Paolo Facchi

University of Bari Aldo Moro

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Saverio Pascazio

University of Bari Aldo Moro

195

Francesco V. Pepe

Istituto Nazionale di Fisica Nucleare, Sezione di Bari

Kazuya Yuasa

Waseda University

Giuseppe Florio

Polytechnic University of Bari

Daniel Burgarth

Macquarie University

Hiromichi Nakazato

Waseda University

G. Marmo

University of Naples Federico II

Marilena Ligabò

University of Bari Aldo Moro

Davide Lonigro

Friedrich-Alexander-Universität Erlangen-Nürnberg

Antonello Scardicchio

Istituto Nazionale di Fisica Nucleare, Sezione di Trieste

Cooperative Institutions

University of Bari Aldo Moro

Istituto Nazionale di Fisica Nucleare, Sezione di Bari

Istituto Nazionale di Fisica Nucleare

Centre National de la Recherche Scientifique

Istituto Nazionale di Fisica Nucleare, Sezione di Napoli

Sorbonne Université

Waseda University

National Interuniversity Consortium for the Physical Sciences of Matter

University of Naples Federico II

Laboratoire Kastler Brossel

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Condensation of vanishing photon emission rates in random atomic clouds

arXiv (Cornell University) (2024)

Viviana Viggiano Romain Bachelard Fabio Deelan Cunden Paolo Facchi Robin Kaiser

In the collective photon emission from atomic clouds both the atomic transition frequency and the decay rate are modified compared to a single isolated atom, leading to the effects of superradiance and subradiance. In this Letter, we analyse the properties of the Euclidean random matrix associated to the radiative dynamics of a cold atomic cloud, previously investigated in the contexts of photon localization and Dicke super- and subradiance. We present evidence of a new type of phase transition, surprisingly controlled by the cooperativeness parameter, rather than the spatial density or the diagonal disorder. The numerical results corroborate the occurrence of such a phase transition at a critical value of the cooperativeness parameter, above which the lower edge of the spectrum vanishes exhibiting a macroscopic accumulation of eigenvalues. Independent evaluations based on the two phenomena provide the same value of the critical cooperativeness parameter.

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Robustness of optimal working points for nonadiabatic holonomic quantum computation

Laser Physics (2006)

A. Trullo Paolo Facchi Rosario Fazio Giuseppe Florio Vittorio Giovannetti

Geometric phases are an interesting resource for quantum computation, also in view of their robustness against decoherence effects. We study here the effects of the environment on a class of one-qubit holonomic gates that have been recently shown to be characterized by "optimal" working times. We numerically analyze the behavior of these optimal points and focus on their robustness against noise.

Robustness

Holonomic

10.1134/s1054660x06100094

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On the assumption of initial factorization in the master equation for weakly coupled systems I: General framework

Annals of Physics (2006)

S. Tasaki Kazuya Yuasa Paolo Facchi Gen Kimura Hiromichi Nakazato

10.1016/j.aop.2006.06.004

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Citations (23)

Maximally multipartite entangled states

arXiv (Cornell University) (2007)

Paolo Facchi Giuseppe Florio Giorgio Parisi Saverio Pascazio

We introduce the notion of maximally multipartite entangled states of n qubits as a generalization of the bipartite case. These pure states have a bipartite entanglement that does not depend on the bipartition and is maximal for all possible bipartitions. They are solutions of a minimization problem. Examples for small n are investigated, both analytically and numerically.

Multipartite

Multipartite entanglement

10.48550/arxiv.0710.2868

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CONTROL OF DECOHERENCE VIA QUANTUM ZENO SUBSPACES

International Journal of Modern Physics B (2006)

Paolo Facchi Hiromichi Nakazato Saverio Pascazio Shuichi Tasaki

We discuss three control strategies, whose objective is to counter the effects of decoherence: the first strategy hinges upon the quantum Zeno effect, the second makes use of frequent unitary interruptions ("bang-bang" pulses), and the third of a strong, continuous coupling. Decoherence can be suppressed only if the frequency τ -1 of the measurements/pulses is large enough or if the coupling K is sufficiently strong. Otherwise, if τ -1 or K are large, but not sufficiently large, all these control procedures accelerate decoherence.

Quantum Zeno effect

Decoherence-free subspaces

10.1142/s0217979206034017

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Report on 1904.03627v4

arXiv (Cornell University) (2021)

Daniel Burgarth Paolo Facchi Martin Fraas Robin Hillier

Dynamical decoupling is the leading technique to remove unwanted interactions in a vast range of quantum systems through fast rotations.But what determines the time-scale of such rotations in order to achieve good decoupling?By providing an explicit counterexample of a qubit coupled to a charged particle and magnetic monopole, we show that such time-scales cannot be decided by the decay profile induced by the noise: even though the system shows a quadratic decay (a Zeno region revealing non-Markovian noise), it cannot be decoupled, no matter how fast the rotations.

10.21468/scipost.report.3127

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Boundaries without boundaries

Annals of Physics (2018)

Paolo Facchi Giancarlo Garnero G. Marmo Joseph Samuel Supurna Sinha

Hamiltonian (control theory)

Free particle

10.1016/j.aop.2018.04.030

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Citations (14)

Van Hove's “λ2t” limit in nonrelativistic and relativistic field-theoretical models

Chaos Solitons & Fractals (2001)

Paolo Facchi Saverio Pascazio

Limiting

10.1016/s0960-0779(01)00090-x

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Experimental Investigation of Quantum Decay via Integrated Photonics

Andrea Crespi Francesco V. Pepe Paolo Facchi Fabio Sciarrino Paolo Mataloni

Whereas classical physics generally predicts an exponential trend for the temporal decay of an unstable state, quantum mechanics provides a rather different description. The decay is initially quadratic, while at very large times it follows a power-law. Actually, the latter regime has never been observed experimentally. Here we employ arrays of femtosecond-laser-written optical waveguides to optically realize quantum systems where a discrete state is coupled to and can decay into a continuum. The transverse optical modes represent distinct quantum states of the photon and the temporal evolution of the system is mapped into the longitudinal propagation coordinate. By injecting laser light in the fabricated structures, and by imaging with high dynamic range the scattered light from above, we are able to observe experimentally different decay regimes, including the power-law tail. This process can be viewed as the quantum simulation of a quantum decay phenomenon.

Exponential decay

Quantum imaging

Quantum system

10.3390/proceedings2019012009

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Spin Glass Model of Operational Risk

arXiv (Cornell University) (2010)

Marco Bardoscia Paolo Facchi Saverio Pascazio A. Trullo

We analyze operational risk in terms of a spin glass model. Several regimes are investigated, as a functions of the parameters that characterize the dynamics. The system is found to be robust against variations of these parameters. We unveil the presence of limit cycles and scrutinize the features of the asymptotic state.

Dynamics

10.48550/arxiv.1002.3560

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