978-1-943580-42-2)

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