Showing 1–28 of 28 results for author: Morassi, M

Crossing over universal scaling laws in two-dimensional driven dissipative condensates

Authors: Q. Fontaine, F. Helluin, M. Escalera, D. Pinto Dias, A. Lemaître, M. Morassi, M. Wouters, A. Minguzzi, L. Canet, S. Ravets, J. Bloch

Abstract: In low dimensional systems, fluctuations are enhanced and prevent the spontaneous breaking of continuous symmetries. As a result, spatial and temporal correlation functions decay at large distances and long times. A well established example is given by two-dimensional bosonic condensates at equilibrium, which do not display long-range order of the coherence but algebraic decay belonging to the Ber… ▽ More In low dimensional systems, fluctuations are enhanced and prevent the spontaneous breaking of continuous symmetries. As a result, spatial and temporal correlation functions decay at large distances and long times. A well established example is given by two-dimensional bosonic condensates at equilibrium, which do not display long-range order of the coherence but algebraic decay belonging to the Berezinski-Kosterlitz-Thouless universality class. In contrast, the universal behaviors of non-equilibrium bosonic condensates are more diverse and many open questions remain. Here, we explore the spatio-temporal coherence properties of two-dimensional driven-dissipative polariton condensates in semiconductor optical microcavities. By tuning microscopic parameters, we observe a cross-over between two scaling laws that we attribute to the Edwards-Wilkinson (EW) and the Kardar-Parisi-Zhang (KPZ) universality classes. We demonstrate the collapse of the measured first-order correlations onto the EW and KPZ universal scaling functions and obtain critical exponents, well matching the values predicted theoretically. Our results highlight the intrinsic non-equilibrium nature of polariton condensates and establish them as a platform of choice for controlled exploration of the two-dimensional KPZ universality class. △ Less

Submitted 7 August, 2026; originally announced August 2026.

Industry-ready spin-photon interfaces for hybrid photonic quantum computing

Authors: Hêlio Huet, Hubert Lam, Thibaut Pollet, Petr Steindl, Alice Bernard, Albert Adiyatullin, Petr Stepanov, William Hease, Victor Guilloux, Nico Margaria, Joris Verstraten, Raksha Singla, Samuel T. Mister, Anton Pishchagin, Lara Couronné, Samuel Huber, David Sebastian, Duc Duy Tran, Thi Hao Nhi Nguyen, Thi Phuong Do, Joseph Sulpizio, Yann Portella, Kiarn T. Laverick, Thinhinane Bennour, Tomas Alexandre De Sousa , et al. (23 additional authors not shown)

Abstract: Hybrid photonic quantum computers, combining stationary matter qubits and flying photonic qubits, offer an intrinsically networked and resource-efficient route to large-scale, error-corrected quantum computation. Their core components are cavity-coupled matter qubits that act as light--matter interfaces, enabling: high-efficiency on-demand single-photon generation, stable near-unity photon indisti… ▽ More Hybrid photonic quantum computers, combining stationary matter qubits and flying photonic qubits, offer an intrinsically networked and resource-efficient route to large-scale, error-corrected quantum computation. Their core components are cavity-coupled matter qubits that act as light--matter interfaces, enabling: high-efficiency on-demand single-photon generation, stable near-unity photon indistinguishability and spin--multi-photon entanglement. Semiconductor quantum dots in microcavities are a leading platform for realizing such devices. Yet reaching the performance, reproducibility and spin-coherence thresholds for large-scale error correction remains a major challenge requiring industrial fabrication and control. Here we report thousands of monolithic semiconductor quantum-dot devices fabricated using a III--V pilot production-line process compatible with large-scale deployment. Systematic control of source parameters yields state-of-the-art efficiency and supports a path to optical losses below fault-tolerance thresholds. Using field-quadrature state reconstruction as a stringent joint test of efficiency and indistinguishability, we observe near-unity photon quantum purity stable over tens of minutes and a record single-photon Wigner-function negativity. We further demonstrate seven-partite spin--multi-photon entanglement and spin coherence extendable to microsecond timescales in the low-magnetic-field regime. Finally, photons from distant sources are as indistinguishable as photons emitted successively by a single source. These results establish foundry-compatible III--V quantum dots as a scalable platform for hybrid photonic quantum computing. △ Less

Submitted 14 July, 2026; v1 submitted 26 June, 2026; originally announced June 2026.

Comments: 11 pages, 4 figures

Coupled Topological Interface States and Phonon Molecules in GaAs/AlAs Superlattices

Authors: S. Sandeep, O. Colmegna, C. Xiang, E. R. Cardozo de Oliveira, K. Papatryfonos, M. Morassi, A. Lemaitre, N. D. Lanzillotti-Kimura

Abstract: Topological interface states in one-dimensional superlattices provide spatially localized phonon modes protected by the topology of the underlying band structure. In GaAs/AlAs distributed Bragg reflectors (DBRs), such states can be engineered through band inversion between superlattices with opposite Zak phases within the Su-Schrieffer-Heeger (SSH) framework. Here, we demonstrate topological phono… ▽ More Topological interface states in one-dimensional superlattices provide spatially localized phonon modes protected by the topology of the underlying band structure. In GaAs/AlAs distributed Bragg reflectors (DBRs), such states can be engineered through band inversion between superlattices with opposite Zak phases within the Su-Schrieffer-Heeger (SSH) framework. Here, we demonstrate topological phonon molecules and extended chains formed by coupled nanophononic interface states. By concatenating three superlattices with alternating topology, we realize two coupled interface states that hybridize into symmetric and antisymmetric modes, whose splitting can be tuned over tens of gigahertz by varying the reflectivity of the central DBR. Extending this concept, we engineer chains of up to N=6 coupled interface states that form narrow topological minibands while remaining strongly localized at the interfaces. We experimentally observe these coupled states in molecular-beam-epitaxy-grown GaAs/AlAs heterostructures using time-domain pump-probe transient reflectivity measurements, and reproduce their behavior using transfer-matrix calculations and a simple analytical model for the mode splitting. These results establish topological interface states as a robust platform for engineering coupled phononic systems and tunable nanophononic architectures in the GHz regime. △ Less

Submitted 12 May, 2026; originally announced May 2026.

Emission of time-ordered photon pairs from a coherently-driven Kerr microcavity

Authors: Ferdinand Claude, Yueguang Zhou, Sylvain Ravets, Jacqueline Bloch, Martina Morassi, Aristide Lemaître, Alberto Bramati, Anna Minguzzi, Iacopo Carusotto, Irénée Frérot, Maxime Richard

Abstract: Weakly-interacting many-body systems possess remarkable quantum properties that are essential components of quantum technologies, and constitute a topic of fundamental interest. Here we show that in a solid-state nonlinear microcavity embedding discrete modes of exciton-dressed photons, we can isolate a single eigenmode of quantum fluctuations from the much brighter coherent fraction of the field.… ▽ More Weakly-interacting many-body systems possess remarkable quantum properties that are essential components of quantum technologies, and constitute a topic of fundamental interest. Here we show that in a solid-state nonlinear microcavity embedding discrete modes of exciton-dressed photons, we can isolate a single eigenmode of quantum fluctuations from the much brighter coherent fraction of the field. In this regime, we perform frequency- and time-resolved correlations measurements between photons on the red and blue side of the fluctuations spectrum. When the average number of fluctuation quanta is smaller than one, we observe the formation of large pairwise time-ordered correlations: red photon first and blue photon second. We show that this peculiar time-ordering correlation emerges spontaneously from the interplay between frequency-resolved detection, and the non-trivial internal quantum structure of the elementary fluctuations. △ Less

Submitted 11 June, 2026; v1 submitted 10 January, 2026; originally announced January 2026.

Comments: 11 pages, 3 figures, plus 9 pages of supplementary material

Tailoring quantum walks in integrated photonic lattices

Authors: A. Raymond, P. Cathala, M. Morassi, A. Lemaître, F. Raineri, S. Ducci, F. Baboux

Abstract: Unlike discrete photonic circuits, which manipulate photons step-by-step using a series of optical elements, arrays of coupled waveguides enable photons to interfere continuously across the entire structure. When composed of a nonlinear material, such arrays can also directly generate quantum states of light within the circuit. To clarify the similarities and distinctions between these two approac… ▽ More Unlike discrete photonic circuits, which manipulate photons step-by-step using a series of optical elements, arrays of coupled waveguides enable photons to interfere continuously across the entire structure. When composed of a nonlinear material, such arrays can also directly generate quantum states of light within the circuit. To clarify the similarities and distinctions between these two approaches of quantum walks, we conduct here a systematic comparison between linear waveguide arrays, injected with photons produced externally, and nonlinear arrays, where photon pairs are continuously generated via parametric down-conversion. We experimentally validate these predictions using III-V semiconductor nonlinear waveguide lattices with varied geometries, enabling us to tune the depth of the quantum walks over an order of magnitude and reveal the gradual emergence of non-classicality in the output state. Finally, we demonstrate an inverse-design approach to engineer \textit{aperiodic} waveguide arrays, whose optimized coupling profiles generate maximally entangled states such as the biphoton W-state. These results highlight the potential of continuously-coupled photonic systems to harness high-dimensional entanglement within compact architectures. △ Less

Submitted 12 December, 2025; originally announced December 2025.

Comments: 17 pages

Journal ref: Optics Express 33, 45869 (2025)

Biphoton state generation and engineering with bright hybrid III-V/Silicon photonic devices

Authors: Lorenzo Lazzari, Jérémie Schuhmann, Othmane Meskine, Martina Morassi, Aristide Lemaître, Maria I. Amanti, Frédéric Boeuf, Fabrice Raineri, Florent Baboux, Sara Ducci

Abstract: Hybrid photonic circuits, harnessing the complementary strengths of multiple materials, represent a key resource to enable compact, scalable platforms for quantum technologies. In particular, the availability of bright sources of tunable biphoton states is eagerly awaited to meet the variety of applications currently under development. In this work we demonstrate a heterogeneously integrated devic… ▽ More Hybrid photonic circuits, harnessing the complementary strengths of multiple materials, represent a key resource to enable compact, scalable platforms for quantum technologies. In particular, the availability of bright sources of tunable biphoton states is eagerly awaited to meet the variety of applications currently under development. In this work we demonstrate a heterogeneously integrated device that merges biphoton generation and on-chip quantum state engineering, combining an AlGaAs photon-pair source with a CMOS-compatible silicon-on-insulator (SOI) circuit. Photon pairs are generated in the C telecom band via spontaneous parametric down-conversion and transferred to the SOI chip through a multimode evanescent coupling scheme. This design achieves a pair generation rate above 10$^{6}$ s$^{-1}$mW$^{-1}$ and a coincidence-to-accidental ratio up to 600. Crucially, the coupling design induces strong and predictable transformations of the biphoton joint spectral amplitude, enabling complex quantum state engineering entirely on-chip in a compact device compliant with electrical pumping. △ Less

Submitted 10 November, 2025; originally announced November 2025.

Measuring non-Abelian quantum geometry and topology in a multi-gap photonic lattice

Authors: Martin Guillot, Cédric Blanchard, Martina Morassi, Aristide Lemaître, Luc Le Gratiet, Abdelmounaim Harouri, Isabelle Sagnes, Robert-Jan Slager, F. Nur Ünal, Jacqueline Bloch, Sylvain Ravets

Abstract: Recent discoveries in semi-metallic multi-gap systems featuring band singularities have galvanized enormous interest in particular due to the emergence of non-Abelian braiding properties of band nodes. This previously uncharted set of topological phases necessitates novel approaches to probe them in laboratories, a pursuit that intricately relates to evaluating non-Abelian generalizations of the A… ▽ More Recent discoveries in semi-metallic multi-gap systems featuring band singularities have galvanized enormous interest in particular due to the emergence of non-Abelian braiding properties of band nodes. This previously uncharted set of topological phases necessitates novel approaches to probe them in laboratories, a pursuit that intricately relates to evaluating non-Abelian generalizations of the Abelian quantum geometric tensor (QGT) that characterizes geometric responses. Here, we pioneer the direct measurement of the non-Abelian QGT. We achieve this by implementing a novel orbital-resolved polarimetry technique to probe the full Bloch Hamiltonian of a six-band two-dimensional (2D) synthetic lattice, which grants direct experimental access to non-Abelian quaternion charges, the Euler curvature, and the non-Abelian quantum metric associated with all bands. Quantum geometry has been highlighted to play a key role on macroscopic phenomena ranging from superconductivity in flat-bands, to optical responses, transport, metrology, and quantum Hall physics. Therefore, our work unlocks the experimental probing of a wide phenomenology of multi-gap systems, at the confluence of topology, geometry and non-Abelian physics. △ Less

Submitted 8 April, 2026; v1 submitted 5 November, 2025; originally announced November 2025.

Topological protection of photon-pair generation in nonlinear waveguide arrays

Authors: A. Zecchetto, J. -R. Coudevylle, M. Morassi, A. Lemaître, M. I. Amanti, S. Ducci, F. Baboux

Abstract: Harnessing topological effects offers a promising route to protect quantum states of light from imperfections, potentially enabling more robust platforms for quantum information processing. This capability is particularly relevant for active photonic circuits that generate quantum light directly on-chip. Here, we explore topological effects on photon-pair generation via spontaneous parametric down… ▽ More Harnessing topological effects offers a promising route to protect quantum states of light from imperfections, potentially enabling more robust platforms for quantum information processing. This capability is particularly relevant for active photonic circuits that generate quantum light directly on-chip. Here, we explore topological effects on photon-pair generation via spontaneous parametric down-conversion (SPDC) in nonlinear waveguide arrays, both theoretically and experimentally. A systematic comparison of homogeneous, trivial, and topological Su-Schrieffer-Heeger arrays reveals that only the topological configuration preserves a stable SPDC resonance spectrum under disorder in the tunnel couplings, with fluctuations in the resonance position reduced by more than one order of magnitude. An analytical model supports our experimental observations by linking this robustness to the band-structure properties of the interacting modes. These findings establish quadratic nonlinear waveguide arrays as a promising platform to explore the interplay of nonlinearity, topology, and disorder in quantum photonic circuits. △ Less

Submitted 27 October, 2025; originally announced October 2025.

All-optical nonlinear phase modulation in open semiconductor microcavities

Authors: Fedor A. Benimetskiy, Paul M. Walker, Anthony Ellul, Oleksandr Kyriienko, Martina Morassi, Aristide Lemaître, Tommi Isoniemi, Maurice S. Skolnick, Jacqueline Bloch, Sylvain Ravets, Dmitry N. Krizhanovskii

Abstract: We report a significant advancement in ultra low power light-by-light phase modulation using open semiconductor microcavities in the strong light-matter coupling regime. We achieve cross-phase modulation of up to 247$\pm$17 mrad per particle between laser beams attenuated to single-photon average intensities. This breakthrough extends the potential for quantum information processing and nonlinear… ▽ More We report a significant advancement in ultra low power light-by-light phase modulation using open semiconductor microcavities in the strong light-matter coupling regime. We achieve cross-phase modulation of up to 247$\pm$17 mrad per particle between laser beams attenuated to single-photon average intensities. This breakthrough extends the potential for quantum information processing and nonlinear quantum optics in strongly coupled light-matter systems, setting a new benchmark in the field without relying on atom-like emitters. Our findings suggest promising new avenues for scalable quantum optical technologies. △ Less

Submitted 21 July, 2026; v1 submitted 6 October, 2025; originally announced October 2025.

A sublattice Stokes polarimeter for bipartite photonic lattices

Authors: Martin Guillot, Cédric Blanchard, Nicolas Pernet, Martina Morassi, Aristide Lemaître, Luc Le Gratiet, Abdelmounaim Harouri, Isabelle Sagnes, Jacqueline Bloch, Sylvain Ravets

Abstract: The concept of pseudo-spin provides a general framework for describing physical systems featuring two-component spinors, including light polarization, sublattice degrees of freedom in bipartite lattices, and valley polarization in 2D materials. In all cases, the pseudo-spin can be mapped to a Stokes vector on the Poincaré sphere. Stokes polarimeters for measuring the polarization of light are a po… ▽ More The concept of pseudo-spin provides a general framework for describing physical systems featuring two-component spinors, including light polarization, sublattice degrees of freedom in bipartite lattices, and valley polarization in 2D materials. In all cases, the pseudo-spin can be mapped to a Stokes vector on the Poincaré sphere. Stokes polarimeters for measuring the polarization of light are a powerful tool with a wide range of applications both in classical and quantum science. Generalizing Stokes polarimetry to other spinor degrees of freedom is thus a challenge of prime importance. Here, we introduce and demonstrate a Stokes polarimeter for the sublattice polarization in a bipartite photonic lattice. Our method relies on k-space photoluminescence intensity measurements under controlled phase shifts and attenuations applied independently to each sublattice. We implement our method using honeycomb arrays of coupled microcavities realizing photonic analogs of graphene and hexagonal boron nitride. Using our sublattice polarimeter, we reconstruct the Bloch modes in amplitude and phase across the Brillouin zone, achieving sub-linewidth precision in the determination of their eigenenergies, including near band touching points. This enables full access to the system Bloch Hamiltonian and quantum geometric tensor. Our approach can readily be extended to more complex systems with additional internal degrees of freedom, enabling experimental investigations of trigonal warping, Chern insulating phases, and Euler-class topology in multigap systems. △ Less

Submitted 22 July, 2025; originally announced July 2025.

Optical and magnetic response by design in GaAs quantum dots

Authors: Christian Schimpf, Ailton J. Garcia Jr., Zhe X. Koong, Giang N. Nguyen, Lukas L. Niekamp, Martin Hayhurst Appel, Ahmed Hassanen, James Waller, Yusuf Karli, Saimon Philipe Covre da Silva, Julian Ritzmann, Hans-Georg Babin, Andreas D. Wieck, Anton Pishchagin, Nico Margaria, Ti-Huong Au, Sebastien Bossier, Martina Morassi, Aristide Lemaitre, Pascale Senellart, Niccolo Somaschi, Arne Ludwig, Richard Warburton, Mete Atatüre, Armando Rastelli , et al. (2 additional authors not shown)

Abstract: Quantum networking technologies use spin qubits and their interface to single photons as core components of a network node. This necessitates the ability to co-design the magnetic- and optical-dipole response of a quantum system. These properties are notoriously difficult to design in many solid-state systems, where spin-orbit coupling and the crystalline environment for each qubit create inhomoge… ▽ More Quantum networking technologies use spin qubits and their interface to single photons as core components of a network node. This necessitates the ability to co-design the magnetic- and optical-dipole response of a quantum system. These properties are notoriously difficult to design in many solid-state systems, where spin-orbit coupling and the crystalline environment for each qubit create inhomogeneity of electronic g-factors and optically active states. Here, we show that GaAs quantum dots (QDs) obtained via the quasi-strain-free local droplet etching epitaxy growth method provide spin and optical properties predictable from assuming the highest possible QD symmetry. Our measurements of electron and hole g-tensors and of transition dipole moment orientations for charged excitons agree with our predictions from a multiband k.p simulation constrained only by a single atomic-force-microscopy reconstruction of QD morphology. This agreement is verified across multiple wavelength-specific growth runs at different facilities within the range of 730 nm to 790 nm for the exciton emission. Remarkably, our measurements and simulations track the in-plane electron g-factors through a zero-crossing from -0.1 to 0.3 and linear optical dipole moment orientations fully determined by an external magnetic field. The robustness of our results demonstrates the capability to design - prior to growth - the properties of a spin qubit and its tunable optical interface best adapted to a target magnetic and photonic environment with direct application for high-quality spin-photon entanglement. △ Less

Submitted 3 April, 2025; originally announced April 2025.

The impact of hole $g$-factor anisotropy on spin-photon entanglement generation with InGaAs quantum dots

Authors: P. R. Ramesh, E. Annoni, N. Margaria, D. A. Fioretto, A. Pishchagin, M. Morassi, A. Lemaître, M. F. Doty, P. Senellart, L. Lanco, N. Belabas, S. C. Wein, O. Krebs

Abstract: Self-assembled InGaAs/GaAs quantum dots (QDs) are of particular importance for the deterministic generation of spin-photon entanglement. One promising scheme relies on the Larmor precession of a spin in a transverse magnetic field, which is governed by the in-plane $g$-factors of the electron and valence band heavy-hole. We probe the origin of heavy-hole $g$-factor anisotropy with respect to the i… ▽ More Self-assembled InGaAs/GaAs quantum dots (QDs) are of particular importance for the deterministic generation of spin-photon entanglement. One promising scheme relies on the Larmor precession of a spin in a transverse magnetic field, which is governed by the in-plane $g$-factors of the electron and valence band heavy-hole. We probe the origin of heavy-hole $g$-factor anisotropy with respect to the in-plane magnetic field direction and uncover how it impacts the entanglement generated between the spin and the photon polarization. First, using polarization-resolved photoluminescence measurements on a single QD, we determine that the impact of valence-band mixing dominates over effects due to a confinement-renormalized cubic Luttinger $q$ parameter. From this, we construct a comprehensive hole $g$-tensor model. We then use this model to simulate the concurrence and fidelity of spin-photon entanglement generation with anisotropic hole $g$-factors, which can be tuned via magnetic field angle and excitation polarization. The results demonstrate that post-growth control of the hole $g$-factor can be used to improve spin-photon cluster state generation. △ Less

Submitted 9 June, 2025; v1 submitted 11 February, 2025; originally announced February 2025.

Excitonic oscillator-strength saturation dominates polariton-polariton interactions

Authors: Maxime Richard, Irénée Frérot, Sylvain Ravets, Jacqueline Bloch, Carlos Anton-Solanas, Ferdinand Claude, Yueguang Zhou, Martina Morassi, Aristide Lemaître, Iacopo Carusotto, and Anna Minguzzi

Abstract: Exciton-polaritons in semiconductor microcavities exhibit large two-body interactions that, thanks to ever refined nanotechnology techniques, are getting closer and closer to the quantum regime where single-photon nonlinearities start being relevant. To foster additional progress in this direction, in this work we experimentally investigate the microscopic mechanism driving polariton-polariton int… ▽ More Exciton-polaritons in semiconductor microcavities exhibit large two-body interactions that, thanks to ever refined nanotechnology techniques, are getting closer and closer to the quantum regime where single-photon nonlinearities start being relevant. To foster additional progress in this direction, in this work we experimentally investigate the microscopic mechanism driving polariton-polariton interactions. We measure the dispersion relation of the collective excitations that are thermally generated on top of a coherent fluid of interacting lower-polaritons. By comparing the measurements with the Bogoliubov theory over both the lower and upper polariton branches simultaneously, we find that polariton-polariton interactions stem dominantly from a mechanism of saturation of the exciton oscillator strength. △ Less

Submitted 14 January, 2025; originally announced January 2025.

Energy-efficient picosecond spin-orbit torque magnetization switching in ferro- and ferrimagnetic films

Authors: Eva Díaz, Alberto Anadón, Pablo Olleros-Rodríguez, Harjinder Singh, Héloïse Damas, Paolo Perna, Martina Morassi, Aristide Lemaître, Michel Hehn, Jon Gorchon

Abstract: Electrical current pulses can be used to manipulate magnetization efficiently via spin-orbit torques (SOTs). Pulse durations as short as a few picoseconds have been used to switch the magnetization of ferromagnetic films, reaching the THz regime. However, little is known about the reversal mechanisms and energy requirements in the ultrafast switching regime. In this work, we quantify the energy co… ▽ More Electrical current pulses can be used to manipulate magnetization efficiently via spin-orbit torques (SOTs). Pulse durations as short as a few picoseconds have been used to switch the magnetization of ferromagnetic films, reaching the THz regime. However, little is known about the reversal mechanisms and energy requirements in the ultrafast switching regime. In this work, we quantify the energy cost for magnetization reversal over 7 orders of magnitude in pulse duration, in both ferromagnetic and ferrimagnetic samples, bridging quasi-static spintronics and femtomagnetism. To this end, we develop a method to stretch picosecond pulses generated by a photoconductive switch by an order of magnitude. Thereby, we can create current pulses from picoseconds to durations approaching pulse width available with commercial instruments. We show that the energy cost for SOT switching decreases by more than an order of magnitude in all samples when the pulse duration enters the picosecond range. We project an energy cost of 9 fJ for a 100 x 100 nm 2 ferrimagnetic device. Micromagnetic and macrospin simulations unveil a transition from a non-coherent to a coherent magnetization reversal with a strong modification of the magnetization dynamical trajectories as pulse duration is reduced. Our results cement the potential for high-speed magnetic spin-orbit torque memories and highlights alternative magnetization reversal pathways at fast time scales. △ Less

Submitted 1 October, 2024; originally announced October 2024.

Comments: Nature Nanotechnology, 2024

Interference of ultrahigh frequency acoustic phonons from distant quasi-continuous sources

Authors: C. Xiang, E. R. Cardozo de Oliveira, S. Sandeep, K. Papatryfonos, M. Morassi, L. Le Gratiet, A. Harouri, I. Sagnes, A. Lemaitre, O. Ortiz, M. Esmann, N. D. Lanzillotti-Kimura

Abstract: The generation of propagating acoustic waves is essential for telecommunication applications, quantum technologies, and sensing. Up to now, the electrical generation has been at the core of most implementations, but is technologically limited to a few gigahertz. Overcoming this frequency limit holds the prospect of faster modulators, quantum acoustics at higher working temperatures, nanoacoustic s… ▽ More The generation of propagating acoustic waves is essential for telecommunication applications, quantum technologies, and sensing. Up to now, the electrical generation has been at the core of most implementations, but is technologically limited to a few gigahertz. Overcoming this frequency limit holds the prospect of faster modulators, quantum acoustics at higher working temperatures, nanoacoustic sensing from smaller volumes. Alternatively, the optical excitation of acoustic resonators has unlocked frequencies up to 1 THz, but in most cases, the acoustic energy cannot be efficiently extracted from the resonator into a propagating wave. Here, we demonstrate a quasi-continuous and coherent source of 20 GHz acoustic phonons, based on a ridge waveguide, structured in the vertical direction as a high-Q acousto-optic resonator. The high frequency phonons propagate up to 20 $μ$m away from the source, with a decay rate of $\sim$1.14 dB/$μ$m. We demonstrate the coherence between acoustic phonons generated from two distant sources through spatio-temporal interference. This concept could be scaled up to a larger number of sources, which enable a new generation of optically programmed, reconfigurable nanoacoustic devices and applications. △ Less

Submitted 9 July, 2024; originally announced July 2024.

Tunable Generation of Spatial Entanglement in Nonlinear Waveguide Arrays

Authors: A. Raymond, A. Zecchetto, J. Palomo, M. Morassi, A. Lemaître, F. Raineri, M. I. Amanti, S. Ducci, F. Baboux

Abstract: Harnessing high-dimensional entangled states of light presents a frontier for advancing quantum information technologies, from fundamental tests of quantum mechanics to enhanced computation and communication protocols. In this context, the spatial degree of freedom stands out as particularly suited for on-chip integration. But while traditional demonstrations produce and manipulate path-entangled… ▽ More Harnessing high-dimensional entangled states of light presents a frontier for advancing quantum information technologies, from fundamental tests of quantum mechanics to enhanced computation and communication protocols. In this context, the spatial degree of freedom stands out as particularly suited for on-chip integration. But while traditional demonstrations produce and manipulate path-entangled states sequentially with discrete optical elements, continuously-coupled nonlinear waveguide systems offer a promising alternative where photons can be generated and interfere along the entire propagation length, unveiling novel capabilities within a reduced footprint. Here we exploit this concept to implement a compact and reconfigurable source of path-entangled photon pairs based on parametric down-conversion in semiconductor nonlinear waveguides arrays. We use a double-pump configuration to engineer the output quantum state and implement various types of spatial correlations, exploiting a quantum interference effect between the biphoton state generated in each pumped waveguide. This demonstration, at room temperature and telecom wavelength, illustrates the potential of continuously-coupled systems as a promising alternative to discrete multi-component quantum circuits for leveraging the high-dimensional spatial degree of freedom of photons. △ Less

Submitted 9 December, 2024; v1 submitted 13 May, 2024; originally announced May 2024.

Journal ref: Phys. Rev. Lett. 133, 233602 (2024)

Hybrid III-V/Silicon Quantum Photonic Device Generating Broadband Entangled Photon Pairs

Authors: J. Schuhmann, L. Lazzari, M. Morassi, A. Lemaitre, I. Sagnes, G. Beaudoin, M. I. Amanti, F. Boeuf, F. Raineri, F. Baboux, S. Ducci

Abstract: The demand for integrated photonic chips combining the generation and manipulation of quantum states of light is steadily increasing, driven by the need for compact and scalable platforms for quantum information technologies. While photonic circuits with diverse functionalities are being developed in different single material platforms, it has become crucial to realize hybrid photonic circuits tha… ▽ More The demand for integrated photonic chips combining the generation and manipulation of quantum states of light is steadily increasing, driven by the need for compact and scalable platforms for quantum information technologies. While photonic circuits with diverse functionalities are being developed in different single material platforms, it has become crucial to realize hybrid photonic circuits that harness the advantages of multiple materials while mitigating their respective weaknesses, resulting in enhanced capabilities. Here, we demonstrate a hybrid III-V/Silicon quantum photonic device combining the strong second-order nonlinearity and direct bandgap of the III-V semiconductor platform with the high maturity and CMOS compatibility of the silicon photonic platform. Our device embeds the spontaneous parametric down-conversion (SPDC) of photon pairs into an AlGaAs source and their vertical routing to an adhesively-bonded silicon-on-insulator circuitry, within an evanescent coupling scheme managing both polarization states. This enables the on-chip generation of broadband (> 40 nm) telecom photons by type 0 and type 2 SPDC from the hybrid device, at room temperature and with internal pair generation rates exceeding $10^5$ $s^{-1}$ for both types, while the pump beam is strongly rejected. Two-photon interference with 92% visibility (and up to 99% upon 5 nm spectral filtering) proves the high energy-time entanglement quality of the produced quantum state, thereby enabling a wide range of quantum information applications on-chip, within an hybrid architecture compliant with electrical pumping and merging the assets of two mature and highly complementary platforms in view of out-of-the-lab deployment of quantum technologies. △ Less

Submitted 23 January, 2026; v1 submitted 21 November, 2023; originally announced November 2023.

Journal ref: PRX Quantum 5, 040321 (2024)

Elliptical micropillars for efficient generation and detection of coherent acoustic phonons

Authors: Chushuang Xiang, Anne Rodriguez, Edson Rafael Cardozo de Oliveira, Luc Le Gratiet, Isabelle Sagnes, Martina Morassi, Aristide Lemaitre, Norberto Daniel Lanzillotti-Kimura

Abstract: Coherent acoustic phonon generation and detection assisted by optical resonances are at the core of efficient optophononic transduction processes. However, when dealing with a single optical resonance, the optimum generation and detection conditions take place at different laser wavelengths, i.e. different detunings from the cavity mode. In this work, we theoretically propose and experimentally de… ▽ More Coherent acoustic phonon generation and detection assisted by optical resonances are at the core of efficient optophononic transduction processes. However, when dealing with a single optical resonance, the optimum generation and detection conditions take place at different laser wavelengths, i.e. different detunings from the cavity mode. In this work, we theoretically propose and experimentally demonstrate the use of elliptical micropillars to reach these conditions simultaneously at a single wavelength. Elliptical micropillar optophononic resonators present two optical modes with orthogonal polarizations at different wavelengths. By employing a cross-polarized scheme pump-probe experiment, we exploit the mode splitting and couple the pump beam to one mode while the probe is detuned from the other one. In this way, at a particular micropillar ellipticity, both phonon generation and detection processes are enhanced. We report an enhancement of a factor of ~3.1 when comparing the signals from elliptical and circular micropillars. Our findings constitute a step forward in tailoring the light-matter interaction for more efficient ultrahigh-frequency optophononic devices. △ Less

Submitted 23 October, 2023; originally announced October 2023.

Comments: 10 pages, 5 figures

Whispering gallery quantum well exciton polaritons in an Indium Gallium Arsenide microdisk cavity

Authors: Romain de Oliveira, Martin Colombano, Florent Malabat, Martina Morassi, Aristide Lemaître, Ivan Favero

Abstract: Despite appealing high-symmetry properties that enable high quality factor and strong confinement, whispering gallery modes of spherical and circular resonators have been absent from the field of quantum-well exciton polaritons. Here we observe whispering gallery exciton polaritons in a Gallium Arsenide microdisk cavity filled with Indium Gallium Arsenide quantum wells, the testbed materials of po… ▽ More Despite appealing high-symmetry properties that enable high quality factor and strong confinement, whispering gallery modes of spherical and circular resonators have been absent from the field of quantum-well exciton polaritons. Here we observe whispering gallery exciton polaritons in a Gallium Arsenide microdisk cavity filled with Indium Gallium Arsenide quantum wells, the testbed materials of polaritonics. Strong coupling is evidenced in photoluminescence and resonant spectroscopy, accessed through concomitant confocal microscopy and near-field optical techniques. Excitonic and optical resonances are tuned by varying temperature and disk radius, revealing Rabi splittings between 5 and 10 meV. A dedicated analytical quantum model for such circular polaritons is developed, which reproduces the measured values. At high power, lasing is observed and accompanied by a blueshift of the emission that points to the regime of polariton lasing. △ Less

Submitted 22 September, 2023; originally announced September 2023.

Bogoliubov excitations driven by thermal lattice phonons in a quantum fluid of light

Authors: Irénée Frérot, Amit Vashisht, Martina Morassi, Aristide Lemaître, Sylvain Ravets, Jacqueline Bloch, Anna Minguzzi, Maxime Richard

Abstract: The elementary excitations in weakly interacting quantum fluids have a non-trivial nature which is at the basis of defining quantum phenomena such as superfluidity. These excitations and the physics they lead to have been explored in closed quantum systems at thermal equilibrium both theoretically within the celebrated Bogoliubov framework, and experimentally in quantum fluids of ultracold atoms.… ▽ More The elementary excitations in weakly interacting quantum fluids have a non-trivial nature which is at the basis of defining quantum phenomena such as superfluidity. These excitations and the physics they lead to have been explored in closed quantum systems at thermal equilibrium both theoretically within the celebrated Bogoliubov framework, and experimentally in quantum fluids of ultracold atoms. Over the past decade, the relevance of Bogoliubov excitations has become essential to understand quantum fluids of interacting photons. Their driven-dissipative character leads to distinct properties with respect to their equilibrium counterparts. For instance, the condensate coupling to the photonic vacuum environment leads to a non-zero generation rate of elementary excitations with many striking implications. In this work, considering that quantum fluids of light are often hosted in solid-state systems, we show within a joint theory-experiment analysis that the vibrations of the crystal constitute another environment that the condensate is fundamentally coupled to. This coupling leads to a unique heat transfer mechanism, resulting in a large generation rate of elementary excitations in typical experimental conditions, and to a fundamental non-zero contribution at vanishing temperatures. Our work provides a complete framework for solid-embedded quantum fluids of light, which is invaluable in view of achieving a regime dominated by photon vacuum fluctuations. △ Less

Submitted 16 April, 2024; v1 submitted 17 April, 2023; originally announced April 2023.

Comments: Main text: 24 pages 6 figures, Supplementary Information : 4 pages, 3 figures

Journal ref: Phys. Rev. X 13, 041058 (2023)

Spin-momentum locking and ultrafast spin-charge conversion in ultrathin epitaxial Bi$_{1-x}$Sb$_x$ topological insulator

Authors: E. Rongione, L. Baringthon, D. She, G. Patriarche, R. Lebrun, A. Lemaitre, M. Morassi, N. Reyren, M. Micica, J. Mangeney, J. Tignon, F. Bertran, S. Dhillon, P. Le Fevre, H. Jaffres, J. -M. George

Abstract: The helicity of 3D topological insulator surface states has drawn significant attention in spintronics owing to spin-momentum locking where the carriers' spin is oriented perpendicular to their momentum. This property can provide an efficient method to convert charge currents into spin currents, and vice-versa, through the Rashba-Edelstein effect. However, experimental signatures of these surface… ▽ More The helicity of 3D topological insulator surface states has drawn significant attention in spintronics owing to spin-momentum locking where the carriers' spin is oriented perpendicular to their momentum. This property can provide an efficient method to convert charge currents into spin currents, and vice-versa, through the Rashba-Edelstein effect. However, experimental signatures of these surface states to the spin-charge conversion are extremely difficult to disentangle from bulk state contributions. Here, we combine spin- and angle-resolved photo-emission spectroscopy, and time-resolved THz emission spectroscopy to categorically demonstrate that spin-charge conversion arises mainly from the surface state in Bi$_{1-x}$Sb$_x$ ultrathin films, down to few nanometers where confinement effects emerge. We correlate this large conversion efficiency, typically at the level of the bulk spin Hall effect from heavy metals, to the complex Fermi surface obtained from theoretical calculations of the inverse Rashba-Edelstein response. %We demonstrate this for film thickness down to a few nanometers, Both surface state robustness and sizeable conversion efficiency in epitaxial Bi$_{1-x}$Sb$_x$ thin films bring new perspectives for ultra-low power magnetic random-access memories and broadband THz generation. △ Less

Submitted 25 March, 2023; originally announced March 2023.

Comments: 23 pages, 3 figures

Probing many-body correlations using quantum-cascade correlation spectroscopy

Authors: Lorenzo Scarpelli, Cyril Elouard, Mattias Johnsson, Martina Morassi, Aristide Lemaitre, Iacopo Carusotto, Jacqueline Bloch, Sylvain Ravets, Maxime Richard, Thomas Volz

Abstract: The radiative quantum cascade, i.e. the consecutive emission of photons from a ladder of energy levels, is of fundamental importance in quantum optics. For example, the two-photon cascaded emission from calcium atoms was used in pioneering experiments to test Bell inequalities. In solid-state quantum optics, the radiative biexciton-exciton cascade has proven useful to generate entangled-photon pai… ▽ More The radiative quantum cascade, i.e. the consecutive emission of photons from a ladder of energy levels, is of fundamental importance in quantum optics. For example, the two-photon cascaded emission from calcium atoms was used in pioneering experiments to test Bell inequalities. In solid-state quantum optics, the radiative biexciton-exciton cascade has proven useful to generate entangled-photon pairs. More recently, correlations and entanglement of microwave photons emitted from a two-photon cascaded process were measured using superconducting circuits. All these experiments rely on the highly non-linear nature of the underlying energy ladder, enabling direct excitation and probing of specific single-photon transitions. Here, we use exciton polaritons to explore the cascaded emission of photons in the regime where individual transitions of the ladder are not resolved, a regime that has not been addressed so far. We excite a polariton quantum cascade by off-resonant laser excitation and probe the emitted luminescence using a combination of spectral filtering and correlation spectroscopy. Remarkably, the measured photon-photon correlations exhibit a strong dependence on the polariton energy, and therefore on the underlying polaritonic interaction strength, with clear signatures from two- and three-body Feshbach resonances. Our experiment establishes photon-cascade correlation spectroscopy as a highly sensitive tool to provide valuable information about the underlying quantum properties of novel semiconductor materials and we predict its usefulness in view of studying many-body quantum phenomena. △ Less

Submitted 18 December, 2022; originally announced December 2022.

Brillouin Scattering Selection Rules in Polarization-Sensitive Photonic Resonators

Authors: Anne Rodriguez, Priya Priya, Edson Cardozo de Oliveira, Luc Le Gratiet, Isabelle Sagnes, Martina Morassi, Aristide Lemaître, Florian Pastier, Loïc Lanco, Martin Esmann, Norberto Daniel Lanzillotti-Kimura

Abstract: The selection rules governing spontaneous Brillouin scattering in crystalline solids are usually taken as intrinsic material properties, locking the relative polarization of excitation and signal in bulk. In this work, we independently manipulate these polarization states by means of optical resonances in elliptical micropillars and demonstrate a polarization-based filtering scheme for Brillouin s… ▽ More The selection rules governing spontaneous Brillouin scattering in crystalline solids are usually taken as intrinsic material properties, locking the relative polarization of excitation and signal in bulk. In this work, we independently manipulate these polarization states by means of optical resonances in elliptical micropillars and demonstrate a polarization-based filtering scheme for Brillouin spectroscopy in the 20-100 GHz range, important for telecom applications. This strong modification of selection rules using elliptical micropillars can be extended to any optical system with localized, polarization-sensitive modes, such as plasmonic resonators, photonic crystals, birefringent micro-, and nanostructures. Our polarization control protocol will thus find applications in the engineering of light-matter interactions in optomechanical, optoelectronic and quantum optics devices. △ Less

Submitted 26 September, 2022; originally announced September 2022.

Comments: 13 pages, 4 figures

Journal ref: ACS Photonics 10, 1687 (2023)

Probing the dynamics and coherence of a semiconductor hole spin via acoustic phonon-assisted excitation

Authors: N. Coste, M. Gundin, D. Fioretto, S. E. Thomas, C. Millet, E. Medhi, M. Gundin, N. Somaschi, M. Morassi, M. Pont, A. Lemaitre, N. Belabas, O. Krebs, L. Lanco, P. Senellart

Abstract: Spins in semiconductor quantum dots are promising local quantum memories to generate polarization-encoded photonic cluster states, as proposed in the pioneering Rudolph-Lindner scheme [1]. However, harnessing the polarization degree of freedom of the optical transitions is hindered by resonant excitation schemes that are widely used to obtain high photon indistinguishability. Here we show that aco… ▽ More Spins in semiconductor quantum dots are promising local quantum memories to generate polarization-encoded photonic cluster states, as proposed in the pioneering Rudolph-Lindner scheme [1]. However, harnessing the polarization degree of freedom of the optical transitions is hindered by resonant excitation schemes that are widely used to obtain high photon indistinguishability. Here we show that acoustic phonon-assisted excitation, a scheme that preserves high indistinguishability, also allows to fully exploit the polarization selective optical transitions to initialise and measure single spin states. We access the coherence of hole spin systems in a low transverse magnetic field and directly monitor the spin Larmor precession both during the radiative emission process of an excited state or in the quantum dot ground state. We report a spin state detection fidelity of $94.7 \pm 0.2 \%$ granted by the optical selection rules and a $20\pm5$~ns hole spin coherence time, demonstrating the potential of this scheme and system to generate linear cluster states with a dozen of photons △ Less

Submitted 13 July, 2022; originally announced July 2022.

Comments: 3 figures

Journal ref: Quantum Sci. Technol. 8 025021 (2023)

A 5.7 THz GaN/AlGaN quantum cascade detector based on polar step quantum wells

Authors: Patrick Quach, Arnaud Jollivet, Andrey Babichev, Nathalie Isac, Martina Morassi, Aristide Lemaitre, Pavel Yunin, Eric Frayssinet, Philippe de Mierry, Mathieu Jeannin, Adel Bousseksou, Raffaele Colombelli, Maria Tchernycheva, Yvon Cordier, François Julien

Abstract: We report on a GaN/AlGaN quantum cascade detector operating in the terahertz spectral range. The device was grown by metal organic chemical vapor deposition on a c-sapphire substrate and relies on polar GaN/AlGaN step quantum wells. The active region thickness is in micrometer range. The structural, electrical and optical investigations attest of high structural quality of the synthetized nitride… ▽ More We report on a GaN/AlGaN quantum cascade detector operating in the terahertz spectral range. The device was grown by metal organic chemical vapor deposition on a c-sapphire substrate and relies on polar GaN/AlGaN step quantum wells. The active region thickness is in micrometer range. The structural, electrical and optical investigations attest of high structural quality of the synthetized nitride material. The detector exhibits a peak photocurrent at 5.7 THz (23.6 meV) with a responsivity of 0.1 mA/W at 10 K under surface normal irradiation through a 10 um period grating. The photocurrent persists up to 20 K. △ Less

Submitted 14 April, 2022; originally announced April 2022.

Observation of KPZ universal scaling in a one-dimensional polariton condensate

Authors: Quentin Fontaine, Davide Squizzato, Florent Baboux, Ivan Amelio, Aristide Lemaître, Marina Morassi, Isabelle Sagnes, Luc Le Gratiet, Abdelmounaim Harouri, Michiel Wouters, Iacopo Carusotto, Alberto Amo, Maxime Richard, Anna Minguzzi, Léonie Canet, Sylvain Ravets, Jacqueline Bloch

Abstract: Revealing universal behaviors is a hallmark of statistical physics. Phenomena such as the stochastic growth of crystalline surfaces, of interfaces in bacterial colonies, and spin transport in quantum magnets all belong to the same universality class, despite the great plurality of physical mechanisms they involve at the microscopic level. This universality stems from a common underlying effective… ▽ More Revealing universal behaviors is a hallmark of statistical physics. Phenomena such as the stochastic growth of crystalline surfaces, of interfaces in bacterial colonies, and spin transport in quantum magnets all belong to the same universality class, despite the great plurality of physical mechanisms they involve at the microscopic level. This universality stems from a common underlying effective dynamics governed by the non-linear stochastic Kardar-Parisi-Zhang (KPZ) equation. Recent theoretical works suggest that this dynamics also emerges in the phase of out-of-equilibrium systems displaying macroscopic spontaneous coherence. Here, we experimentally demonstrate that the evolution of the phase in a driven-dissipative one-dimensional polariton condensate falls in the KPZ universality class. Our demonstration relies on a direct measurement of KPZ space-time scaling laws, combined with a theoretical microscopic analysis that consistently reveals the other key signatures of this universality class, together with the possible resilience of KPZ dynamics to the presence of space-time vortices. Our results highlight fundamental physical differences between out-of-equilibrium condensates and their equilibrium counterparts, and open a new paradigm for exploring universal behaviors in open systems. △ Less

Submitted 28 June, 2022; v1 submitted 17 December, 2021; originally announced December 2021.

Optically defined cavities in driven-dissipative photonic lattices

Authors: O. Jamadi, B. Real, K. Sawicki, C. Hainaut, A. Gonzalez-Tudela, N. Pernet, I. Sagnes, M. Morassi, A. Lemaitre, L. Le Gratiet, A. Harouri, S. Ravets, J. Bloch, A. Amo

Abstract: The engineering of localised modes in photonic structures is one of the main targets of modern photonics. An efficient strategy to design these modes is to use the interplay of constructive and destructive interference in periodic photonic lattices. This mechanism is at the origin of defect modes in photonic bandgaps, bound states in the continuum and compact localised states in flat bands. Here w… ▽ More The engineering of localised modes in photonic structures is one of the main targets of modern photonics. An efficient strategy to design these modes is to use the interplay of constructive and destructive interference in periodic photonic lattices. This mechanism is at the origin of defect modes in photonic bandgaps, bound states in the continuum and compact localised states in flat bands. Here we show that in lattices of lossy resonators, the addition of external optical drives with controlled phase enlarges the possibilities of manipulating interference effects and allows designing novel types of localised modes. Using a honeycomb lattice of coupled micropillars resonantly driven with several laser spots at energies within its photonic bands we demonstrate the localisation of light in at-will geometries down to a single site. These localised modes can be seen as fully reconfigurable optical cavities with the potentiality of enhancing nonlinear effects and of controlling light-matter interactions with single site resolution. △ Less

Submitted 14 December, 2021; originally announced December 2021.

Comments: 15 pages main text + 8 pages supplemental

Topological gap solitons in a 1D non-Hermitian lattice

Authors: N. Pernet, P. St-Jean, D. D. Solnyshkov, G. Malpuech, N. Carlon Zambon, B. Real, O. Jamadi, A. Lemaître, M. Morassi, L. Le Gratiet, T. Baptiste, A. Harouri, I. Sagnes, A. Amo, S. Ravets, J. Bloch

Abstract: Nonlinear topological photonics is an emerging field aiming at extending the fascinating properties of topological states to the realm where interactions between the system constituents cannot be neglected. Interactions can indeed trigger topological phase transitions, induce symmetry protection and robustness properties for the many-body system. Moreover when coupling to the environment via drive… ▽ More Nonlinear topological photonics is an emerging field aiming at extending the fascinating properties of topological states to the realm where interactions between the system constituents cannot be neglected. Interactions can indeed trigger topological phase transitions, induce symmetry protection and robustness properties for the many-body system. Moreover when coupling to the environment via drive and dissipation is also considered, novel collective phenomena are expected to emerge. Here, we report the nonlinear response of a polariton lattice implementing a non-Hermitian version of the Su-Schrieffer-Heeger model. We trigger the formation of solitons in the topological gap of the band structure, and show that these solitons demonstrate robust nonlinear properties with respect to defects, because of the underlying sub-lattice symmetry. Leveraging on the system non-Hermiticity, we engineer the drive phase pattern and unveil bulk solitons that have no counterpart in conservative systems. They are localized on a single sub-lattice with a spatial profile alike a topological edge state. Our results demonstrate a tool to stabilize the nonlinear response of driven dissipative topological systems, which may constitute a powerful resource for nonlinear topological photonics. △ Less

Submitted 4 January, 2021; originally announced January 2021.

Journal ref: Nature Physics 18, 678 (2022)