Optics · Cross-listed from gr-qc
Mathematical framework for simulation of non-perturbative cavity optomechanics with plate-like dielectrics
Andrew Laeuger and Nancy Aggarwal
Cavity optomechanical models typically treat a sensor either as a perturbative polarizable object in a pre-existing optical field, or solve the field at a fixed
equilibrium and linearize in a fixed optical-mode basis. Neither self-consistently determines the spatially resolved cavity field, the optical force, the mechanical
equilibrium, and the back-action when a finite-thickness dielectric plate intercepts the entire optical mode and restructures the intracavity field. In this companion paper to [1], we develop that treatment by extending the
vacuum two-
photon formalism to finite-thickness planar dielectrics, incorporating their Fresnel reflection, internal propagation, optical forces, and mechanical back-action directly into the field equations. We derive the carrier and sideband transfer functions needed to describe the coupled optical-mechanical system, including optomechanical cooling and the response to external perturbations. The result is a systematic starting point for calculating detector response and noise budgets for cavity experiments with intracavity dielectrics, including gravitational wave detectors deploying levitated sensors.
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Optics · Cross-listed from physics.flu-dyn
A complete forward projection algorithm through cylindrical and spherical refractive windows
Shijie Zhong, Shiyong Tan, Xiaosi Zhang et al. (+2 more)
Cylindrical or spherical windows often appear in experiments and real applications. Measuring through those windows requires projecting 3D points to pixels, which is different to compute due to refraction. A point may have multiple projected images but cannot be efficiently determine with the existing projection
algorithms. Using the ray's conserved momenta, we reduce this projection to closed-form equations with a concave structure. As a result, we can successfully determine whether a 3D point has a single projection or multiple and compute those locations. In simulations, with one single search, we can recover images that iterative methods miss even with many restarts. A wand calibration based on it can reach the precision limit set by image noise, enabling accurate 3D particle tracking in a swirling flow through cylinder windows. This
algorithm shows how to predict visibility and multiple images through curved windows, shedding light for 3D pipe flow measurements, accurate underwater reconstruction, and many real applications.
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All authors Shijie Zhong, Shiyong Tan, Xiaosi Zhang, Yanying Li, Rui Ni
Optics
Zeptosecond-level timing-noise floor in optical-to-terahertz photomixing
William F. McGrew, James Greenberg, Scott C. Egbert et al. (+6 more)
Optical generation of terahertz (0.1 to 10\,THz) carriers can, in principle, preserve the spectral purity of an optical reference without the noise penalty associated with electronic frequency multiplication. Here, we identify and suppress the dominant excess-noise mechanisms that limit this conversion in high-power uni-travelling-carrier photodiodes. We characterize amplitude-to-phase conversion as functions of photocurrent and reverse bias and identify operating parameters to minimize the effect. We quantify the white phase noise introduced by optical amplification and show that this contribution can be eliminated by directly driving the photodiode with a high-power optical source. With the excess noise mitigated, we use cross-correlation phase-noise measurements to observe a white phase-noise floor of $-161.0$~dBc/Hz at 263.2~GHz, corresponding to a timing-noise floor of 7.6~zs/$\sqrt{\mathrm{Hz}}$. The remaining floor follows the photocurrent dependence expected from shot noise. Extending the measurement across the full WR-3.4 band, from 220 to 330~GHz, yields timing-noise floors below 10~zs/$\sqrt{\mathrm{Hz}}$ throughout, with a minimum of 6.0~zs/$\sqrt{\mathrm{Hz}}$. These results establish direct photomixing as a route to sub-10-zs/$\sqrt{\mathrm{Hz}}$ white timing-noise floors for continuous-wave sources at terahertz frequencies and identify the noise processes that must be controlled to reach this regime.
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All authors William F. McGrew, James Greenberg, Scott C. Egbert, Brendan M. Heffernan, Y. Lange Simmons, Tatsuya Tanigawa, Kazutoshi Kato, Tadao Nagatsuma, Antoine Rolland
Optics · Cross-listed from quant-ph
Ghost unitaries for loss-resilient photonic resource-state generation
Kevin J. Randles, Manuel H. Muñoz-Arias and Kevin Thompson
Entangled few-
photon states, such as Bell and Greenberger-Horne-Zeilinger (GHZ) states, are central resources for discrete-variable photonic
quantum information processing. In many architectures, these states are generated probabilistically by first heralding single
photons from biphoton sources and then interfering them in linear-optical
circuits. In this work, we show that the
entanglement structure of said biphoton sources can be directly exploited for noise-engineering to deliver higher quality resource states. Using the transpose identity of multi-mode squeezed
vacuum states, we introduce "ghost-
unitary" implementations in which the target resource-generation interferometer is applied to the heralding modes rather than to the delivered resource modes. When the dominant imperfection is interferometric loss, this relocation converts direct amplitude damping of the output into false-positive heralding events that require both higher-pair emission and
photon loss. In the low-squeezing regime, these events are parametrically suppressed, yielding higher-fidelity conditional resource states. We analyze this mechanism for single-
qubit states, two-
photon NOON states, Bell states, and a family of $n$-
qubit GHZ states, as well as for single-
qubit teleportation and type-I-fusion-based resource growth. Across these examples, we delineate finite parameter regimes in which ghost-
unitary implementations outperform direct implementations, with particular relevance to frequency-bin photonics where active linear-optical transformations can be relatively lossy. We also prove that, in the setting considered here, the direct implementation of the $n$-GHZ family delivers identically damped outputs: equivalent to the ideal state followed by uniform amplitude damping. This extends the known $n=2,3$ cases and provides a structural result of independent interest for photonic
quantum information processing.
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Optics
Observation of Photon Bunching in Broadband Multimode Thermal Light Enabled by Temporal Imaging
Filip Sośnicki, Michał Mikołajczyk, Sanjay Kapoor et al. (+3 more)
Photons emitted by incoherent sources exhibit temporal bunching, a fundamental manifestation of Bose-Einstein statistics first observed by Hanbury Brown and Twiss (HBT). While intensity correlation measurements originated in astronomy and are now central across
quantum technologies, biophysics, and spectroscopy, observing temporal bunching in broadband thermal light remains limited by detector temporal resolution. Conventional approaches - such as streak cameras or optical upconversion - introduce severe trade-offs in efficiency, bandwidth, or setup versatility. Here, we propose and demonstrate a third route: pre-detection temporal magnification of the optical field prior to measuring its intensity autocorrelation function in a conventional HBT setup. Using an electro-optic time lens with a temporal magnification of 660, we resolve the temporal intensity autocorrelation of broadband thermal light generated via non-degenerate spontaneous parametric down-conversion with a bandwidth of 250 GHz. This enables direct observation of thermal
photon bunching on sub-3.5 picosecond timescales without narrow spectral filtering, establishing pre-detection temporal imaging as a general platform for broadband statistical optics, with applications spanning ultrafast
quantum optics, biophysical imaging, and potentially stellar intensity interferometry.
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All authors Filip Sośnicki, Michał Mikołajczyk, Sanjay Kapoor, Dmitri B. Horoshko, Mikhail I. Kolobov, Michał Karpiński
Optics · Cross-listed from cond-mat.mes-hall
Spatial Engineering of Topological Quantum Matter with Structured Light
Matias Mustonen, Ali G. Moghaddam, Teemu Ojanen et al. (+1 more)
Structured light provides a powerful means of controlling matter while itself exhibiting nontrivial spatial
topology. Here, we show that these spatial structures can be harnessed to locally engineer the topological properties of matter. In a paradigmatic example of a topological
insulator with Dirac surface states driven by an optical skyrmion beam, we show that structured light spatially tailors the effective
Hamiltonian, yielding position-dependent topological gaps and Dirac velocities. The resulting gap modulation can create topological and trivial regions separated by optically defined interfaces, without introducing material boundaries or chemical modifications. We further show that the geometry of these interfaces can be controlled through the spatial structure of the light, in particular its orbital angular momentum. Our results establish structured light as a route to dynamically pattern topological phases and open a broader perspective on the interplay between
topology in light and matter, including the possibility of transferring topological characteristics between the two.
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All authors Matias Mustonen, Ali G. Moghaddam, Teemu Ojanen, Marco Ornigotti
Optics
Programmable Hard-X-Ray Spectral Comb Generation via Laser-Compton Scattering
Hao Zhang, 1Ji Qiang, Shukui Zhang et al. (+1 more)
Independent control of line spacing and offset underpins programmable frequency-comb spectroscopy, yet it has not been established for hard-X-ray sources based on inverse Compton scattering after electron transport and angular collection. Self-consistent multi-particle tracking and Li'enard-Wiechert radiation calculations model a transported 10 pC beam and its angle-integrated spectrum near 11 keV.
Laser pulse separation programs the comb spacing, while pulse-to-pulse phase translates the entire line grid at fixed spacing. The spacing model agrees within 0.52%, while transport and optics change the phase-transfer slope by less than 0.2%. At fixed electron spot size, the largest resolvable separation scales as the inverse square of normalized emittance; subnanometer bunches also produce a mode-locked train with 13.9 as spacing. This two-coordinate programmability enables phase-stepped multicolor measurements and offers routes to hard-X-ray Ramsey interferometry, coherent control of core and nuclear excitations, and attosecond nonlinear spectroscopy.
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All authors Hao Zhang, 1Ji Qiang, Shukui Zhang, Sergio Carbajo
Optics
Chiral Vector Beams for Topological Enantio-Sensitive Imaging
A. Rodriguez, J. Edginton, A. Löhr et al. (+7 more)
Molecular chiral discrimination is vital across chemistry and life sciences, yet optical approaches remain highly inefficient for small organic molecules. Here we turn vector beams, whose polarization carries a topological charge, into an efficient probe of molecular handedness. We show that the combination of a tightly focused radially polarized beam at the fundamental frequency {\omega} and an azimuthally polarized beam at 2{\omega} creates chiral vector beams, a locally chiral field with structured handedness. Using state-of-the-art computational modeling in the chiral molecule carvone, we show that the nonlinear response (notably sum-frequency generation) of randomly oriented chiral molecules to this chiral vector beam captures the fields' local handedness and is highly enantio-sensitive. The two enantiomers emit light at frequency 3{\omega} with topological ring structures of different divergence, and thus the molecular handedness can be read out directly from the ring radius. The signal inherits the Poincaré index of the driving field, opening up new ways to robust, ultrafast, and and all-optical chiral discrimination.
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All authors A. Rodriguez, J. Edginton, A. Löhr, J. Terentjevas, P. Vindel-Zandbergen, A. Ordóñez, J. Vogwell, O. Smirnova, D. Ayuso, L. Rego
Optics
Image Priors for Single-Shot Coded Diffraction Phase Retrieval
Zhiyuan Hu, YoonSeok Baek, Sylvain Gigan et al. (+2 more)
Phase
retrieval recovers complex-valued objects from intensity-only measurements. In its classical
Fourier form, reconstruction suffers from twin-image stagnation. Coded diffraction imaging, which adds a random phase mask before the
Fourier transform, has so far required several masks. We show that an image prior makes single-shot coded diffraction imaging possible, with a single random mask followed by a
Fourier transform. We validate this claim in simulation and in an optical experiment, in which a spatial light modulator displays the phase object together with the random mask. Our experimental validation covers five test signals and 530 images from the public Brno quantitative phase microscopy
dataset of five adherent
cell lines. With no image prior or with
Fourier-only measurements, reconstruction of complex-valued objects from a single diffraction pattern consistently fails. An out-of-the-box pretrained image denoiser enables accurate reconstruction, in simulation even with fewer measurements than unknowns. Five regularization frameworks built on the same denoiser and one learned weakly convex regularizer all reconstruct the experimental images with peak signal-to-noise ratios within one decibel of each other. A single random phase mask and image priors thus turn coded diffraction imaging into a practical single-shot modality for quantitative phase imaging.
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All authors Zhiyuan Hu, YoonSeok Baek, Sylvain Gigan, Michael Unser, Jonathan Dong
Optics · Cross-listed from quant-ph
Direct polarisation-state reconstruction with a temporal pointer: accessible states, resolution and optimal coupling
Shane P. Gervais and Lambert Giner
Weak measurements are used to amplify small signals, to address foundational questions, and to characterise
quantum states without
tomography. In direct state reconstruction each amplitude of the state vector is proportional to a single complex weak value, which for a temporal pointer is read from the mean arrival time and the mean frequency of the postselected pulse. Such an experiment requires three quantities to be fixed, the coupling, the angular resolution demanded of the reconstruction, and the set of states over which the method remains usable, and these are commonly set by the available apparatus rather than derived. We derive all three for a Gaussian temporal pointer and an arbitrary postselection state. The states that cannot be reconstructed form a spherical cap centred on the state orthogonal to the postselection, whose geodesic half-angle follows from the largest of three independent thresholds and involves no adjustable parameter. Two states are distinguishable only if they differ by more than a minimal step fixed by the coupling, by the number of incident
photons and by the sensitivity of the weak value along the path followed. For an inversion at first order in the coupling the systematic and statistical errors are opposed and fix an optimal coupling that varies as the inverse sixth root of the number of incident
photons, whereas an exact inversion at finite coupling removes the systematic error, the remaining bound being one on the two-centroid readout rather than on the inversion, since below an amplitude equal to a quarter of the coupling two states give the same pair of centroids while their profiles differ. These results allow a direct reconstruction experiment to be dimensioned before the apparatus is assembled.
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Optics · Cross-listed from math.AP
Limit cycles govern wave energy accumulation in space-time-varying materials
Bryn Davies and Erik Orvehed Hiltunen
We study the amplification and concentration of wave energy in smooth, periodic space-time media through the dynamics of the characteristic curves of the associated wave equation. In an impedance-matched setting, we show that stable limit cycles attract neighbouring characteristics, focusing the wave energy density. The exponential attraction rate is estimated analytically from the system's Lyapunov exponent. We further show that the attraction of characteristics and energy accumulation persist under a range of nonperiodic perturbations. Finally, we present a Floquet-
Fourier numerical method for computing stable and unstable limit cycles and their attraction rates. Throughout, we exemplify the results using the example of modulation given by a superposition of travelling waves, revealing saddle–node bifurcations where limit cycles may appear depending on the relative wave speeds. Full-wave simulations confirm that the characteristic mechanism continues to describe energy accumulation beyond the impedance-matched case.
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Optics
Finite-event modulation transfer through forward-scattering media
Chong Wang, Liangfeng Hu, Yuchen He et al. (+5 more)
How spatial structure is transferred through a forward-scattering medium depends jointly on pattern scale and propagation distance. Starting from
photon exit displacements, we derive modulation transfer while retaining the number, depths, and projected angles of individual deflections, with event occurrences described by a homogeneous Poisson process along the propagation path. The second angular moment yields a leading low-frequency loss proportional to $k^2z^3$, where $k$ is angular spatial frequency and $z$ is thickness. At finite frequency, the model predicts two coupled departures: loss bends below its low-frequency quadratic extrapolation at fixed thickness, and transfer curves separate by thickness at fixed $k^2z^3$. The leading corrections to both effects arise from the same fourth angular moment. For symmetric, nondegenerate projected-angle distributions, the full response further establishes increasing loss with thickness in the same medium at fixed joint variable. Binary-pattern measurements through TiO$_2$ suspensions span five nominal loadings, seven thicknesses, and 20 spatial frequencies, supporting the approximate low-frequency scaling and showing both departures. A Gaussian effective-angle response calibrated only on lower-frequency data predicts the held-out higher-frequency band without refitting, with a logarithmic root-mean-square error of 0.0181 compared with 0.1021 for quadratic extrapolation. The results show that finite-event statistics provide a common physical origin for spectral bending and thickness-dependent departure from low-frequency scaling, linking coarse-pattern transport to finer spatial structure.
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All authors Chong Wang, Liangfeng Hu, Yuchen He, Huaibin Zheng, Hui Chen, Jianbin Liu, Yu Zhou, Zhuo Xu
Optics
Asynchronous Terahertz-field sampling with soliton microcombs
Alexandra Sakharova, Alexander E. Ulanov, Konstantin Wenzel et al. (+6 more)
Terahertz time-domain spectroscopy records the electric field of terahertz transients and underpins applications from materials science to non-destructive testing. Asynchronous optical sampling enables systems without moving parts, but its acquisition rate remains fundamentally limited by the repetition-rate of the driving femtosecond
lasers. Here, we demonstrate asynchronous terahertz-field sampling with two chip-based
soliton microcombs. Their ultrahigh 25 GHz pulse repetition-rate drastically reduces dead-time during acquisition, and stabilization via sideband injection-locking enables coherent averaging without active feedback loops. At 10 kHz acquisition rate, we achieve a dynamic range of 74 dB in a single 100 $\mu$s scan, and 100 dB after 50 ms of coherent averaging with a 1.6 THz bandwidth. Acquisition rates of up to 100 kHz are demonstrated, limited only by detection electronics. Together with a proof-of-concept silicon wafer thickness measurement, these results establish
soliton microcombs as compact sources for rapid terahertz-field sampling.
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All authors Alexandra Sakharova, Alexander E. Ulanov, Konstantin Wenzel, Milan Deumer, Alexander Dohms, Bastian Ruhnke, Lars Liebermeister, Robert B. Kohlhaas, Tobias Herr
Optics
Fading Memory and Nonlinear Dynamics in a Microring Resonator Network and their Use in Computation
Alessandro Foradori, Alessio Lugnan, Lorenzo Pavesi et al. (+1 more)
Silicon microring resonators are promising components for photonic reservoir computing because their nonlinear optical response can transform signals and retain information about recent inputs. Under constant optical excitation, their coupled free-carrier and thermal dynamics can generate self-pulsing: a periodic output response. However, constant-input behavior does not reveal how these dynamics respond to randomly modulated signals or whether their
memory is useful for temporal processing. Here, we characterize a single silicon microring resonator and a passive network of microring resonators under random input modulation. The temporal component associated with self-pulsing remains observable under random modulation, but the largest fading
memory occurs near the self-pulsing boundary, where no resolved self-pulsing-like oscillation is present. reservoir computing metrics, such as
memory capacity, map this accessible
memory, and its decay provides effective timescales associated mainly with free-carrier and thermal relaxation. Finally, we use NARMA reconstruction to test whether the measured
memory profile supports nonlinear temporal processing. Responses with a resolved self-pulsing-like component perform worse on this task, and the intrinsic
memory profile is not matched to the required input history. These results show that reservoir computing metrics can characterize nonlinear microring resonator dynamics even when the physical system is not an effective standalone reservoir for the selected task.
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All authors Alessandro Foradori, Alessio Lugnan, Lorenzo Pavesi, Peter Bienstman
Optics
High Sensitivity Transient Holographic Full-Polarization Microscopy
Julia A. Gessner, Philipp Kollenz, Godwin Maliyekkal et al. (+6 more)
The polarization state of light provides direct access to ultrafast electronic,
magnetic, and structural dynamics in materials. Transient wide-field microscopy with simultaneous amplitude, phase, and polarization sensitivity enables spatially resolved measurements of these dynamics, but its sensitivity is often limited by technical noise and background fluctuations. Here, we demonstrate transient holographic full-polarization microscopy with substantially reduced instrumental noise and sensitivity approaching the shot-noise limit. We compare holographic geometries using one, two, and four reference beams and find that the single-reference configuration provides the most favourable shot-noise-limited sensitivity for the derived polarization observables. Combined with two-camera detection, it simultaneously captures both orthogonal polarization components without distributing reference
photons among multiple carriers. A self-referenced noise-reduction framework combining singular value decomposition and background subtraction further suppresses correlated noise. For spatially averaged regions, the baseline noise is reduced by factors of three-sixty, enabling detection of weaker transient responses at lower excitation densities and in weakly absorbing materials.
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All authors Julia A. Gessner, Philipp Kollenz, Godwin Maliyekkal, Milena R. Neubert, Garrett May, Lukas Becker, Nasrin Solhtalab, Tiago Buckup, Felix Deschler
Optics · Cross-listed from quant-ph
Metasurface quantum graphs for polarization-independent certified randomness
Xing Lin, Wenwen Liu, Wange Song et al. (+2 more)
Quantum random number generators are crucial for information security, yet existing implementations are hindered by bulky optics, device imperfections, and state
alignment constraints. Here, using a compact metasurface platform, we achieve polarization-independent certified randomness by establishing a quantitative
quantum graph framework. By mapping multi-channel nanophotonic responses onto graph vertices, we assign metasurface measurements an operational information-theoretic meaning, directly connecting weighted graph degrees to conditional min-
entropy estimation. The resulting graph-certified measurements yield robust private randomness even under
entanglement-based attacks without complex optics. Experimentally, we fabricate 4- and 6-channel dielectric metasurfaces to implement high-dimensional positive operator-valued measure graphs, successfully certifying randomness with heralded single
photons and Poissonian light. By integrating complex
quantum measurements into a single passive layer, our metasurface
quantum graphs provide a scalable route for integrated
quantum technologies.
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All authors Xing Lin, Wenwen Liu, Wange Song, Sixin Chen, Shuang Zhang
Optics
Programmable spatiotemporal shaping for partially coherent structured wave packets
Zhao Zhang, Haihao Fan, Yaning Zhou et al. (+5 more)
Providing more coherent light with space-time coupling offers unprecedented opportunities across diverse scientific disciplines and areas of technology. However, in many applications, tailored
laser beams with partial coherence in space and time are desired. Here, we demonstrate a programmable approach for simultaneously shaping the intensity and coherence distributions of spatiotemporally coupled partially coherent wave packets. By jointly engineering the fractal speckle of a dynamic scatterer and applying tailored modulation of the illumination function, we experimentally generate partially coherent
laser beams with arbitrarily designed intensity and nontrivial coherence distributions. The proposed approach is compatible with ultrafast
laser pulses, enabling the on-demand generation of partially coherent space-time wave packets. The resulting spatiotemporally partially coherent wave packets exhibit non-separable space-time intensity profiles together with engineered spatiotemporal correlation distributions. This work provides a versatile framework for tailoring partially coherent light in space and time, with varied applications in relativistic
laser-matter interaction, passive imaging and optical manipulation.
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All authors Zhao Zhang, Haihao Fan, Yaning Zhou, Weiran Li, Chaoliang Ding, Qiwen Zhan, Yangjian Cai, Xin Liu
Optics · Cross-listed from quant-ph
Multipolar Nanophotonics with Quantum Computers
Alex Krasnok
Small particles respond to light through electric and
magnetic patterns called multipoles. Their interference determines the direction of scattered light and affects the decay of nearby emitters. Larger nanoantenna arrays, metasurfaces, and other nanophotonic systems demand increasingly costly simulations to meet strict performance and reliability requirements. We show how to represent these responses with
quantum bits (
qubits) and use
quantum circuits to calculate scattering and the Purcell effect, the change in an emitter's decay rate caused by its surroundings. The
circuits can encode known multipoles or estimate unknown ones from Maxwell's equations at the particle surface. We test the method against classical theory using an ideal
quantum simulator and real IBM and IonQ
quantum computers. For a silicon nanoparticle of radius 78 nm illuminated at 679 nm, IonQ gives a forward directivity of 2.984, close to the ideal dipolar value 3, quantifying the concentration of scattered light in the forward direction. For an emitter 10 nm from a gold nanoparticle and emitting at 510 nm, IBM measurements yield a calculated total decay rate 20.48 times its
vacuum value versus 20.47 from theory, with correction for errors in reading the
qubit states. We also establish how the number of multipoles and the required accuracy set the demands on
qubits and measurements. These results motivate
quantum-assisted design studies of directional radiation and emitter decay in nanophotonic systems.
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