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Dalibard J.,Kastler-Brossel Laboratory | Gerbier F.,Kastler-Brossel Laboratory | Juzeliunas G.,Vilnius University | Ohberg P.,Heriot - Watt University
Reviews of Modern Physics | Year: 2011

When a neutral atom moves in a properly designed laser field, its center-of-mass motion may mimic the dynamics of a charged particle in a magnetic field, with the emergence of a Lorentz-like force. In this Colloquium the physical principles at the basis of this artificial (synthetic) magnetism are presented. The corresponding Aharonov-Bohm phase is related to the Berry's phase that emerges when the atom adiabatically follows one of the dressed states of the atom-laser interaction. Some manifestations of artificial magnetism for a cold quantum gas, in particular, in terms of vortex nucleation are discussed. The analysis is then generalized to the simulation of non-Abelian gauge potentials and some striking consequences are presented, such as the emergence of an effective spin-orbit coupling. Both the cases of bulk gases and discrete systems, where atoms are trapped in an optical lattice, are addressed. © 2011 American Physical Society.

Bloch I.,Ludwig Maximilians University of Munich | Bloch I.,Max Planck Institute of Quantum Optics | Dalibard J.,Kastler-Brossel Laboratory | Nascimbene S.,Ludwig Maximilians University of Munich | Nascimbene S.,Kastler-Brossel Laboratory
Nature Physics | Year: 2012

Ultracold quantum gases offer a unique setting for quantum simulation of interacting many-body systems. The high degree of controllability, the novel detection possibilities and the extreme physical parameter regimes that can be reached in these 'artificial solids' provide an exciting complementary set-up compared with natural condensed-matter systems, much in the spirit of Feynman's vision of a quantum simulator. Here we review recent advances in technology and discuss progress in a number of areas where experimental results have already been obtained. © 2012 Macmillan Publishers Limited. All rights reserved.

Nascimbene S.,Kastler-Brossel Laboratory
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2013

We propose an experimental implementation of a topological superfluid with ultracold fermionic atoms. An optical superlattice is used to juxtapose a 1D gas of fermionic atoms and a 2D conventional superfluid of condensed Feshbach molecules. The latter acts as a Cooper pair reservoir and effectively induces a superfluid gap in the 1D system. Combined with a spin-dependent optical lattice along the 1D tube and laser-induced atom tunnelling, we obtain a topological superfluid phase. In the regime of weak couplings to the molecular field and for a uniform gas, the atomic system is equivalent to Kitaev's model of a p-wave superfluid. Using a numerical calculation, we show that the topological superfluidity is robust beyond the perturbative limit and in the presence of a harmonic trap. Finally, we describe how to investigate some physical properties of the Majorana fermions located at the topological superfluid boundaries. In particular, we discuss how to prepare and detect a given Majorana edge state. © 2013 IOP Publishing Ltd.

Haroche S.,Kastler-Brossel Laboratory | Haroche S.,Collège de France
Reviews of Modern Physics | Year: 2013

Microwave photons trapped in a superconducting cavity constitute an ideal system to realize some of the thought experiments imagined by the founding fathers of quantum physics. The interaction of these trapped photons with Rydberg atoms crossing the cavity illustrates fundamental aspects of measurement theory. The experiments performed with this "photon box" at Ecole Normale Supérieure (ENS) belong to the domain of quantum optics called "cavity quantum electrodynamics." We have realized the nondestructive counting of photons, the recording of field quantum jumps, the preparation and reconstruction of "Schrödinger cat" states of radiation and the study of their decoherence, which provides a striking illustration of the transition from the quantum to the classical world. These experiments have also led to the demonstration of basic steps in quantum information processing, including the deterministic entanglement of atoms and the realization of quantum gates using atoms and photons as quantum bits. This lecture starts by an introduction stressing the connection between the ENS photon box and the ion-trap experiments of David Wineland, whose accompanying lecture recalls his own contribution to the field of single particle control. I give then a personal account of the early days of cavity quantum electrodynamics before describing the main experiments performed at ENS during the last 20 years and concluding by a discussion comparing our work to other researches dealing with the control of single quantum particles. © 2013 Nobel Foundation.

Cooper N.R.,Tcm Group | Dalibard J.,Kastler-Brossel Laboratory | Dalibard J.,Collège de France
Physical Review Letters | Year: 2013

We present a robust scheme by which fractional quantum Hall states of bosons can be achieved for ultracold atomic gases. We describe a new form of optical flux lattice, suitable for commonly used atomic species with ground state angular momentum Jg=1, for which the lowest energy band is topological and nearly dispersionless. Through exact diagonalization studies, we show that, even for moderate interactions, the many-body ground states consist of bosonic fractional quantum Hall states, including the Laughlin state and the Moore-Read (Pfaffian) state. These phases are shown to have energy gaps that are larger than temperature scales achievable in ultracold gases. © 2013 American Physical Society.

Delande D.,Kastler-Brossel Laboratory | Orso G.,University Paris Diderot
Physical Review Letters | Year: 2014

Using the transfer-matrix method, we numerically compute the precise position of the mobility edge of atoms exposed to a laser speckle potential and study its dependence versus the disorder strength and correlation function. Our results deviate significantly from previous theoretical estimates using an approximate, self-consistent approach of localization. In particular, we find that the position of the mobility edge in blue-detuned speckles is much lower than in the red-detuned counterpart, pointing out the crucial role played by the asymmetric on-site distribution of speckle patterns. © 2014 American Physical Society.

Delande D.,Kastler-Brossel Laboratory | Sacha K.,Jagiellonian University
Physical Review Letters | Year: 2014

The Gross-Pitaevskii equation - which describes interacting bosons in the mean-field approximation - possesses solitonic solutions in dimension one. For repulsively interacting particles, the stationary soliton is dark, i.e., is represented by a local density minimum. Many-body effects may lead to filling of the dark soliton. Using quasiexact many-body simulations, we show that, in single realizations, the soliton appears totally dark although the single particle density tends to be uniform. © 2014 American Physical Society.

Goldman N.,Collège de France | Goldman N.,Kastler-Brossel Laboratory | Dalibard J.,Collège de France | Dalibard J.,Kastler-Brossel Laboratory
Physical Review X | Year: 2014

Driving a quantum system periodically in time can profoundly alter its long-time dynamics and trigger topological order. Such schemes are particularly promising for generating nontrivial energy bands and gauge structures in quantum-matter systems. Here, we develop a general formalism that captures the essential features ruling the dynamics: the effective Hamiltonian, but also the effects related to the initial phase of the modulation and the micromotion. This framework allows for the identification of driving schemes, based on general N-step modulations, which lead to configurations relevant for quantum simulation. In particular, we explore methods to generate synthetic spin-orbit couplings and magnetic fields in cold-atom setups.

Gerbier F.,Kastler-Brossel Laboratory | Dalibard J.,Kastler-Brossel Laboratory
New Journal of Physics | Year: 2010

We present a scheme that produces a strong U(1)-like gauge field on cold atoms confined in a two-dimensional square optical lattice. Our proposal relies on two essential features, a long-lived metastable excited state that exists for alkaline-earth or ytterbium atoms and an optical superlattice. As in the proposal by Jaksch and Zoller (2003 New J. Phys. 5 56), laser-assisted tunneling between adjacent sites creates an effective magnetic field. In the tight-binding approximation, atomic motion is described by the Harper Hamiltonian, with a flux across each lattice plaquette that can realistically take any value between 0 and π. We show how one can take advantage of the superlattice to ensure that each plaquette acquires the same phase, thus simulating a uniform magnetic field. We discuss the observable consequences of the artificial gauge field on non-interacting bosonic and fermionic gases. We also outline how the scheme can be generalized to non-Abelian gauge fields. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Chevy F.,Kastler-Brossel Laboratory
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2015

In this article, we calculate the friction between two counterflowing bosonic and fermionic superfluids. In the limit where the boson-boson and boson-fermion interactions can be treated within the mean-field approximation, we show that the force can be related to the dynamical structure factor of the fermionic component. Finally, we provide asymptotic expressions for weakly and strongly attractive fermions and show that the damping rate obeys simple scaling laws close to the critical velocity. © 2015 American Physical Society.

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