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Non-Stabilizerness of Sachdev-Ye-Kitaev Model
No full textInternational audienceWe study the non-stabilizerness or quantum magic of the Sachdev-Ye-Kitaev () model, a prototype example of maximally chaotic quantum matter. We show that the Majorana spectrum of its ground state, encoding the spreading of the state in the Majorana basis, displays a Gaussian distribution as expected for chaotic quantum many-body systems. We compare our results with the case of the model, describing non-chaotic random free fermions, and show that the Majorana spectrum is qualitatively different in the two cases, featuring an exponential Laplace distribution for the model rather than a Gaussian. From the spectrum we extract the stabilizer Renyi Entropy (SRE) and show that for both models it displays a linear scaling with system size, with a prefactor that is larger for the SYK model, which has therefore higher magic. Finally, we discuss the spreading of quantun magic under unitary dynamics, as described by the evolution of the Majorana spectrum and the stabilizer Renyi Entropy starting from a stabilizer state. We show that the SRE for the model equilibrates rapidly, but that in the steady-state the interacting chaotic SYK model has more magic than the simple . Our results therefore suggest that non-stabilizerness allows to sharply detect many-body quantum chaos
Neural Projected Quantum Dynamics: a systematic study
No full textInternational audienceWe address the challenge of simulating unitary quantum dynamics in large systems using Neural Quantum States, focusing on overcoming the computational instabilities and high cost of existing methods. This work offers a comprehensive formalization of the projected time-dependent Variational Monte Carlo (p-tVMC) method by thoroughly analyzing its two essential components: stochastic infidelity minimization and discretization of the unitary evolution. We investigate neural infidelity minimization using natural gradient descent strategies, identifying the most stable stochastic estimators and introducing adaptive regularization strategies that eliminate the need for manual adjustment of the hyperparameter along the dynamics. We formalize the specific requirements that p-tVMC imposes on discretization schemes for them to be efficient, and introduce four high-order integration schemes combining Taylor expansions, Padé approximants, and Trotter splitting to enhance accuracy and scalability. We benchmark our adaptive methods against a 2D Ising quench, matching state of the art techniques without manual tuning of hyperparameters. This work establishes p-tVMC as a highly promising framework for addressing complex quantum dynamics, offering a compelling alternative for researchers looking to push the boundaries of quantum simulations
Chiral polaron formation on the edge of topological quantum matter
No full textInternational audienceImmersing a mobile impurity in a quantum many-body environment can reveal fundamental properties of the background medium, hence providing a powerful probe of quantum matter. This approach is particularly intriguing when considering media with exotic properties, such as strongly-correlated phases and topological states of matter. In this work, we study the dressing of a mobile impurity interacting with a chiral mode, as provided by the edge of topological quantum matter. The resulting ''chiral polaron'' is characterized by an asymmetric spectral function, which reflects the chirality and group velocity of the topological edge mode and the drag experienced by the mobile impurity. We first build our theoretical understanding from an effective one-dimensional chiral model, which captures the hallmark signatures of the chiral polaron. We then demonstrate how this simple picture extends to realistic models of integer and fractional Chern insulator states, by adapting tensor-network methods to polaron spectroscopy. Injecting mobile impurities on the edge of topological quantum matter is shown to be a powerful tool to probe exotic edge properties, particularly suitable for cold-atom experiments
Sur la piste du clair-obscur: frontières et nocturnité
No full textInternational audienceIntroduction du volum
L'amministrazione militare e civile dell'Italia meridionale bizantina (sec. VI-IX)
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Acting <i>on</i> and <i>with</i> animals: A ‘turn’ that doesn’t start from nothing
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Conclusions: The Settlement History of Kiriath-Jearim
No full textInternational audienceThis volume reports the results of the Tel Aviv University and the Collège de France’s excavations at Kiriath-jearim. The site, located on a strategic peak west of Jerusalem, is of crucial importance for the study of the archaeology and history of Iron Age Israel and Judah, and later, of Hellenistic and Roman Judea. Specific attention is given to the later phases of the Iron Age, attempting to shed light on the biblical tradition that the site accommodated the temple of the Ark
