arXiv subjects

Cesare Soci

Publications and source records attributed to Cesare Soci.

At least 19 recordsLinked to original sources

arXiv2026

Single-photon polarization tomography with an integrated metal-superconductor nanowire array

Light polarization is a primary degree of freedom for encoding quantum information. The scaling up of photonic quantum networks and computer architecture depends crucially on its precise characterization. This is typically achieved by placing external waveplates, polarizers, moving mounts, and recently metasurfaces, on top of the detectors. All these solutions complicate integration and scaling. Here we break convention with traditional architecture and present a monolithic, self-aligned metal-superconductor nanowire single photon detector (M-SNSPD) possessing intrinsic full polarization selectivity. Gold nanowires, co-fabricated atop NbTiN superconducting nanowires within the same lithographic footprint, act as polarization-selective plasmonic metamaterials inducing resonant absorption in the NbTiN. U-shaped wires provide linear polarization selectivity, while S-shaped meanders distinguish circular polarization, while retaining the high-count rates and low dark count rates of conventional SNSPDs. By arranging them into a four-pixel array we realize simultaneous projection onto four polarizations and demonstrate continuous polarization state tomography with an ensemble average fidelity exceeding 98%. Our approach opens new avenues towards scalable detector arrays with integrated plasmonic functionalities, for single photon polarimetry, imaging and spectroscopy.

physics.optics↗

arXiv2026

Topology-guided vortices in a polariton condensate

A major challenge in polariton fluids is achieving deterministic control over the spin texture of the macroscopic condensate wavefunction, which dictates the nucleation and dynamics of topological excitations, such as vortices, solitons, and strings. Existing approaches typically rely on external gauge fields to indirectly access the polariton pseudospin, resulting in configurations that are weakly constrained by the cavity modes and therefore highly sensitive to disorder and fluctuations. Here, we report the generation of spin polaritons constrained to the topology of a bound state in the continuum (BIC) metasurface with broken inversion symmetry carved into a polycrystalline halide-perovskite film. Geometry-induced polariton condensation under spin-momentum locking gives rise to a pair of half-vortices of opposite spin, intrinsically pinned to polarization strings, emerging as topological extensions of the vortex cores. Consequently, varying the excitation density drives a controlled displacement of the half-vortices along the trajectories imposed by the strings, hindering their mutual annihilation across an interposed topological domain wall. This approach establishes cavity geometry as an intrinsic source of spin textures to guide vortex displacement in driven quantum fluids, opening a route toward the generation of robust topological excitations within structurally disordered materials.

physics.app-ph↗

arXiv2026

Gouy phase-assisted Zeno effect for protecting light structure in random media

Identifying physical mechanisms that protect the information carried by various forms of structured light is one of the cornerstones of today's classical and quantum communications. Here we show that the purity of orbital angular momentum (OAM) modes can be protected against degradation in random media by leveraging two fundamental features of their own Schrödinger Hamiltonian dynamics, namely, Zeno effect -- frequent observations slow down the evolution -- , and Gouy phase -- the back-action of the observation. Repeated, OAM-dependent Gouy phase kicks imparted along the disturbing path by simple imaging systems trigger the optical Zeno effect that protects the input OAM mode against mode cross-talk that would broaden the OAM spectrum. Given the universality of the mechanism, the Gouy phase-assisted Zeno effect would protect propagation modes other than those of OAM, and the diverse forms of structured light built with them.

physics.optics↗

arXiv2025

Inline Quantum Measurements with SNSPDs Coupled to Photonic Bound States

We report the realization of inline quantum measurements with waveguide-integrated superconducting nanowire single-photon detectors (SNSPDs). To suppress parasitic scattering at detector terminations, while ensuring compatibility with standard photonic substrates and cryogenic operation, we developed a photonic bound states in the continuum (BIC) platform based on etchless polymer waveguides. We show BIC-coupled inline detectors with on-chip efficiency exceeding 80%, recovery time of less than 2 ns, and intrinsic jitter of less than 70 ps. As a proof of principle, we implement Hanbury Brown and Twiss interferometry and photon number resolution with two collinear detectors within a footprint of $60 \cdot 6$ $μm^2$. The concept of inline quantum measurements could be further developed to support more complex circuit functionalities, such as higher-order correlation measurements, quantum state tomography, and multi-photon subtraction, within a compact architecture.

quant-ph↗

arXiv2025

Anti-Hong-Ou-Mandel interference by coherent perfect absorption of entangled photons

Two-photon interference, known as the Hong-Ou-Mandel effect, has colossal implications for quantum technology. It was observed in 1987 with two photodetectors monitoring outputs of the beamsplitter illuminated by photon pairs: the coincidence rate of the detectors drops to zero when detected photons overlap in time. More broadly, bosons (e.g., photons) coalesce while fermions (e.g., electrons) anti-coalesce when interfering on a lossless beamsplitter. Quantum interference of bosons and fermions can be tested in a single - photonics platform, where bosonic and fermionic states are artificially created as pairs of entangled photons with symmetric and anti-symmetric spatial wavefunctions. We observed that interference on a lossy beamsplitter, or a subwavelength coherent absorber reverses quantum interference in such a way that bosonic states anti-coalesce while fermionic states exhibit coalescent-like behavior. The ability to generate states of light with different statistics and manipulate their interference offers important opportunities for quantum information and metrology.

quant-ph↗

arXiv2025

Beyond the Dicke Limit: Superradiant J-Exciton-Polaritons in BIC Metasurfaces

Highly correlated photon sources can be realized through cooperative coupling among quantum systems, giving rise to superradiant collective emission. In solid-state ensembles, however, such collective behaviour is typically confined to subwavelength dimensions (the Dicke limit) and strongly suppressed at room temperature by inhomogeneous broadening and rapid dephasing, hindering practical implementations. Here, we show that molecular J-aggregates sustain room temperature superradiant emission and enter a highly collective regime when strongly coupled to the delocalized photonic modes of a silicon bound-state-in-the-continuum (BIC) metasurface. J-exciton polaritons exhibit markedly enhanced, excitation-density-dependent cooperativity, evidenced by an increase in the zero-delay second-order correlation to g^((2))(0)=3.77, well within the superbunched emission regime (g^((2))(0)>2), and by the growth and reorganization of spatially synchronized emissive domains over areas as large as 8.5 um^2, far exceeding the characteristic Dicke area ({\lambda}^2) at the emission wavelength of 589 nm. An interacting-emitter model identifies superradiant clustering as the mechanism by which metasurface-mediated interactions extend J-exciton cooperativity, establishing resonant dielectric metasurfaces as a route towards micrometre-scale superradiance and enhanced photon correlations in disordered materials.

physics.app-ph↗

arXiv2025

Fourier State Tomography of Polarization-Encoded Qubits

Quantum state tomography is a central technique for the characterization and verification of quantum systems. Standard tomography is widely used for low-dimensional systems, but for larger systems, it becomes impractical due to the exponential scaling of experimental complexity with the number of qubits. Here, we present an experimental realization of Fourier-transform quantum state tomography for polarization-encoded photonic states. We validate the technique using weak coherent states and entangled photon pairs generated by a quantum dot and spontaneous parametric down-conversion source in the telecom wavelength. The reconstructed density matrices show excellent agreement with those obtained through conventional projective tomography, with calculated metrics such as fidelity and concurrence matching within error bars, confirming the reliability and accuracy of the technique. Fourier state tomography employs only a single rotating waveplate per qubit, thereby avoiding repeated adjustments across multiple waveplates and ensuring that the number of physical measurement settings scales linearly with the number of qubits, despite the exponential growth of the underlying state space. This reduction in optical configurations simplifies experimental overhead, making Fourier state tomography a practical alternative for multi-qubit characterization.

quant-ph↗

arXiv2025

Enhanced quantum magnetometry with a laser-written integrated photonic diamond chip

An ensemble of negatively charged nitrogen-vacancy centers in diamond can act as a precise quantum sensor even under ambient conditions. In particular, to optimize thier sensitivity, it is crucial to increase the number of spins sampled and maximize their coupling to the detection system, without degrading their spin properties. In this paper, we demonstrate enhanced quantum magnetometry via a high-quality buried laser-written waveguide in diamond with a 4.5 ppm density of nitrogen-vacancy centers. We show that the waveguide-coupled nitrogen-vacancy centers exhibit comparable spin coherence properties as that of nitrogen-vacancy centers in pristine diamond using time-domain optically detected magnetic resonance spectroscopy. Waveguide-enhanced magnetic field sensing is demonstrated in a fiber-coupled integrated photonic chip, where probing an increased volume of high-density spins results in 63 pT$.$Hz $^{-1/2}$ of DC-magnetic field sensitivity and 20 pT$.$Hz $^{-1/2}$ of AC magnetic field sensitivity. This on-chip sensor realizes at least an order of magnitude improvement in sensitivity compared to the conventional confocal detection setup, paving the way for microscale sensing with nitrogen-vacancy ensembles.

quant-ph↗

arXiv2024

Wavelength Control of Perovskite Metasurface Lasing via Electrical Microheaters

Perovskites have recently brought significant advances to active nanophotonics, offering a unique combination of gain and phase-change properties for tunable light-emitting devices. However, current wavelength-tunable devices often rely on tuning mechanisms or device architectures that lead to slow modulation or bulky setups. In this study, we overcome limitations on speed and size by demonstrating a compact tunable microlaser embedding electrical microheaters beneath a perovskite metasurface. This architecture allows to efficiently deliver heat and rapidly modulate the phase transition. Our device leverages the optical gain and crystallographic phase tuning of the perovskite, and a high-quality factor cavity design based on bound states in the continuum. With it, we demonstrate reversible laser wavelength switching between 763 nm and 783 nm within 13 ms at 2.3 V. This work unlocks the potential of perovskite metasurfaces for electrically tunable light sources and introduces a flexible platform which can be easily extended to the dynamic control of polarization or directionality for optical communication, sensing and spectroscopy.

physics.optics↗

arXiv2024

Nonlinear interferometry-based metrology of magneto-optical properties at infrared wavelengths

Magneto-optical properties of materials are utilized in numerous applications both in scientific research and industries. The novel properties of these materials can be further investigated by performing metrology in the infrared wavelength range, thereby enriching their potential applications. However, current infrared metrology techniques can be challenging and resource-intensive due to the unavailability of suitable components. To address these challenges, we propose and demonstrate a set of measurements based on nonlinear interferometry, which allows us investigating magneto-optical properties of materials at infrared wavelength range by performing optical detection at the visible range. For a proof-of-principle study, we measure the Verdet constant of a bismuth-iron-garnet, over a spectral bandwidth of 600 nm in the near-IR range.

physics.optics↗

arXiv2024

Electrically generated exciton polaritons with spin on-demand

Generation and manipulation of exciton polaritons with controllable spin could deeply impact spintronic applications, quantum simulations, and quantum information processing, but is inherently challenging due to the charge neutrality of the polariton and the device complexity it requires. In this work, we demonstrate electrical generation of spin-polarized exciton polaritons in a monolithic dielectric perovskite metasurface embedded in a light-emitting transistor. A finely tailored interplay of in- and out-of-plane symmetry breaking of the metasurface allows to lift the spin degeneracy through the polaritonic Rashba effect, yielding high spin purity with normalized Stokes parameter of S3~0.8. Leveraging on spin-momentum locking, the unique metatransistor device architecture enables electrical control of spin and directionality of the polaritonic emission. This work advances the development of compact and tunable spintronic devices, and represents an important step toward the realization of electrically pumped inversionless spin-lasers.

physics.optics↗

arXiv2024

Dirac mass induced by optical gain and loss

Mass is commonly regarded as an intrinsic property of matter, but modern physics reveals particle masses to have complex origins, such as the Higgs mechanism in high-energy physics. In crystal lattices such as graphene, relativistic Dirac particles can exist as low-energy quasiparticles with masses imparted by lattice symmetry-breaking perturbations. These mass-generating mechanisms all assume Hermiticity, or the conservation of energy in detail. Using a photonic synthetic lattice, we show experimentally that Dirac masses can be generated via non-Hermitian perturbations based on optical gain and loss. We then explore how the space-time engineering of the gain/loss-induced Dirac mass affects the quasiparticles. As we show, the quasiparticles undergo Klein tunnelling at spatial boundaries, but a local breaking of a non-Hermitian symmetry can produce a novel flux nonconservation effect at the domain walls. At a temporal boundary that abruptly flips the sign of the Dirac mass, we observe a variant of the time reflection phenomenon: in the nonrelativistic limit, the Dirac quasiparticle reverses its velocity, while in the relativistic limit the original velocity is retained.

cond-mat.mes-hall↗

arXiv2023

Asynchronous Charge Carrier Injection in Perovskite Light-Emitting Transistors

Unbalanced mobility and injection of charge carriers in metal-halide perovskite light-emitting devices pose severe limitations to the efficiency and response time of the electroluminescence. Modulation of gate bias in methylammonium lead iodide light-emitting transistors has proven effective to increase the brightness of light emission, up to MHz frequencies. In this work, we developed a new approach to improve charge carrier injection and enhance electroluminescence of perovskite light-emitting transistors by independent control of drain-source and gate-source bias voltages to compensate for space-charge effects. Optimization of bias pulse synchronization induces a fourfold enhancement of the emission intensity. Interestingly, the optimal phase delay between biasing pulses depends on modulation frequency due to the capacitive nature of the devices, which is well captured by numerical simulations of an equivalent electrical circuit. These results provide new insights into the electroluminescence dynamics of AC-driven perovskite light-emitting transistors and demonstrate an effective strategy to optimize device performance through independent control of amplitude, frequency, and phase of the biasing pulses.

physics.app-ph↗

arXiv2023

Topological Insulator Metamaterials

Confinement of electromagnetic fields at the subwavelength scale via metamaterial paradigms is an established method to engineer light-matter interaction in most common material systems, from insulators to semiconductors, from metals to superconductors. In recent years, this approach has been extended to the realm of topological materials, providing a new avenue to access nontrivial features of their electronic band structure. In this review, we survey various topological material classes from a photonics standpoint, including crystal growth and lithographic structuring methods. We discuss how exotic electronic features such as spin-selective Dirac plasmon polaritons in topological insulators or hyperbolic plasmon polaritons in Weyl semimetals may give rise to unconventional magneto-optic, non-linear and circular photogalvanic effects in metamaterials across the visible to infrared spectrum. Finally, we dwell on how these effects may be dynamically controlled by applying external perturbations in the form of electric and magnetic fields or ultrafast optical pulses. Through these examples and future perspectives, we argue that topological insulator, semimetal and superconductor metamaterials are unique systems to bridge the missing links between nanophotonic, electronic and spintronic technologies.

physics.optics↗

arXiv2022

Photon number resolution without optical mode multiplication

Common methods to achieve photon number resolution rely on fast on-off single-photon detectors in conjunction with temporal or spatial mode multiplexing. Yet, these methods suffer from an inherent trade-off between the efficiency of photon number discrimination and photon detection rate. Here, we introduce a method of photon number resolving detection that overcomes these limitations by replacing mode multiplexing with coherent absorption of a single optical mode in a distributed detector array. Distributed coherent absorption ensures complete and uniform absorption of light among the constituent detectors, enabling fast and efficient photon number resolution. As a proof-of-concept, we consider the case of a distributed array of superconducting nanowire single-photon detectors with realistic parameters and show that deterministic absorption and arbitrarily high photon number discrimination efficiency can be achieved by increasing the number of detectors in the array. Photon number resolution without optical mode multiplication provides a simple yet effective method to discriminate an arbitrary number of photons in large arrays of on-off detectors or in smaller arrays of mode multiplexed detectors.

quant-ph↗

arXiv2022

Electrically driven exciton-polaritons in metal halide perovskite metatransistors

Achieving electrical injection of exciton-polaritons, half-light, half-matter quasiparticles arising from the strong coupling between photonic and excitonic resonances, is a crucial milestone to scale up polaritonic devices such as optical computers, quantum simulators and inversionless lasers. Here we present a new approach to achieve strong coupling between electrically injected excitons and photonic bound states in the continuum of a dielectric metasurface monolithically patterned in the channel of a light-emitting transistor. Exciton-polaritons are generated by coupling electrically injected excitons in the gate-induced transport channel with a Bloch mode of the metasurface, and decay into photons emitted from the top surface of the transistor. Thanks to the high-finesse of the metasurface cavity, we achieve a large Rabi splitting of ~200 meV and more than 50-fold enhancement of the polaritonic emission over the intrinsic excitonic emission of the perovskite film. Moreover, we show that the directionality of polaritonic electroluminescence can be dynamically tuned by varying the source-drain bias which controls the radiative recombination zone of the excitons. We argue that this approach provides a new platform to study strong light-matter interaction in dispersion engineered photonic cavities under electrical injection, and paves the way to solution-processed electrically pumped polariton lasers.

physics.optics↗

arXiv2022

Color-Tunable Mixed-Cation Perovskite Single Photon Emitters

Quantum photonics technologies like wavelength division multiplexing (WDM) for high-rate quantum key distribution require narrowband, spectrally tunable single photon emitters. Physical methods that rely on the application of large mechanical strain to epitaxial quantum dots or electric and magnetic fields to color centers in 2D metal dichalcogenides provide limited spectral tunability. Here we adopt a chemical approach to synthesize a family of colloidal mixed-cation perovskite quantum dots ($\text{Cs}_{1-x}\text{FA}_{x}\text{PbBr}_3$) that show highly photo-stable, compositionally tunable single photon emission at room temperature - spanning more than 30 nm in the visible wavelength spectral range. We find that, tailoring the stoichiometry of the organic formamidinium (FA) cation in all-inorganic cesium lead bromide ($\text{CsPbBr}_3$) perovskite quantum dots detunes the electronic band structure while preserving their excellent single photon emission characteristics. We argue that the mixed-cation perovskite quantum dots studied in this work offer a new platform for the realization of color-tunable single photon emitters that could be readily integrated in a diversity of quantum photonic devices.

quant-ph↗

arXiv2022

Polarization-Tunable Perovskite Light-Emitting Metatransistor

Emerging immersive visual communication technologies require light sources with complex functionality for dynamic control of polarization, directivity, wavefront, spectrum, and intensity of light. Currently, this is mostly achieved by free space bulk optic elements, limiting the adoption of these technologies. Flat optics based on artificially structured metasurfaces that operate at the sub-wavelength scale are a viable solution, however their integration into electrically driven devices remains challenging. Here we demonstrate a radically new approach of monolithic integration of a dielectric metasurface into a perovskite light-emitting transistor. We show that nanogratings directly structured on top of the transistor channel yield an 8-fold increase of electroluminescence intensity and dynamic tunability of polarization. This new light-emitting metatransistor device concept opens unlimited opportunities for light management strategies based on metasurface design and integration.

physics.optics↗