arXiv subjects

Haim Suchowski

Publications and source records attributed to Haim Suchowski.

At least 19 recordsLinked to original sources

arXiv2026

End-to-End Quantum Key Distribution Across Hybrid Fiber and Free-Space Links with All-Optical Encoding Conversion

Quantum key distribution (QKD) promises information-theoretically secure communication, but future networks must bridge fiber and free-space links that naturally employ different photonic encodings, namely time-bin in fiber and polarization in free space. Here we demonstrate a complete hybrid fiber and free-space QKD link that bridges both media within a single end-to-end protocol, converting between the two encodings entirely in the optical domain. Using the decoy-state BB84 protocol operating at 1550 nm, we demonstrate continuous secure-key generation over a 90 m outdoor free-space link. The system operates across atmospheric conditions spanning more than two orders of magnitude in the refractive-index structure parameter Cn^2, from strong daytime turbulence to quiescent nighttime conditions, and we further validate photon-level operation over a 750 m free-space extension. Throughout, the link maintains a session-mean quantum bit error rate (QBER) of 5.6-6.8%, well below the 11% BB84 security threshold. The encoding conversion is performed entirely in the optical domain without measurement or state reconstruction, preserving the security assumptions of the BB84 protocol. Consequently, the time-bin-to-polarization (T2P) and polarization-to-time-bin (P2T) converters remain part of the untrusted quantum channel rather than trusted intermediate nodes. These results establish secure photonic encoding conversion as a practical interface between fiber and free-space quantum communication platforms, providing a building block for future quantum networks applications.

quant-ph↗

arXiv2026

High Frame-Rate Mid-Infrared SPAD Camera

Single-photon avalanche diode (SPAD) arrays have transformed optical imaging by enabling photon-counting sensitivity, picosecond resolution, and high frame-rate operation. These capabilities, however, have remained confined to the visible and near-infrared, leaving the mid-infrared, the spectral region hosting the fundamental vibrational signatures of most molecules, largely inaccessible. Here, we demonstrate the first mid-IR SPAD camera by integrating broadband adiabatic frequency upconversion with a 512x512 Silicon SPAD array. This architecture transfers full SPAD functionality to the mid-IR, enabling room-temperature, low-noise, broadband photon-counting imaging. We achieve spectrally resolved mid-IR imaging at frame rates of up to 60,000 frames per second and capture nanosecond-scale laser-induced thermal dynamics via weak mid-IR blackbody emission, revealing spatial-temporal behavior inaccessible to existing technologies. These results establish a scalable platform for photon-resolved, ultrafast thermal and chemical imaging in a spectral range previously inaccessible to high-speed low-light detection.

physics.optics↗

arXiv2026

Polytype-Dependent Upconversion Photoluminescence in 3R-MoS2

Ferroelectric van der Waals materials offer switchable polarization states, yet optical readout of their stacking configurations remains challenging. Here, building on the resonant exciton-exciton annihilation (EEA) mechanism recently identified in 2H-phase TMDs, we report the first observation of upconversion photoluminescence (UPL) in rhombohedral MoS$_2$ and demonstrate that this many-body process is strongly polytype-dependent. Using low-temperature spectroscopy, we observe anti-Stokes emission with superlinear power dependence characteristic of EEA. Beyond serving as an accurate layer-number sensor due to discrete bandgap variations, UPL provides a sensitive probe of stacking order across thicknesses. The two neutral trilayer polytypes, which remain indistinguishable by surface potential measurements and second harmonic generation, exhibit markedly different UPL intensities. This sensitivity persists in thicker samples where multiple configurations coexist. First-principles calculations suggest that the intensity contrast originates primarily from the layer confinement of the annihilating excitons, while energy matching to the $\Gamma$ final-state manifold provides additional intensity selectivity. Power-dependent spectroscopy further disentangles two distinct annihilation channels originating from different dark exciton valleys, identified through their contrasting intensity scaling and opposite density-induced energy shifts. Crucially, the annihilation process doubles the energy separation of nearly degenerate dark excitons while converting their weak emission into bright signal, providing experimental access to valley-specific responses that are obscured in direct dark-exciton spectroscopy. Our findings demonstrate that ferroelectric configurations provide a new degree of freedom for controlling nonlinear optical processes.

cond-mat.mtrl-sci↗

arXiv2026

Single-Shot Multispectral Mid-Infrared Imaging with Incoherent Light via Adiabatic Upconversion

Multispectral mid-infrared (2-5 ${{\mu}m}$) imaging is a critical capability across science and technology, offering a window into the vibrational and thermal landscape of matter that is inaccessible to visible sensors. It bridges the microscopic world of molecular interactions with macroscopic sensing technologies, with applications in environmental sensing, defense and molecular diagnostics. However, current mid-IR cameras require cryogenic cooling and exhibit limited pixel resolution, high cost, and restricted spectral access. Optical up-conversion provides a pathway to overcome these limitations, but existing systems typically rely on narrowband phase matching, mechanical scanning, or angular tuning, limiting imaging speed and practicality. Here, we demonstrate the first single-shot, room-temperature multispectral mid-IR imaging of incoherent thermal light enabled by adiabatic sum-frequency conversion. Our system simultaneously converts the entire (2-5 ${{\mu}m}$) region into the visible domain, capturing the image on a Silicon detector with spatial resolution below 20 ${{\mu}m}$ and high angular tolerance. We validate full-field imaging using a USAF resolution target and demonstrate spectroscopic contrast imaging in dielectric metamaterials by resolving wavelength and polarization dependent scattering resonances, all achieved without scanning, thermal control, or cryogenic operation. This compact and robust approach bridges the gap between laboratory-grade infrared sensors and scalable Silicon-based detection technologies suitable for real-world deployment.

physics.optics↗

arXiv2025

Pre-Distillation of Magic States via Composite Schemes

Magic state distillation (MSD) is a cornerstone of fault-tolerant quantum computing, enabling non-Clifford gates via state injection into stabilizer circuits. However, the substantial overhead of current MSD protocols remains a major obstacle to scalable implementations. We propose a general framework for pre-distillation, based on composite pulse sequences that suppress systematic errors in the generation of magic states. While most composite designs target simple gates such as X, Z, or Hadamard, our schemes directly implement the non-Clifford T gate with enhanced robustness to the targeted systematic errors. We develop composite sequences tailored to the dominant control imperfections in superconducting, trapped-ion, neutral-atom, and integrated photonic platforms. To quantify improvement in the implementation, we introduce an operationally motivated fidelity measure specifically tailored to the T gate: the T-magic error, which captures the gate's effectiveness in preparing high-fidelity magic states. We further show that the error in the channel arising from the injection of faulty magic states scales linearly with the leading-order error of the states. Within the systematic-error-dominated regimes considered, this approach lowers the number of required distillation levels by up to three across the platforms we study, translating to substantial qubit-overhead savings and offering a practical route toward more resource-efficient universal quantum computation.

quant-ph↗

arXiv2025

High fidelity CNOT gates in photonic integrated circuits using composite segmented directional couplers

Integrated photonic circuits are a promising platform for scalable quantum information processing, but their performance is often constrained by component sensitivity to fabrication imperfections. Directional couplers, which are crucial building blocks for integrated quantum logic gates, are particularly prone to such limitations, with strong dependence on geometric and spectral parameters which reduces gate fidelity. Here, we demonstrate that composite segmented directional couplers (CSDC) offer a fabrication-tolerant alternative that enhances gate fidelity without active tuning. We design and fabricate a fully integrated photonic controlled-NOT (CNOT) gate using both uniform and composite coupler variants and compare their performance via simulation, classical characterization, and quantum two-photon interference. The composite design reduces the average error probability by nearly a factor of two and decreases variability fivefold. The residual error is primarily limited by photon indistinguishability. Classical matrix reconstruction confirms improved agreement with the ideal CNOT operation. These results establish CSDCs as compact, passive, and foundry-compatible building blocks for robust scalable quantum photonic circuits.

physics.optics↗

arXiv2025

Shaping Ultrafast Pulses for Enhanced Resonant Nonlinear Interactions

Coherent control with shaped ultrafast pulses is a powerful approach for steering nonlinear light-matter interactions. Previous studies in quantum control have shown that, beyond transform-limited pulses, those with antisymmetric spectral phases can drive nonresonant multiphoton transitions with comparable efficiency. However, in resonant multiphoton transitions, the material's spectral-phase response introduces dispersion that degrades nonlinear efficiency. Pre-shaping the pulse to compensate for the material's impulse response can restore and enhance nonlinear interactions beyond the transform-limited case. Yet, is this the only spectral phase that can yield such enhancement? Here, we study sub-10 fs single-pulse four-wave mixing in resonant plasmonic nanostructures using arctangent spectral-phase-shaped pulses. We uncover two distinct enhancement regimes: one compensating for material dispersion, and a counterintuitive regime where the arctangent phase induces an antisymmetric polarization response, driving constructive multiphoton pathway interference. Our theoretical analysis provides clear physical explanation for both phenomena. Notably, it predicts that both enhancement mechanisms scale exponentially with harmonic order, offering a powerful strategy for dramatically enhancing high-order harmonic generation in resonant systems.

physics.optics↗

arXiv2025

Deep Learning for Optical Misalignment Diagnostics in Multi-Lens Imaging Systems

In the rapidly evolving field of optical engineering, precise alignment of multi-lens imaging systems is critical yet challenging, as even minor misalignments can significantly degrade performance. Traditional alignment methods rely on specialized equipment and are time-consuming processes, highlighting the need for automated and scalable solutions. We present two complementary deep learning-based inverse-design methods for diagnosing misalignments in multi-element lens systems using only optical measurements. First, we use ray-traced spot diagrams to predict five-degree-of-freedom (5-DOF) errors in a 6-lens photographic prime, achieving a mean absolute error of 0.031mm in lateral translation and 0.011$^\circ$ in tilt. We also introduce a physics-based simulation pipeline that utilizes grayscale synthetic camera images, enabling a deep learning model to estimate 4-DOF, decenter and tilt errors in both two- and six-lens multi-lens systems. These results show the potential to reshape manufacturing and quality control in precision imaging.

physics.optics↗

arXiv2025

Time-Domain Excitation of Finite-Lifetime Resonances and Their Exceptional Points

Resonances associated with complex-frequency poles are ubiquitous across physics and can arise in any open system, ranging from subwavelength particles and cavities to biological structures. When two such resonances coalesce, they form exceptional points (EPs), non-Hermitian singularities known to produce unusual spectral and dynamical behavior. However, the dynamics of the response of such resonances and exceptional points to complex frequency drive remained largely unexplored. Here, we experimentally observe the temporal response of complex-frequency resonances and theoretically study this for exceptional points. We unveil a universal transient phenomenon of open cavities driven at complex frequencies: the system's initial response grows linearly, with enhanced growth at exceptional points (EPs), even though the system is passive and the excitation decays. Closed-form theory for general resonators, extended to higher-order modes, predicts efficient power transfer with $t$ and $t^2$ scaling for complex single poles and exceptional points (EPs), respectively, at all times. We demonstrate these effects in subwavelength optical scatterers and experimentally in an electrical circuit analogue, with excellent agreement, and explore configurations that capture EP-enhanced growth.

physics.optics↗

arXiv2025

Photoluminescence Detection of Polytype Polarization in r-MoS2 Enabled by Asymmetric Dielectric Environments

The rhombohedral (r) polytypes of transition metal dichalcogenides (TMDs) constitute a novel class of two-dimensional ferroelectric materials, where lateral shifts between parallel layers induce reversible out-of-plane polarization. This emerging field, known as SlideTronics, holds significant potential for next-generation electronic and optoelectronic applications. While extensive studies have investigated the effects of electrical and chemical doping on excitonic signatures in 2H-TMDs, as well as the influence of dielectric environments on their optical properties, the impact of intrinsic polarization in asymmetric environments remains largely unexplored. Here, we demonstrate a striking polarization-dependent photoluminescence (PL) contrast of up to 400\% between ferroelectric domains in bilayer and trilayer rhombohedral molybdenum disulfide (r-MoS2). This pronounced contrast arises from an asymmetric dielectric environment, which induces polarization-dependent shifts in the Fermi energy, leading to a modulation of the exciton-trion population balance. A detailed temperature-dependent line shape analysis of the PL, conducted from 4K to room temperature, reveals domain-specific trends that further reinforce the connection between polarization states and excitonic properties. The persistence of these distinct optical signatures at room temperature establishes PL as a robust and non-invasive probe for ferroelectric domain characterization, particularly in fully encapsulated device architectures where conventional techniques, such as Kelvin probe force microscopy, become impractical.

cond-mat.mtrl-sci↗

arXiv2025

High-Fidelity Integrated Quantum Photonic Logic Via Robust Directional Couplers

Scalable quantum information processing with integrated photonics requires quantum logic operations with high fidelity and robustness. Directional couplers, the fundamental elements enabling quantum interference and logic operations, are inherently sensitive to fabrication imperfections and environmental fluctuations, leading to reduced gate fidelities. Here, we experimentally demonstrate a passive design strategy that mitigates these errors by exploiting a stationary geometrical configuration in uniform directional couplers, where first-order variations in the coupling coefficient are intrinsically suppressed. The robust geometry is implemented in a silicon-on-insulator photonic chip hosting two-photon controlled-NOT (CNOT) quantum gates and its performance is directly compared to a non-optimized design. Measurements indicate a mean gate fidelity of $93.30 \pm 0.11\%$, representing a clear improvement over the non-robust implementation mean fidelity of $91.93 \pm 0.17\%$, without any active tuning or footprint increase. This performance approaches the theoretical limit of $93.78\%$, imposed by the imperfect source. Monte Carlo simulations incorporating realistic fabrication noise confirm the observed enhancement and reveal consistent suppression of gate-level error rates. These results demonstrate a compact, fabrication-tolerant building block for scalable, fault-tolerant photonic quantum circuits and highlight the power of passive geometric error mitigation in quantum hardware design.

physics.optics↗

arXiv2025

Accurate Modeling of Directional Couplers with Oxide Cladding: Bridging Simulation and Experiment

Directional couplers are a fundamental building block in integrated photonics, particularly in quantum applications and optimization-based design where precision is critical. Accurate functionality is crucial to ensure reliable operation within classical and quantum circuits. However, discrepancies between simulations and measurements are frequently observed. These inaccuracies can compromise the performance and scalability of integrated photonic systems, underscoring the critical need for advanced, precise simulation methods that bridge the gap between design and implementation. In this work, we show that this discrepancy can be mainly attributed to density changes in the oxide cladding. We conduct a systematic study involving experimental optical measurements, numerical simulations, and direct electron microscopy imaging to investigate this discrepancy in directional couplers. We find that the impact of cladding density variations on performance increases as feature gaps shrink. By incorporating these effects into our simulations using a novel and physically motivated Effective Trench Medium Model (ETMM), we achieve highly accurate reproduction of experimental measurements. We quantify the effects of cladding density variations on the SU(2) symmetry parameters that govern light propagation in directional couplers. This insight is crucial for advancing the precision of compact device fabrication, enabling reliable simulation of photonic integrated devices.

physics.optics↗

arXiv2024

Robust Characterization of Integrated Photonics Directional Couplers

Directional couplers are essential components in integrated photonics. Given their widespread use, accurate characterization of directional couplers is crucial for ensuring optimal performance. However, it is challenging due to the coupling between fibers and waveguides, which is highly sensitive to alignment and fabrication imperfections. To address these challenges, we propose a novel direct measurement technique that offers greater robustness to variations in optical interfaces, while bypassing extinction ratio measurements. Our method enables a broadband and precise characterization of the directional couplers' splitting ratio. We experimentally validate this approach, demonstrate its robustness against intentional errors, and compare it to a naive direct measurement method. Furthermore, our technique is generalized to measure the amplitude of any general 2x2 unitary circuit, providing valuable insights for designing and testing a wide range of photonic integrated devices.

physics.optics↗

arXiv2024

Universal framework for anisotropic particles with resonance laws and splitting

Nanophotonics enables precise control over light-matter interactions, though most established design frameworks for subwavelength nanoparticles rely on isotropic materials. Uniaxial and biaxial particles -- common in natural and engineered systems -- introduce new degrees of freedom coupling geometry and material properties, unlocking multispectral and directional response in previously unexplored spectral regions. We present a universal full-wave framework for eigenmodes and resonances in such nanoparticles. Closed-form solutions reveal axial-permittivity sum rules and anisotropy-induced symmetry breaking, producing resonance splitting and novel radiation patterns. Generalizing to ellipsoids enables geometric tuning of multispectral response, while analytic quality factors elucidate mode localization and loss. Full-wave simulations of h-BN and $\alpha$-MoO3 particles confirm the theory. This framework unifies the understanding of anisotropic nanostructures across optics, magnetism, and thermal transport, opening pathways to a new generation of photonic devices with tunable multispectral response and controlled emission with direct applications in sensing and imaging

physics.app-ph↗

arXiv2024

Efficient Robust Spontaneous Parametric Down-Conversion via Detuning Modulated Composite Segments Designs

Spontaneous Parametric Down Conversion (SPDC) holds a pivotal role in quantum physics, facilitating the creation of entangled photon pairs, heralded single photons and squeezed light, critical resources for many applications in quantum technologies. However, their production is susceptible to physical variations, posing limitations on their robust utility. To overcome these limitations, this work introduces a method to significantly enhance the reliability of entangled photon pair generation. This approach involves introducing a composite design scheme to the SPDC process. The design is based on the development of a theoretical composite segments framework for SU(1,1), offering increased error resilience and robustness of the process. The practical application is experimentally demonstrated by modulating the nonlinear coefficient of a KTP crystal for degenerate 532 nm to 1064 nm conversion, resulting in an effective sevenfold improvement in stability of photon-pair generation and coincidence rate against temperature fluctuations compared to conventional quasi-phase-matching techniques. Furthermore, the presented concept is applicable to other physical systems that exhibit SU(1,1) dynamics. This methodology can create a leap forward in quantum technologies by significantly enhancing stability and error tolerance, thus paving the way for a new generation of entangled photon sources, holding promise for quantum information processing, communication, and precision measurement applications.

quant-ph↗

arXiv2024

Localized Resonant Phonon Polaritons in Biaxial Nanoparticles

The discovery of localized plasmon polariton resonances has been pivotal in enabling tunability of the optical resonance. Recently, extensive research efforts have aimed to expand these achievements to other polaritonic states that exhibit less loss and in other spectral regions. However, these efforts were limited to isotropic or uniaxial structures, and an eigenmode theory was derived only for isotropic particles. Here, we present a breakthrough in synthesizing biaxial nanostructures that exhibit localized hyperbolic phonon resonances with high Q-factors in the mid-infrared. Furthermore, we develop a theory that predicts high-order resonances in anisotropic particles with coupling between the axial permittivites. Finally, we confirm the theoretical predictions through near-field measurements, which demonstrate the existence of both the first and higher-order resonant modes. Our findings provide the foundation for designing a new generation of anisotropic resonators with various applications in the mid-IR range. Our analysis applies to other fields, such as quasi-magnetostatics and heat conduction.

physics.optics↗

arXiv2024

Robust photonic quantum gates with large number of waveguide segments

Realizing quantum information processors is challenged by errors and noise across all platforms. While composite segmentation schemes have been proposed in many systems, their application to photonic quantum gates in dual-rail configurations has only recently been demonstrated. However, prior research has been limited to a small number of segments, full noise correlation, and has overlooked the inherent power loss in such designs. Here, we study the fidelity and power loss of composite designs for photonic quantum gates with a high number of segments of varying geometrical widths. Using numerical simulations, we analyze the relationship between gate performance and the number of waveguide segments, accounting for statistical error correlations and variances. Beyond effectively reducing the errors, an asymptotic scaling pattern of quantum gate fidelity and power loss is observed as the number of segments increases. This analysis is examined in Silicon and Lithium Niobate platforms, addressing practical implementation challenges. Our findings demonstrate that optimized multi-segment waveguide geometrical designs significantly enhance the robustness and efficiency of photonic quantum gates, paving the way for more reliable quantum information processors.

quant-ph↗

arXiv2023

Correlation thresholds for effective composite pulse quantum error mitigation

Composite pulse segmentation has emerged as a promising error mitigation technique for a wide range of physical systems. In recent years, composite schemes were applied as mitigation strategies for quantum information processing and quantum computing. However, most of these strategies assume full error correlation between segments, which can result in gates with worse fidelity performance compared to non-composite gates. In our research, we investigate how error correlations impact the fidelity of quantum gates within the composite segmentation framework. In our study, we prove the existence of a critical correlation threshold, above which the composite pulse method significantly enhances both the mean value and variance of the fidelity. To gain deeper insights, we analyze various properties of the threshold in the realm of integrated photonics, including the effects of geometrical variations and the limit where the number of segments approaches infinity. We numerically explore diverse scenarios, showcasing different aspects of the critical threshold within the photonic quantum gates framework. These findings contribute open new pathways of error mitigation strategies and their implications in quantum information processing.

quant-ph↗