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L’invenzione matematica e scientifica, al di là dei miti tecnoscientifici.: Prefazione
No full textG. Longo. L’invenzione matematica e scientifica, al di là dei miti tecnoscientifici. Prefazione a: "Il Liceo matematico: un approccio storico e interdisciplinare all’insegnamento delle scienze e della matematica" di A. Nigrelli e F. S. Tortoriello (Mimesis, di prossima pubblicazione, 2025): (LongoPrefazione-libroSalerno.pdf); An extended and largely revised summary in English, to appear in Systems, 2025: (systemic-unity.pdf)International audienc
Pascal intempestif, actes du colloque du Collège de France d'octobre 2023
No full textInternational audienc
Turning qubit noise into an advantage: Automatic state preparation and long-time dynamics for impurity models on quantum computers
No full text17 pages, 6 figuresInternational audienceNoise is often regarded as a limitation of quantum computers. In this work, we show that in the dynamical mean-field theory (DMFT) approach to strongly correlated systems, it can actually be harnessed to our advantage. Indeed, DMFT maps a lattice model onto an impurity model, namely, a finite system coupled to a dissipative bath. While standard approaches require a large number of high-quality qubits in a unitary context, we propose a circuit that harvests amplitude damping to reproduce the dynamics of this model with a blend of noisy and noiseless qubits. We find compelling advantages with this approach: a substantial reduction in the number of qubits, the ability to reach longer time dynamics, and no need for ground-state search and preparation. This method would naturally fit in a partial quantum error correction framework
Quantum machine learning via continuous-variable cluster states and teleportation
No full textInternational audienceA new approach suitable for distributed quantum machine learning and exhibiting memory is proposed for a photonic platform. This measurement-based quantum reservoir computing takes advantage of continuous variable cluster states as the main quantum resource. Cluster states are key to several photonic quantum technologies, enabling universal quantum computing as well as quantum communication protocols. The proposed measurement-based quantum reservoir computing is based on a neural network of cluster states and local operations, where input data are encoded through measurement, thanks to quantum teleportation. In this design, measurements enable input injections, information processing and continuous monitoring for time series processing. The architecture's power and versatility are tested by performing a set of benchmark tasks showing that the protocol displays internal memory and is suitable for both static and temporal information processing without hardware modifications. This design opens the way to distributed machine learning
Par-delà les belles-lettres: nouveaux horizons pour une histoire littéraire du Japon au 19e siècle
No full textHierarchical Verification of Non-Gaussian Coherence in Bosonic Quantum States
No full textInternational audienceNon-Gaussianity, a distinctive characteristic of bosonic quantum states, is pivotal in advancing quantum networks, fault-tolerant quantum computing, and high-precision metrology. Verifying the quantum nature of a state, particularly its non-Gaussian features, is essential for ensuring the reliability and performance of these technologies. However, the specific properties required for each application demand tailored validation thresholds. Here, we introduce a hierarchical framework comprising absolute, relative, and qubit-specific thresholds to assess the non-Gaussianity of local coherences. We illustrate this framework using heralded optical non-Gaussian states with the highest purities available in optical platforms. This comprehensive framework presents the first detailed evaluation of number state coherences and can be extended to a wide range of bosonic states
Optimal control for preparing fractional quantum Hall states in optical lattices
No full textInternational audiencePreparing fractional quantum Hall (FQH) states represents a key challenge for quantum simulators. While small Laughlin-type states have been realized by manipulating two atoms or two photons, scaling up these settings to larger ensembles stands as an impractical task using existing methods and protocols. In this work, we propose to use optimal-control methods to substantially accelerate the preparation of small Laughlin-type states, and demonstrate that the resulting protocols are also well suited to realize larger FQH states under realistic preparation times. Our schemes are specifically built on the recent optical-lattice experiment [Leonard et al., Nature (2023)], and consist in optimizing very few control parameters: the tunneling amplitudes and linear gradients along the two directions of the lattice. We demonstrate the robustness of our optimal-control schemes against control errors and disorder, and discuss their advantages over existing preparation methods. Our work paves the way to the efficient realization of strongly-correlated topological states in quantum-engineered systems
Enhanced Strange Metallicity due to Hubbard-<math display="inline"><mi>U</mi></math> Coulomb Repulsion
No full textInternational audienceWe solve a model of electrons with Hubbard-U Coulomb repulsion and a random Yukawa coupling to a two-dimensional bosonic bath, using an extended dynamical mean field theory scheme. Our model exhibits a quantum critical point, at which the repulsive component of the electron interactions strongly enhances the effects of the quantum critical bosonic fluctuations on the electrons, leading to a breakdown of Fermi liquid physics and the formation of a strange metal with “Planckian” [O(kBT/ℏ)] quasiparticle decay rates at low temperatures T→0. Furthermore, the eventual Mott transition that occurs as the repulsion is increased seemingly bounds the maximum decay rate in the strange metal. Our results provide insight into low-temperature strange metallicity observed in proximity to a Mott transition, as is observed, for instance, in recent experiments on certain moiré materials
Dynamic Realization of Majorana Zero Modes in a Particle-Conserving Ladder
No full textInternational audienceWe present a scheme to realize a topological superconducting system supporting Majorana zero modes, within a number-conserving framework suitable for optical-lattice experiments. Our approach builds on the engineering of pair-hopping processes on a ladder geometry, using a sequence of pulses that activate single-particle hopping in a time-periodic manner. We demonstrate that this dynamic setting is well captured by an effective Hamiltonian that preserves the parity symmetry, a key requirement for the stabilization of Majorana zero modes. The phase diagram of our system is determined using a bosonization theory, which is then validated by a numerical study of the topological bulk gap and entanglement spectrum using matrix product states. Our results indicate that Majorana zero modes can be stabilized in a large parameter space, accessible in optical-lattice experiments
Universal Waterfall Feature in Cuprate Superconductors: Evidence of a Momentum-Driven Crossover
No full textInternational audienceWe study two related universal anomalies of the spectral function of cuprates, so called waterfall and high-energy kink features, by a combined cellular dynamical mean-field theory and angle-resolved photoemission study for the oxychloride NaCaCuOCl (Na-CCOC). Tracing their origin back to an interplay of spin-polaron and local correlation effects both in undoped and hole-doped (Na-)CCOC, we establish them as a universal crossover between regions differing in the momentum dependence of the coupling and not necessarily in the related quasiparticles' energies. The proposed scenario extends to doping levels coinciding with the cuprate's superconducting dome and motivates further investigations of the fate of spin-polarons in the superconducting phase