arXiv subjects

Gennaro Zanfardino

Publications and source records attributed to Gennaro Zanfardino.

6 recordsLinked to original sources

arXiv2026

Observation of associative-memory retrieval and spin-glass phases on a photonic quantum simulator

Models of interacting complex systems provide the fundamental statistical physics reference frame for the study and the understanding of associative memories, machine learning, and the dynamics of neural networks. On the other hand, simulating complex multi-synaptic interactions on a classical hardware is computationally demanding due to the super-linear scaling of the system complexity. Photonic quantum technologies provide a promising solution to these limitations by leveraging on their inherent speed and parallel processing ability in order to simulate complex networks. Recently, a connection between multiphoton processes and generalized $p$-body Hopfield models has been theoretically established. Here, we design and demonstrate an experimental platform that exploits single photons distributed across a set of optical modes, in which controlled arrays of binary phase shifters act as Ising-like neurons. We focus specifically on a fully connected Hopfield Hamiltonian with four-body local interaction terms, realized via two-photon processes. Through quantum simulations on programmable photonic processors, the study identifies three distinct regimes: a memory retrieval phase, a spin-glass memory "black-out" phase, and a paramagnetic phase. Experimental results confirm successful memory retrieval at low storage capacities and temperatures, where the system consistently relaxes to fixed points with high memory overlap, effectively reconstructing the stored patterns. Future research will extend the platform design to investigate networks with local or dilute interactions, while advances in the realization of scalable photonic circuits will enable architectures that encompass very large numbers of interacting spins.

quant-ph↗

arXiv2025

Geometric measures of quantum nonlocality: characterization, quantification, and comparison by distances and operations

We introduce a geometric framework for studying Bell nonlocality in Hilbert space, where, for a given quantum state, nonlocality is quantified by the distance between the state and the set of local states. This approach applies to any Bell inequality and any measurement scenario. Whenever the local set is characterized, the proposed nonlocality measure can be computed explicitly. As a general result, we prove that for any scenario in arbitrary dimension the closest local state to a Werner state is itself a Werner state, and analogously, the closest local state to an isotropic state is again isotropic. In the two-qubit case, we further show that the closest local state to a Bell-diagonal state is Bell-diagonal as well. These structural results are independent of the specific Bell inequality considered, thus revealing intrinsic geometric features of these families of states and providing significant simplifications for computing the proposed measures. For the Clauser-Horne-Shimony-Holt (CHSH) inequality in two-qubit systems and the Collins-Gisin-Linden-Massar-Popescu (CGLMP) inequality for two qudits of arbitrary finite dimension, we derive explicit geometric measures of nonlocality for Bell-diagonal, Werner, and isotropic states using various distance metrics, including the trace, Hellinger, Hilbert-Schmidt distances, and relative entropy. Furthermore, we prove in all generality that for all scenarios in which the local set is not fully characterized, the geometric measures provide rigorous lower bounds on nonlocality

quant-ph↗

arXiv2025

Multiphoton quantum simulation of the generalized Hopfield memory model

In the present work, we introduce, develop, and investigate a connection between multiphoton quantum interference, a core element of emerging photonic quantum technologies, and Hopfieldlike Hamiltonians of classical neural networks, the paradigmatic models for associative memory and machine learning in systems of artificial intelligence. Specifically, we show that combining a system composed of Nph indistinguishable photons in superposition over M field modes, a controlled array of M binary phase-shifters, and a linear-optical interferometer, yields output photon statistics described by means of a p-body Hopfield Hamiltonian of M Ising-like neurons +-1, with p = 2Nph. We investigate in detail the generalized 4-body Hopfield model obtained through this procedure and show that it realizes a transition from a memory retrieval to a memory black-out regime, i.e. a spin-glass phase, as the amount of stored memory increases. The mapping enables novel routes to the realization and investigation of disordered and complex classical systems via efficient photonic quantum simulators, as well as the description of aspects of structured photonic systems in terms of classical spin Hamiltonians.

quant-ph↗

arXiv2025

Chiral and flavor oscillations in quantum field theory

Massive fermions produced through weak charged interactions possess a definite chirality, which is not conserved during free propagation, leading to chiral oscillations. Neutrinos also exhibit flavor oscillations. These phenomena have been extensively studied - both individually and within a unified framework - using the first quantization approach, but only separately in the context of quantum field theory. In this work, we address this gap by developing a quantum field theory treatment of flavor-chiral oscillations. Focusing on the case of two-flavor mixing, we compute the expectation values of the (non-conserved) chiral-flavor charges and recover the same oscillation formulas obtained in the first quantization formalism. These charges are diagonalized via Bogoliubov transformations in both the chiral and flavor sectors. Such transformations reveal a non-trivial structure of the chiral-flavor vacuum, which consists of a condensate of particles with definite masses and helicities.

hep-ph↗

arXiv2024

Chiral and flavor oscillations in a hyperentangled neutrino state

In addition to flavor oscillations, Dirac neutrinos also undergo the so-called chiral oscillations, a consequence of the free-particle dynamics under the Dirac equation. Such a transition between different chiralities affect the flavor transitions, but also can generate non-trivial correlations between the internal degrees of freedom of the particle. In this paper, we show that the state of a massive oscillating neutrino produced by weak interaction process, is an hyperentangled state, in which flavor, chirality, and spin exhibit non-trivial correlations. Using complete complementarity relations, we show that both chiral and flavor oscillations redistribute correlations and coherence in time among different partitions of the system. In a similar way, we consider a spin entangled lepton-antineutrino pair and show that there is a dynamical redistribution of spin-spin entanglement into correlations and coherence between the other degrees-of-freedom. Our analysis provides a complete characterization of the quantum correlations involved in lepton-antineutrino pairs and in single particle neutrino evolution, and provides a further insight on possible routes to interpret and measure chiral oscillations.

quant-ph↗

arXiv2024

Chiral oscillations in quantum field theory

Dirac particles have two intrinsic degrees-of-freedom, helicity and chirality. While helicity is conserved in time, chirality is not constant under time evolution for massive particles, yielding the phenomenon of chiral oscillations. So far, chiral oscillations have been mainly described in the framework of single particle relativistic quantum mechanics. In this paper, we present a quantum field theory approach to chiral oscillations in analogy with the one used to describe flavor mixing and oscillations. By taking the expectation value of chiral charges, we obtain the same chiral oscillation formula derived via standard relativistic quantum mechanics. We find that chiral charges are diagonalized by a Bogoliubov transformation: this implies that the vacuum for particles with definite chirality is orthogonal to the one for those with definite energy. In the case of neutrinos, our results can be further extended to include also flavor oscillations.

hep-ph↗