Loïc Henriet

We analyze the topological deformations of the ground state manifold of a quantum spin-1/2 in a magnetic field induced by a coupling to an ohmic quantum dissipative environment at zero temperature. From Bethe ansatz results and a variational approach, we confirm that the Chern number associated with the geometry of the reduced spin ground state manifold is preserved in the delocalized phase. We report a divergence of the Berry curvature at the critical coupling for magnetic fields aligned along… Voir plus

We analyze the topological deformations of the ground state manifold of a quantum spin-1/2 in a magnetic field induced by a coupling to an ohmic quantum dissipative environment at zero temperature. From Bethe ansatz results and a variational approach, we confirm that the Chern number associated with the geometry of the reduced spin ground state manifold is preserved in the delocalized phase. We report a divergence of the Berry curvature at the critical coupling for magnetic fields aligned along the equator. This divergence is caused by the complete quenching of the transverse magnetic field by the bath associated with a gap closing that occurs at the localization Kosterlitz-Thouless quantum phase transition in this model. Recent experiments in quantum circuits have engineered nonequilibrium protocols to access topological properties from a measurement of a dynamical Chern number defined via the out-of-equilibrium spin expectation values. Applying a numerically exact stochastic Schrödinger approach we find that, for a fixed field sweep velocity, the bath induces a crossover from (quasi)adiabatic to nonadiabatic dynamical behavior when the spin bath coupling increases. We further provide an intuitive physical explanation of the bath-induced breakdown of adiabaticity in analogy to the Faraday effect in electromagnetism. We demonstrate that the driving of the spin leads to the production of a large number of bosonic excitations in the bath, which strongly affect the spin dynamics. Finally, we quantify the spin-bath entanglement and formulate an analogy with an effective model at thermal equilibrium. Voir moins

We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons… Voir plus

We review recent developments regarding the quantum dynamics and many-body physics with light, in superconducting circuits and Josephson analogues, by analogy with atomic physics. We start with quantum impurity models addressing dissipative and driven systems. Both theorists and experimentalists are making efforts towards the characterization of these non-equilibrium quantum systems. We show how Josephson junction systems can implement the equivalent of the Kondo effect with microwave photons. The Kondo effect can be characterized by a renormalized light frequency and a peak in the Rayleigh elastic transmission of a photon. We also address the physics of hybrid systems comprising mesoscopic quantum dot devices coupled with an electromagnetic resonator. Then, we discuss extensions to Quantum Electrodynamics (QED) Networks allowing one to engineer the Jaynes–Cummings lattice and Rabi lattice models through the presence of superconducting qubits in the cavities. This opens the door to novel many-body physics with light out of equilibrium, in relation with the Mott–superfluid transition observed with ultra-cold atoms in optical lattices. Then, we summarize recent theoretical predictions for realizing topological phases with light. Synthetic gauge fields and spin–orbit couplings have been successfully implemented in quantum materials and with ultra-cold atoms in optical lattices — using time-dependent Floquet perturbations periodic in time, for example — as well as in photonic lattice systems. Finally, we discuss the Josephson effect related to Bose–Hubbard models in ladder and two-dimensional geometries, producing phase coherence and Meissner currents. The Bose–Hubbard model is related to the Jaynes–Cummings lattice model in the large detuning limit between light and matter (the superconducting qubits). In the presence of synthetic gauge fields, we show that Meissner currents subsist in an insulating Mott phase. Voir moins

Cet ouvrage couvre les programmes de physique quantique de MP et PC, ainsi que le programme de physique statistique de MP. Il s’adresse aux étudiants de classes préparatoires et de licence universitaire, ainsi qu’aux candidats aux concours de l’enseignement.
Chaque chapitre comprend le cours détaillé et ses références, des questions sur le cours et des exercices corrigés, ainsi qu’une analyse de document scientifique corrigée et une ouverture sur un point théorique ou expérimental « pour… Voir plus

Cet ouvrage couvre les programmes de physique quantique de MP et PC, ainsi que le programme de physique statistique de MP. Il s’adresse aux étudiants de classes préparatoires et de licence universitaire, ainsi qu’aux candidats aux concours de l’enseignement.
Chaque chapitre comprend le cours détaillé et ses références, des questions sur le cours et des exercices corrigés, ainsi qu’une analyse de document scientifique corrigée et une ouverture sur un point théorique ou expérimental « pour aller plus loin ».
Ce livre présente les bases historiques et théoriques de la mécanique quantique ondulatoire, de l’effet photoélectrique à l’équation de Schrödinger et ses conséquences.
L’introduction à la physique statistique concerne les systèmes en équilibre thermique avec un thermostat. Partant de la loi de Boltzmann, l’étude porte à la fois sur les systèmes à niveaux d’énergie discrets et continus. Voir moins

We address dissipation effects on the nonequilibrium quantum dynamics of an ensemble of spins-12 coupled via an Ising interaction. Dissipation is modeled by a (Ohmic) bath of harmonic oscillators at zero temperature and correspond either to the sound modes of a one-dimensional Bose-Einstein (quasi-)condensate or to the zero-point fluctuations of a long transmission line. We consider the dimer comprising two spins and the quantum Ising chain with long-range interactions and develop an… Voir plus

We address dissipation effects on the nonequilibrium quantum dynamics of an ensemble of spins-12 coupled via an Ising interaction. Dissipation is modeled by a (Ohmic) bath of harmonic oscillators at zero temperature and correspond either to the sound modes of a one-dimensional Bose-Einstein (quasi-)condensate or to the zero-point fluctuations of a long transmission line. We consider the dimer comprising two spins and the quantum Ising chain with long-range interactions and develop an (mathematically and numerically) exact stochastic approach to address nonequilibrium protocols in the presence of an environment. For the two-spin case, we first investigate the dissipative quantum phase transition induced by the environment through quantum quenches and study the effect of the environment on the synchronization properties. Then we address Landau-Zener-Stueckelberg-Majorana protocols for two spins and for the spin array. In this latter case, we adopt a stochastic mean-field point of view and present a Kibble-Zurek-type argument to account for interaction effects in the lattice. Such dissipative quantum spin arrays can be realized in ultracold atoms, trapped ions, and mesoscopic systems and are related to Kondo lattice models. Voir moins

We theoretically investigate a quantum dot coupled to fermionic (electronic) leads and show how zero-point quantum fluctuations stemming from bosonic environments permit the rectification of the current. The bosonic baths are either external impedances modeled as tunable transmission lines or LC resonators (single-mode cavities). Voltage fluctuations stemming from the external impedances at zero temperature are described through harmonic oscillators (photon-like excitations) producing the… Voir plus

We theoretically investigate a quantum dot coupled to fermionic (electronic) leads and show how zero-point quantum fluctuations stemming from bosonic environments permit the rectification of the current. The bosonic baths are either external impedances modeled as tunable transmission lines or LC resonators (single-mode cavities). Voltage fluctuations stemming from the external impedances at zero temperature are described through harmonic oscillators (photon-like excitations) producing the quantum vacuum fluctuations. The differing sizes of the zero-point fluctuations of the quantum vacuum break the spatial symmetry of the system if the quantum dot is coupled to two reservoirs or two junctions with different bosonic environments. We consider current rectification and power production when the system is operated as a heat engine in both non-resonant and resonant sequential tunneling cases. Voir moins

Spontaneous synchronization between coupled periodic systems occur in a wealth of classical physical setups. Here, we show theoretically that the phase of two distinct quantum harmonic oscillators spontaneously synchronize when they are strongly coupled to a common bosonic quantum dissipative environment at zero temperature, in the absence of any driving mechanism. To do so, we compute the dynamics of the oscillators with an exact master equation obtained from a path integral formalism. Above… Voir plus

Spontaneous synchronization between coupled periodic systems occur in a wealth of classical physical setups. Here, we show theoretically that the phase of two distinct quantum harmonic oscillators spontaneously synchronize when they are strongly coupled to a common bosonic quantum dissipative environment at zero temperature, in the absence of any driving mechanism. To do so, we compute the dynamics of the oscillators with an exact master equation obtained from a path integral formalism. Above some value of the system-environment coupling strength, we observe numerically a strongly reduced damping and a frequency locking in the dynamics of the oscillators. Beyond the synchronization mechanism, we also describe the rich phenomenology of the dynamics in the model and notably identify the additional emergence of a regime with long-lived oscillations. Voir moins

The Rabi model considers a two-level system (or spin-1/2) coupled to a quantized harmonic oscillator and describes the simplest interaction between matter and light. The recent experimental progress in solid-state circuit quantum electrodynamics has engendered theoretical efforts to quantitatively describe the mathematical and physical aspects of the light-matter interaction beyond the rotating wave approximation. We develop a stochastic non-perturbative Schr\"{o}dinger equation approach which… Voir plus

The Rabi model considers a two-level system (or spin-1/2) coupled to a quantized harmonic oscillator and describes the simplest interaction between matter and light. The recent experimental progress in solid-state circuit quantum electrodynamics has engendered theoretical efforts to quantitatively describe the mathematical and physical aspects of the light-matter interaction beyond the rotating wave approximation. We develop a stochastic non-perturbative Schr\"{o}dinger equation approach which enables us to access the strong-coupling limit of the Rabi model and study the effects of dissipation and AC drive in an exact manner. We consider the high-Q cavity limit and include the effect of ohmic noise on the non-Markovian spin dynamics resulting in Kondo-type correlations. We compute the time evolution of spin variables in various conditions. As a scope, we discuss the possibility to reach a steady state with one polariton in realistic experimental conditions. Voir moins