arXiv subjects

E. Brion

Publications and source records attributed to E. Brion.

At least 19 recordsLinked to original sources

arXiv2025

Collective emission of atomic nanorings around an optical nanofiber

We theoretically investigate the collective emission of one and two circular arrays of two-level atoms surrounding an optical nanofiber. We show that the radiation eigenmodes of a single ring selectively couple to specific guided modes of the fiber, according to their symmetry, and study how the physical parameters of the system control their nature. In particular, we identify situations in which the emission toward radiation modes is highly suppressed with respect to fiber-guided modes while the lifetime of the atomic excitation is enhanced. We further address the case of two identical nanorings positioned at a distance from each other along the nanofiber. By contrast to free-space configurations, the rings can exchange excitations even at large separation through nanofiber guided modes resulting in enhanced sub- and super-radiance with respect to the single-ring case. Our findings suggest that the ring configuration is promising for the implementation of efficient and versatile light-matter nanofiber-based interfaces and the achievement of waveguide quantum electrodynamics.

quant-ph↗

arXiv2024

Phase control of transmission and reflection in a sample of duplicated two-level systems driven by a stationary control field

In this article, we study the optical response of a duplicated two-level atomic medium subjected to a stationary control field and a weak co-propagating probe field, orthogonally polarized to each other. We show that both the reflected and transmitted components of the probe can be absorbed or amplified. Furthermore, for moderate optical depths, the reflection and transmission factors are controlled by the relative phase between the control and probe fields, making the configuration we present here promising for the development of optical devices. We also determine the exact conditions under which reflection and transmission factors can be controlled by the relative phase between the control and probe fields.

quant-ph↗

arXiv2023

Nanofibre-based trap for Rb$_2$ molecule

We describe a theoretical proposal of a nanofibre-based trap for a Rb$_2$ molecule prepared in the metastable state $(1)^3\Sigma^+_u$. The trapping potential results from the combination of a travelling and a standing-wave fields, both carried by the fundamental guided mode HE$_{11}$ of the fibre. We show that, with an experimentally realistic choice of laser frequencies and powers, one can implement a $\approx 200$ $\mu$K-deep well at $\approx 140$ nm from the fibre surface accomodating for $\approx 500$ translational molecular states.

quant-ph↗

arXiv2022

Birefringence and dichroism effects in the spin noise spectra of a spin-1 system

We perform spin noise spectroscopy experiments in metastable helium atoms at room temperature, with a probe light whose frequency is blue detuned from the D0 line. Both circular birefringence fluctuations (Faraday noise) and linear birefringence fluctuations (ellipticity noise) are explored theoretically and experimentally. In particular, it is shown that in both cases but for different optical detunings, two noise resonances are isolated at the Larmor frequency and at twice the Larmor frequency with a behaviour, which strongly depends on the orientation of the probe field polarization. The simple structure of metastable helium allows us to probe, model and explain the changes in the behavior of these peaks in terms of circular and linear dichroisms and birefringences as well as in terms of spin oscillation modes.

quant-ph↗

arXiv2022

Interaction of two Rydberg atoms in the vicinity of an optical nanofibre

We consider two rubidium atoms, prepared in the same S or P Rydberg states near an optical nanofibre. We determine the van der Waals interaction between them and identify novel features, including the reshaping of the interaction anisotropy and the formation of an interaction potential well near the nanofibre for P states. We attribute these phenomena to the breaking of the rotation symmetry around the interatomic axis due to the presence of the fibre. Our work constitutes an important step in the assessment of Rydberg atom-nanofibre quantum interfaces and devices.

quant-ph↗

arXiv2020

Spontaneous emission and energy shifts of a Rydberg rubidium atom close to an optical nanofiber

In this paper, we report on numerical calculations of the spontaneous emission rates and Lamb shifts of a $^{87}\text{Rb}$ atom in a Rydberg-excited state $\left(n\leq30\right)$ located close to a silica optical nanofiber. We investigate how these quantities depend on the fiber's radius, the distance of the atom to the fiber, the direction of the atomic angular momentum polarization as well as the different atomic quantum numbers. We also study the contribution of quadrupolar transitions, which may be substantial for highly polarizable Rydberg states. Our calculations are performed in the macroscopic quantum electrodynamics formalism, based on the dyadic Green's function method. This allows us to take dispersive and absorptive characteristics of silica into account; this is of major importance since Rydberg atoms emit along many different transitions whose frequencies cover a wide range of the electromagnetic spectrum. Our work is an important initial step towards building a Rydberg atom-nanofiber interface for quantum optics and quantum information purposes.

quant-ph↗

arXiv2018

Spontaneous emission of a sodium Rydberg atom close to an optical nanofibre

We report on numerical calculations of the spontaneous emission rate of a Rydberg-excited sodium atom in the vicinity of an optical nanofibre. In particular, we study how this rate varies with the distance of the atom to the fibre, the fibre's radius, the symmetry s or p of the Rydberg state as well as its principal quantum number. We find that a fraction of the spontaneously emitted light can be captured and guided along the fibre. This suggests that such a setup could be used for networking atomic ensembles, manipulated in a collective way due to the Rydberg blockade phenomenon.

quant-ph↗

arXiv2018

Diagrammatic treatment of few-photon scattering from a Rydberg blockaded atomic ensemble in a cavity

In a previous letter we studied the giant optical nonlinearities of a Rydberg atomic medium within an optical cavity, in the Schwinger-Keldysh formalism. In particular, we calculated the non-linear contributions to the spectrum of the light transmitted through the cavity. In this article we spell out the essential details of this calculation, and we show how it can be extended to higher input photon numbers, and higher order correlation functions. As a relevant example, we calculate and discuss the three-photon correlation function of the transmitted light, and discuss its physical significance in terms of the polariton energy levels of the Rydberg medium within the optical cavity.

quant-ph↗

arXiv2017

Coherent Population Oscillation-Based Light Storage

We theoretically study the propagation and storage of a classical field in a $Λ$-type atomic medium using coherent population oscillations (CPOs). We show that the propagation eigenmodes strongly relate to the different CPO modes of the system. Light storage in such modes is discussed by introducing a "populariton" quantity, a mixture of populations and field, by analogy to the dark state polariton used in the context of electromagnetically induced transparency light storage protocol. As experimentally shown, this memory relies on populations and is then - by contrast with usual Raman coherence optical storage protocols - robust to dephasing effects.

quant-ph↗

arXiv2016

Inelastic photon scattering via the intracavity Rydberg blockade

Electromagnetically induced transparency (EIT) in a ladder system involving a Rydberg level is known to yield giant optical nonlinearities for the probe field, even in the few-photon regime. This enhancement is due to the strong dipole-dipole interactions between Rydberg atoms and the resulting excitation blockade phenomenon. In order to study such highly correlated media, ad hoc models or low-excitation assumptions are generally used to tackle their dynamical response to optical fields. Here, we study the behaviour of a cavity Rydberg-EIT setup in the non-equilibrium quantum field formalism, and we obtain analytic expressions for elastic and inelastic components of the cavity transmission spectrum, valid up to higher excitation numbers than previously achieved. This allows us to identify and interpret a polaritonic resonance structure, to our knowledge unreported so far.

quant-ph↗

arXiv2015

Quantum optical non-linearities induced by Rydberg-Rydberg interactions: a perturbative approach

In this article, we theoretically study the quantum statistical properties of the light transmitted through or reflected from an optical cavity, filled by an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. Atoms are driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of a weak signal field and a strong control beam. By using a perturbative approach, we get analytic results which remain valid in the regime of weak feeding fields, even when the intermediate state becomes resonant. Therefore they allow us to investigate quantitatively new features associated with the resonant behaviour of the system. We also propose an effective non-linear three-boson model of the system which, in addition to leading to the same analytic results as the original problem, sheds light on the physical processes at work in the system.

quant-ph↗

arXiv2014

Light storage in a room temperature atomic vapor based on coherent population oscillations

We report the experimental observation of Coherent Population Oscillation (CPO) based light storage in an atomic vapor cell at room temperature. Using the ultranarrow CPO between the ground levels of a $Λ$ system selected by polarization in metastable $^4$He, such a light storage is experimentally shown to be phase preserving. As it does not involve any atomic coherences it has the advantage of being robust to dephasing effects such as small magnetic field inhomogeneities. The storage time is limited by the population lifetime of the ground states of the $Λ$ system.

physics.atom-ph↗

arXiv2013

Quantum repeater with Rydberg blocked atomic ensembles in fiber-coupled cavities

We propose and analyze a quantum repeater architecture in which Rydberg blocked atomic ensembles inside optical cavities are linked by optical fibers. Entanglement generation, swapping and purification are achieved through collective laser manipulations of the ensembles and photon transmission. Successful transmission and storage of entanglement are heralded by ionization events rather than by photon detection signal used in previous proposals. We demonstrate how the high charge detection efficiency allows for a shortened average entanglement generation time, and we analyze an implementation of our scheme with ensembles of Cs atoms.

quant-ph↗

arXiv2013

Quantum statistics of light transmitted through an intracavity Rydberg medium

We theoretically investigate the quantum statistical properties of light transmitted through an atomic medium with strong optical non-linearity induced by Rydberg-Rydberg van der Waals interactions. In our setup, atoms are located in a cavity and non-resonantly driven on a two-photon transition from their ground state to a Rydberg level via an intermediate state by the combination of the weak signal field and a strong control beam. To characterize the transmitted light we compute the second-order correlation function $g^{\left(2\right)}\left(τ\right)$. The simulations we obtained on the specific case of rubidium atoms suggest that the bunched or antibunched nature of the outgoing beam can be chosen at will by appropriately tuning the physical parameters.

quant-ph↗

arXiv2011

Laplacian growth in self-consistent Laplacian field : Effect of the long-range interparticle interactions on the fractal dimension of structures formed by their aggregation-limited diffusion

We numerically simulate the dynamics of aggregation of interacting atomic clusters deposited on a surface. We show that the shape of the structures resulting from their aggregation-limited random walk is affected by the presence of a binary interparticle Laplacian potential due to, for instance, the surface stress field. We characterize the morphologies we obtain by their Hausdorff fractal dimension as well as the so-called external fractal dimension, which appears more sensitive to the potential. We demonstrate the relevance of our model by comparing it to previously published experimental results for antymony and silver clusters deposited onto graphite surface.

cond-mat.mes-hall↗

arXiv2009

Universal protection of unitary evolution from slow noise: dynamical control pushed to the extreme

We propose a technique that allows to simultaneously perform universal control of the evolution operator and compensate for the first order contribution of an arbitrary Hermitian constant noise. We show that, at least, a three-valued Hamiltonian is needed in order to protect the system against any such noise. This technique is illystrated by an explicit algorithm for a control sequence that is applied to numerically design a safe two-qubit gate.

quant-ph↗

arXiv2007

Discovery of very high energy gamma-ray emission in the W 28 (G6.4-0.1) region, and multiwavelength comparisons

H.E.S.S. observations of the old-age (>10^4yr; ~0.5deg diameter) composite supernova remnant (SNR) W 28 reveal very high energy (VHE) gamma-ray emission situated at its northeastern and southern boundaries. The northeastern VHE source (HESS J1801-233) is in an area where W 28 is interacting with a dense molecular cloud, containing OH masers, local radio and X-ray peaks. The southern VHE sources (HESS J1800-240 with components labelled A, B and C) are found in a region occupied by several HII regions, including the ultracompact HII region W 28A2. Our analysis of NANTEN CO data reveals a dense molecular cloud enveloping this southern region, and our reanalysis of EGRET data reveals MeV/GeV emission centred on HESS J1801-233 and the northeastern interaction region.

astro-ph↗

arXiv2007

Quantum computing with collective ensembles of multi-level systems

We propose a new physical approach for encoding and processing of quantum information in ensembles of multi-level quantum systems, where the different bits are not carried by individual particles but associated with the collective population of different internal levels. One- and two-bit gates are implemented by collective internal state transitions taking place in the presence of an excitation blockade mechanism which restricts the population of each internal state to the values zero and unity. 10-20 bit quantum computers can be built via this scheme in single trapped clouds of ground state atoms subject to the Rydberg excitation blockade mechanism, and the linear dependence between register size and the number of internal quantum states in atoms offers realistic means to reach larger registers.

quant-ph↗