arXiv subjects

Laurent de Forges de Parny

Publications and source records attributed to Laurent de Forges de Parny.

10 recordsLinked to original sources

arXiv2025

Towards a Global Scale Quantum Information Network: A Study Applied to Satellite-Enabled Distributed Quantum Computing

Recent developments have reported on the feasibility of interconnecting small quantum registers in a quantum information network of a few meter-scale for distributed quantum computing purposes. This multiple small-scale quantum processors communicating and cooperating to execute computational tasks is considered as a promising solution to the scalability problem of reaching more than thousands of noise-free qubits. Here, we propose and assess a satellite-enabled distributed quantum computing system at the French national scale, based on existing infrastructures in Paris and Nice. We consider a system composed of both a ground and a space segment, allowing for the distribution of end-to-end entanglement between Alice in Paris and Bob in Nice, each owning a few-qubit processor composed of trapped ions. In the context of quantum computing, this entanglement resource can be used for the teleportation of a qubit state or for gate teleportation. We numerically assess the entanglement distribution rate and fidelity generated by this space-based quantum information network, and discuss concrete use cases and service performance levels in the framework of distributed quantum computing.

quant-ph↗

arXiv2025

The Role of the Satellite in Quantum Information Networks

Quantum Information Networks (QIN) attract increasing interest, as they will enable interconnection of multiple quantum devices in a distributed organization thus enhancing intrinsic computing, sensing, and security capabilities. The core mechanism of a QIN is quantum state swapping, based on teleportation, which consumes quantum entanglement, and which can be seen in this context as a new kind of network resource. The satellite is expected to play a central role for supporting global connectivity in such novel networks in which ground fiber links have stringent restrictions in length due to the absorption losses in optical fibers. There is indeed fundamental limits in the maximal fiber links distance which may not be exceeded for any unitary links. In this paper we clarify our motivations to develop such networks with satellites, and we discuss their associated use cases based on entanglement distribution, and we present the future potential users. We also assess quantitatively the ranges for which the satellite becomes mandatory in quantum information networks.

quant-ph↗

arXiv2025

Entanglement Management in Space-Based Quantum Information Networks

With the evolution of quantum computing, quantum sensing and secure quantum communication protocols, the demand for global development of Quantum Information Networks (QIN) has become crucial. Satellites play an indispensable role in enabling connectivity across vast distances, transcending terrestrial limitations. In this article, we explore various ways in which satellites may be involved in the deployment of these novel networks from their integration into the network architecture to the challenges they face.

quant-ph↗

arXiv2023

Satellite-based Quantum Information Networks: Use cases, Architecture, and Roadmap

Quantum Information Networks (QINs) attract increasing interest, as they enable connecting quantum devices over long distances, thus greatly enhancing their intrinsic computing, sensing, and security capabilities. The core mechanism of a QIN is quantum state teleportation, consuming quantum entanglement, which can be seen in this context as a new kind of network resource. Here we identify use cases per activity sector, including key performance targets, as a reference for the network requirements. We then define a high-level architecture of a generic QIN, before focusing on the architecture of the Space segment, with the aim of identifying the main design drivers and critical elements. A survey of the state-of-the-art of these critical elements is presented, as are issues related to standardisation. Finally, we explain our roadmap to developing the first QINs and detail the already concluded first step, the design and numerical simulation of a Space-to-ground entanglement distribution demonstrator.

quant-ph↗

arXiv2021

Magnetic Phase Transition in the Ground-State Phase Diagram of Binary Bose Gases in Optical Lattices

We investigate the ground-state phase diagram of interacting binary Bose gases trapped in two-dimensional optical lattices by means of quantum Monte Carlo simulations. Our simulations reveal a magnetic phase transition from a $x-y$ ferromagnetic-order to a spin insulator inside the Mott insulating phase with two particles per site for quasi-balanced on-site inter- and intra-particle interactions, i.e., $U_{\uparrow \downarrow} \lesssim U$. This 3D-XY transition is characterized by the establishment of a finite local magnetic moment along the $z$-axis, ferromagnetic correlations in the $x-y$ plan and by counterflow superfluidity inside the Mott phase. When decreasing $U_{\uparrow \downarrow}/U$, this transition merges with the Mott-superfluid transition and becomes first-order. The merging of the two transitions is investigated with respect to $U_{\uparrow \downarrow}/U$ parameter.

cond-mat.quant-gas↗

arXiv2020

Spectral Structure and Many-Body Dynamics of Ultracold Bosons in a Double-Well

We examine the spectral structure and many-body dynamics of two and three repulsively interacting bosons trapped in a one-dimensional double-well, for variable barrier height, inter-particle interaction strength, and initial conditions. By exact diagonalization of the many-particle Hamiltonian, we specifically explore the dynamical behaviour of the particles launched either at the single particle ground state or saddle point energy, in a time-independent potential. We complement these results by a characterisation of the cross-over from diabatic to quasi-adiabatic evolution under finite-time switching of the potential barrier, via the associated time-evolution of a single particle's von Neumann entropy. This is achieved with the help of the multiconfigurational time-dependent Hartree method for indistinguishable particles (\textsc{Mctdh-x}) -- which also allows us to extrapolate our results for increasing particle numbers.

quant-ph↗

arXiv2018

Phase Diagrams of Antiferromagnetic Spin-1 Bosons on Square Optical Lattice with the Quadratic Zeeman Effect

We study the quadratic Zeeman effect (QZE) in a system of antiferromagnetic spin-1 bosons on a square lattice and derive the ground-state phase diagrams by means of quantum Monte Carlo simulations and mean field treatment. The QZE imbalances the populations of the magnetic sublevels $σ=\pm1$ and $σ=0$, and therefore affects the magnetic and mobility properties of the phases. Both methods show that the tip of the even Mott lobes, stabilized by singlet state, is destroyed when turning on the QZE, thus leaving the space to the superfluid phase. Contrariwise, the tips of odd Mott lobes remain unaffected. Therefore, the Mott-superfluid transition with even filling strongly depends on the strength of the QZE, and we show that the QZE can act as a control parameter for this transition at fixed hopping. Using quantum Monte Carlo simulations, we elucidate the nature of the phase transitions and examine in detail the nematic order: the first-order Mott-superfluid transition with even filling observed in the absence of QZE becomes second order for weak QZE, in contradistinction to our mean-field results which predict a first-order transition in a larger range of QZE. Furthermore, a spin nematic order with director along the $z$ axis is found in the odd Mott lobes and in the superfluid phase for energetically favored $σ=\pm1$ states. In the superfluid phase with even filling, the $xy$ components of the nematic director remain finite only for moderate QZE.

cond-mat.quant-gas↗

arXiv2017

Quantum and Thermal Phase Transitions in a Bosonic Atom-Molecule Mixture in a Two-dimensional Optical Lattice

We study the ground state and the thermal phase diagram of a two-species Bose-Hubbard model, with $U(1)\times \mathbb{Z}_2$ symmetry, describing atoms and molecules on a 2D optical lattice interacting via a Feshbach resonance. Using quantum Monte Carlo simulations and mean field theory, we show that the conversion between the two-species, coherently coupling the atomic and molecular states, has a crucial impact on the Mott-Superfluid transition and stabilizes an insulating phase with a gap controlled by the conversion term -- \textit{the Feshbach insulator} -- instead of a standard Mott insulating phase. Depending on the detuning between atoms and molecules, this model exhibits three phases: the Feshbach insulator, a molecular condensate coexisting with non condensed atoms and a mixed atomic-molecular condensate. Employing a finite-size scaling method, we observe 3D XY (3D Ising) transition when $U(1)$ ($ \mathbb{Z}_2$) is broken whereas the transition is first-order when both $U(1)$ and $ \mathbb{Z}_2$ symmetries are spontaneously broken. The finite temperature phase diagram is also discussed. The thermal disappearance of the molecular superfluid leads to a Berezinskii-Kosterlitz-Thouless transition with unusual universal jump in the superfluid density. The loss of the quasi-long-range coherence of the mixed atomic and molecular superfluid is more subtle since only atoms exhibit conventional Berezinskii-Kosterlitz-Thouless criticality. We also observe a classical first-order transition between the mixed superfluid and the normal Bose liquid at low temperature.

cond-mat.quant-gas↗

arXiv2015

Multiple Transitions of Coupled Atom-Molecule Bosonic Mixtures in Two Dimensions

Motivated by the physics of coherently coupled, ultracold atom-molecule mixtures, we investigate a classical model possessing the same symmetry -- namely a $U(1)\times \mathbb{Z}_2$ symmetry, associated with the mass conservation in the mixture ($U(1)$ symmetry), times the $\mathbb{Z}_2$ symmetry in the phase relationship between atoms and molecules. In two spatial dimensions the latter symmetry can lead to a finite-temperature Ising transition, associated with (quasi) phase locking between the atoms and the molecules. On the other hand, the $U(1)$ symmetry has an associated Berezinskii-Kosterlitz-Thouless (BKT) transition towards quasi-condensation of atoms or molecules. The existence of the two transitions is found to depend crucially on the population imbalance (or detuning) between atoms and molecules: when the molecules are majority in the system, their BKT quasi-condensation transition occurs at a higher temperature than that of the atoms; the latter has the unconventional nature of an Ising (quasi) phase-locking transition, lacking a finite local order parameter below the critical temperature. When the balance is gradually biased towards the atoms, the two transitions merge together to leave out a unique BKT transition, at which both atoms and molecules acquire quasi-long-range correlations, but only atoms exhibit conventional BKT criticality, with binding of vortex-antivortex pairs into short-range dipoles. The molecular vortex-antivortex excitations bind as well, but undergo a marked crossover from a high-temperature regime in which they are weakly bound, to a low-temperature regime of strong binding, reminiscent of their transition in the absence of atom-molecule coupling.

cond-mat.quant-gas↗

arXiv2015

Feshbach-Stabilized Insulator of Bosons in Optical Lattices

Feshbach resonances - namely resonances between an unbound two-body state (atomic state) and a bound (molecular) state, differing in magnetic moment - are a unique tool to tune the interaction properties of ultracold atoms. Here we show that the spin-changing interactions, coherently coupling the atomic and molecular state, can act as a novel mechanism to stabilize an insulating phase - the Feshbach insulator - for bosons in an optical lattice close to a narrow Feshbach resonance. Making use of quantum Monte Carlo simulations and mean-field theory, we show that the Feshbach insulator appears around the resonance, preventing the system from collapsing when the effective atomic scattering length becomes negative. On the atomic side of the resonance, the transition from condensate to Feshbach insulator has a characteristic first-order nature, due to the simultaneous loss of coherence in the atomic and molecular components. These features appear clearly in the ground-state phase diagram of e.g. $^{87}$Rb around its 414 G resonance, and they are therefore directly amenable to experimental observation.

cond-mat.quant-gas↗