Aristide Lemaître

Bio: Aristide Lemaître is an academic researcher from Université Paris-Saclay. The author has contributed to research in topics: Quantum dot & Photon. The author has an hindex of 75, co-authored 712 publications receiving 22029 citations. Previous affiliations of Aristide Lemaître include École Normale Supérieure & University of Paris-Sud.

Near-optimal single-photon sources in the solid state

Abstract: A single photon with near-unity indistinguishability is generated from quantum dots in electrically controlled cavity structures. The cavity allows for efficient photon collection while application of an electrical bias cancels charge noise effects.

Lasing in topological edge states of a one-dimensional lattice

Abstract: Topology describes properties that remain unaffected by smooth distortions. Its main hallmark is the emergence of edge states localized at the boundary between regions characterized by distinct topological invariants. Because their properties are inherited from the topology of the bulk, these edge states present a strong immunity to distortions of the underlying architecture. This feature offers new opportunities for robust trapping of light in nano- and micrometre-scale systems subject to fabrication imperfections and environmentally induced deformations. Here, we report lasing in such topological edge states of a one-dimensional lattice of polariton micropillars that implements an orbital version of the Su–Schrieffer–Heeger Hamiltonian. We further demonstrate that lasing in these states persists under local deformations of the lattice. These results open the way to the implementation of chiral lasers in systems with broken time-reversal symmetry and, when combined with polariton interactions, to the study of nonlinear phenomena in topological photonics. Topologically protected lasing is reported in a lattice of polariton micropillars.

Exciton-photon strong-coupling regime for a single quantum dot embedded in a microcavity.

Abstract: We report on the observation of the strong-coupling regime between the excitonic transition of a single GaAs quantum dot and a discrete optical mode of a microdisk microcavity. Photoluminescence is performed at various temperatures to tune the quantum dot exciton with respect to the optical mode. At resonance, we observe a clear anticrossing behavior, signature of the strong-coupling regime. The vacuum Rabi splitting amounts to 400 microeV and is twice as large as the individual linewidths.

Ultrabright source of entangled photon pairs

Abstract: Entangled photon pairs are essential components for practical quantum information applications. Two different approaches for producing entanglement are available: parametric conversion in a nonlinear optical medium, or radiative decay of electron–hole pairs trapped in a semiconductor quantum dot. The first approach has a low intrinsic efficiency; the second suffers from poor collection efficiency. In general, collection of emitted photons from quantum dots is often improved by coupling them to an optical cavity, but this is not straightforward to implement for entangled photon pairs. Dousse et al. have now constructed a suitable optical cavity in the form of a 'photonic molecule' — two connecting identical microcavities that are deterministically coupled to the optically active modes of a pre-selected quantum dot. They show that entangled photon pairs are emitted into two cavity modes, with a rate of 0.12 per excitation pulse. The authors believe that improvements in the fabrication of the device should enable triggered sources of entangled photon pairs, with an overall (creation and collection) efficiency of 80%. Quantum information science requires a source of entangled photon pairs, but existing sources suffer from a low intrinsic efficiency or poor extraction efficiency. Collecting emitted photons from quantum dots can be improved by coupling the dots to an optical cavity, but this is not easy for entangled photon pairs. Now, a suitable optical cavity has been made in the form of a 'photonic' molecule — two identical, connecting microcavities that are deterministically coupled to the optically active modes of a pre-selected quantum dot. A source of triggered entangled photon pairs is a key component in quantum information science1; it is needed to implement functions such as linear quantum computation2, entanglement swapping3 and quantum teleportation4. Generation of polarization entangled photon pairs can be obtained through parametric conversion in nonlinear optical media5,6,7 or by making use of the radiative decay of two electron–hole pairs trapped in a semiconductor quantum dot8,9,10,11. Today, these sources operate at a very low rate, below 0.01 photon pairs per excitation pulse, which strongly limits their applications. For systems based on parametric conversion, this low rate is intrinsically due to the Poissonian statistics of the source12. Conversely, a quantum dot can emit a single pair of entangled photons with a probability near unity but suffers from a naturally very low extraction efficiency. Here we show that this drawback can be overcome by coupling an optical cavity in the form of a ‘photonic molecule’13 to a single quantum dot. Two coupled identical pillars—the photonic molecule—were etched in a semiconductor planar microcavity, using an optical lithography method14 that ensures a deterministic coupling to the biexciton and exciton energy states of a pre-selected quantum dot. The Purcell effect ensures that most entangled photon pairs are emitted into two cavity modes, while improving the indistinguishability of the two optical recombination paths15,16. A polarization entangled photon pair rate of 0.12 per excitation pulse (with a concurrence of 0.34) is collected in the first lens. Our results open the way towards the fabrication of solid state triggered sources of entangled photon pairs, with an overall (creation and collection) efficiency of 80%.

Collective fluid dynamics of a polariton condensate in a semiconductor microcavity

Abstract: Semiconductor microcavities offer unique systems in which to investigate the physics of weakly interacting bosons. Their elementary excitations, polaritons-mixtures of excitons and photons-can accumulate in macroscopically degenerate states to form various types of condensate in a wide range of experimental configurations, under either incoherent or coherent excitation. Condensates of polaritons have been put forward as candidates for superfluidity, and the formation of vortices as well as elementary excitations with linear dispersion are actively sought as evidence to support this. Here, using a coherent excitation triggered by a short optical pulse, we have created and set in motion a macroscopically degenerate state of polaritons that can be made to collide with a variety of defects present in the microcavity. Our experiments show striking manifestations of a coherent light-matter packet, travelling at high speed (of the order of one per cent of the speed of light) and displaying collective dynamics consistent with superfluidity, although one of a highly unusual character as it involves an out-of-equilibrium dissipative system. Our main results are the observation of a linear polariton dispersion accompanied by diffusionless motion; flow without resistance when crossing an obstacle; suppression of Rayleigh scattering; and splitting into two fluids when the size of the obstacle is comparable to the size of the wave packet. This work opens the way to the investigation of new phenomenology of out-of-equilibrium condensates.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Phd by thesis

Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Cavity Optomechanics

Abstract: We review the field of cavity optomechanics, which explores the interaction between electromagnetic radiation and nano- or micromechanical motion This review covers the basics of optical cavities and mechanical resonators, their mutual optomechanical interaction mediated by the radiation pressure force, the large variety of experimental systems which exhibit this interaction, optical measurements of mechanical motion, dynamical backaction amplification and cooling, nonlinear dynamics, multimode optomechanics, and proposals for future cavity quantum optomechanics experiments In addition, we describe the perspectives for fundamental quantum physics and for possible applications of optomechanical devices

Bose-Einstein condensation in a gas of sodium atoms

Abstract: Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.