arXiv subjects

Guanhao Huang

Publications and source records attributed to Guanhao Huang.

At least 19 recordsLinked to original sources

arXiv2026

Ultracoherent self-assembled diamond nanomechanics reveals superfluid dynamics

From gravitational-wave detection, protein force microscopy, to exploration of quantum-classical boundaries, many anticipated discoveries in fundamental science require improving measurement sensitivity limits. Through the fluctuation-dissipation theorem, mechanical dissipation sets the acoustic noise for this limit. Yet, even in high-purity crystals, the microscopic mechanisms responsible for the acoustic loss remain poorly understood. Tension-induced dissipation dilution offers a route to ultralow acoustic loss, but is challenging to implement in crystalline materials including single-crystal diamond. Here we realize a strain-engineered diamond nanomechanical platform using a liquid-assisted van der Waals self-assembly process that harnesses intrinsic surface forces to apply tensile stress exceeding 1 GPa. At cryogenic temperatures these resonators achieve quality factors beyond 10 billion (intrinsic material quality factors beyond 100 million). This exceptional coherence turns them into a sensitive probe for residual dissipation, elucidating three distinct two-level-system channels and one topological dissipation channel from a surface superfluid helium film. Our work shows how advancing mechanical coherence opens access to new regimes of physics in hybrid quantum systems, precision metrology, and condensed-matter physics.

cond-mat.mes-hall↗

arXiv2025

Electrons herald non-classical light

Free electrons are a widespread and universal source of electromagnetic fields. The past decades witnessed ever-growing control over many aspects of electron-generated radiation, from the incoherent emission produced by X-ray tubes to the exceptional brilliance of free-electron lasers. Reduced to the elementary process of quantized energy exchange between individual electrons and the electromagnetic field, electron beams may facilitate future sources of tunable quantum light. However, the quantum features of such radiation are tied to the correlation of the particles, calling for the joint electronic and photonic state to be explored for further applications. Here, we demonstrate the coherent parametric generation of non-classical states of light by free electrons. We show that the quantized electron energy loss heralds the number of photons generated in a dielectric waveguide. In Hanbury-Brown-Twiss measurements, an electron-heralded single-photon state is revealed via antibunching intensity correlations, while two-quantum energy losses of individual electrons yield pronounced two-photon coincidences. The approach facilitates the tailored preparation of higher-number Fock and other optical quantum states based on controlled interactions with free-electron beams.

quant-ph↗

arXiv2025

High Finesse Buckled Microcavities

Optical cavities are widely used in modern science and technology to enable a wide range of both quantum and classical applications. Recently, the growing demand for miniaturization and high performance has fueled the exploration of new fabrication methods beyond traditional polishing techniques and macroscopic mirrors. Visible and near-infrared (NIR) wavelengths are particularly important for quantum applications, where achieving low-loss resonators is also more challenging than in the telecom range, presenting unique challenges and opportunities for microscopic cavity systems. Here, we present a novel fabrication method for making NIR microcavities using buckled dielectric membrane mirrors, achieving a record finesse of 0.9 million at 780 nm. We demonstrated flexible device geometries, including singular mirrors and mirror arrays, featuring radii of curvature ranging from 1 mm to 10 mm. The fabrication process offers high uniformity, high yield, and robust performance across a wide range of cavity lengths. Additionally, we can produce easy-to-assemble microcavity packages, with a total volume of ~2 (4) $\,\mathrm{mm}^3\,$, featuring optical modes with a linewidth of 5.16 MHz (570 kHz) and a free spectral range of 3.18 THz (150 GHz). Our results extend the frontier of microcavity fabrication for classical and quantum photonic technologies.

physics.optics↗

arXiv2025

Universal dynamics and microwave control of programmable cavity electro-optic frequency combs

Electro-optic (EO) frequency combs are foundational for metrology and spectroscopy. Specifically, microresonator-based cavity EO combs are distinguished by efficient sideband generation, precisely controlled by microwave signals, enabling high-performance integrated frequency references and pulse sources. However, the apparent simplicity of these devices, often described by the EO modulation-induced coupling of nearest-neighbor cavity modes, has limited investigations of their fundamental physics, thereby restricting their full potential. Here, we uncover the universal dynamics and complete frequency lattice connectivity underpinning cavity EO microcombs, as well as characterize the full space of nonlinear optical states, controlled by modulation depth and optical detuning, using the thin-film lithium niobate photonic platform. Leveraging this understanding, we design complex long-range couplings between cavity modes to realize programmable spectro-temporal shaping of the generated combs and pulses. We achieve three technological advances, including repetition-rate flexibility, substantial comb bandwidth extension beyond traditional scaling laws, and resonantly-enhanced flat-top spectrum. Our results provide physical insights for synchronously driven cavity-based EO systems, broadly defined, paving the way for electrically controlled and electrically enhanced comb generators for next-generation photonic applications.

physics.optics↗

arXiv2025

Stable gigahertz- and mmWave-repetition-rate soliton microcombs on X-cut lithium niobate

Soliton microcombs are a cornerstone of integrated frequency comb technologies, with applications spanning photonic computing, ranging, microwave synthesis, optical communications, and quantum light generation. In nearly all such applications, electro-optic (EO) components play a critical role in generating, monitoring, stabilizing, and modulating the solitons. Towards building photonic integrated circuits for next-generation applications, that will simultaneously maximize system performance and minimize size, weight, and power consumption metrics, achieving soliton microcombs and efficient EO modulation on a chip is essential. X-cut thin-film lithium niobate (TFLN) has emerged as a leading photonic platform for the realization of high-performance integrated EO devices and systems. However, despite extensive research, soliton microcombs have remained elusive to X-cut TFLN due to its multiple strong Raman-active modes, in-plane refractive index anisotropy, and photorefractive effects. Here, we address this long-standing challenge and demonstrate versatile soliton microcombs on X-cut TFLN, with repetition-rates spanning from the gigahertz (~26 GHz) up to the millimeter-wave (~0.156 THz) regime. The combs feature exceptional long-term stability, maintaining a direct injection-locked state for over 90 minutes (manually terminated), with repetition-rate phase noise closely tracking that of a high-quality electronic microwave synthesizer. Our finding broadly advances both the fundamental science and practical applications of integrated comb sources by enabling efficient EO modulation and broadband coherent solitons to be monolithically combined on the same chip.

physics.optics↗

arXiv2024

Motional sideband asymmetry of a solid-state mechanical resonator at room temperature

The motional sideband asymmetry of a mechanical oscillator interacting with a laser field can be observed when approaching the quantum ground state, where the zero-point energy of the mechanical oscillator becomes a sizable contribution to its motion. In the context of quantum optomechanics, it allows, in principle, calibration-free inference of the thermal equilibrium of a macroscopic mechanical resonator with its optical bath. At room temperature, this phenomenon has been observed in pioneering experiments using levitated nanoparticles. Measuring this effect with solid-state mechanical resonators has been compounded by thermal intermodulation noise, mirror frequency noise and low quantum cooperativity. Here, we sideband-cool a membrane-in-the-middle system close to the quantum ground state from room temperature, and observe motional sideband asymmetry in a dual-homodyne measurement. Sideband thermometry yields a minimum phonon occupancy of $\bar{n}_{eff}=9.5$. Our work provides insights into nonlinear optomechanical dynamics at room temperature and facilitates accessible optomechanical quantum technologies without the need for complex feedback control and cryogenic cooling.

quant-ph↗

arXiv2024

Fundamental charge noise in electro-optic photonic integrated circuits

Understanding thermodynamical measurement noise is of central importance for electrical and optical precision measurements from mass-fabricated semiconductor sensors, where the Brownian motion of charge carriers poses limits, to optical reference cavities for atomic clocks or gravitational wave detection, which are limited by thermorefractive and thermoelastic noise due to the transduction of temperature fluctuations to the refractive index and length fluctuations. Here, we discover that unexpectedly charge carrier density fluctuations give rise to a novel noise process in recently emerged electro-optic photonic integrated circuits. We show that Lithium Niobate and Lithium Tantalate photonic integrated microresonators exhibit an unexpected Flicker type (i.e. $1/f^{1.2}$) scaling in their noise properties, significantly deviating from the well-established thermorefractive noise theory. We show that this noise is consistent with thermodynamical charge noise, which leads to electrical field fluctuations that are transduced via the strong Pockels effects of electro-optic materials. Our results establish electrical Johnson-Nyquist noise as the fundamental limitation for Pockels integrated photonics, crucial for determining performance limits for both classical and quantum devices, ranging from ultra-fast tunable and low-noise lasers, Pockels soliton microcombs, to quantum transduction, squeezed light or entangled photon-pair generation. Equally, this observation offers optical methods to probe mesoscopic charge fluctuations with exceptional precision.

physics.optics↗

arXiv2024

The planted XY model: thermodynamics and inference

In this paper we study a fully connected planted spin glass named the planted XY model. Motivation for studying this system comes both from the spin glass field and the one of statistical inference where it models the angular synchronization problem. We derive the replica symmetric (RS) phase diagram in the temperature, ferromagnetic bias plane using the approximate message passing (AMP) algorithm and its state evolution (SE). While the RS predictions are exact on the Nishimori line (i.e. when the temperature is matched to the ferromagnetic bias), they become inaccurate when the parameters are mismatched, giving rise to a spin glass phase where AMP is not able to converge. To overcome the defects of the RS approximation we carry out a one-step replica symmetry breaking (1RSB) analysis based on the approximate survey propagation (ASP) algorithm. Exploiting the state evolution of ASP, we count the number of metastable states in the measure, derive the 1RSB free entropy and find the behavior of the Parisi parameter throughout the spin glass phase.

cond-mat.dis-nn↗

arXiv2023

Room-temperature quantum optomechanics using an ultra-low noise cavity

Ponderomotive squeezing of light, where a mechanical oscillator creates quantum correlations between the phase and amplitude of the interacting light field, is a canonical signature of the quantum regime of optomechanics. At room temperature, this has only been reached in pioneering experiments where an optical restoring force controls the oscillator stiffness, akin to the vibrational motion of atoms in an optical lattice. These include both levitated nanoparticles and optically-trapped cantilevers. Recent advances in engineered mechanical resonators, where the restoring force is provided by material rigidity rather than an external optical potential, have realized ultra-high quality factors (Q) by exploiting `soft clamping'. However entering the quantum regime with such resonators, has so far been prevented by optical cavity frequency fluctuations and thermal intermodulation noise. Here, we overcome this challenge and demonstrate optomechanical squeezing at room temperature in a phononic-engineered membrane-in-the-middle system. By using a high finesse cavity whose mirrors are patterned with phononic crystal structures, we reduce cavity frequency noise by more than 700-fold. In this ultra-low noise cavity, we introduce a silicon nitride membrane oscillator whose density is modulated by silicon nano-pillars, yielding both high thermal conductance and a localized mechanical mode with Q of 1.8e8. These advances enable operation within a factor of 2.5 of the Heisenberg limit, leading to squeezing of the probing field by 1.09 dB below the vacuum fluctuations. Moreover, the long thermal decoherence time of the membrane oscillator (more than 30 vibrational periods) allows us to obtain conditional displaced thermal states of motion with an occupation of 0.97 phonon, using a multimode Kalman filter. Our work extends quantum control of engineered macroscopic oscillators to room temperature.

quant-ph↗

arXiv2023

Free-electron interaction with nonlinear optical states in microresonators

The short de Broglie wavelength and strong interaction empower free electrons to probe scattering and excitations in materials and resolve the structure of biomolecules. Recent advances in using nanophotonic structures to mediate bilinear electron-photon interaction have brought novel optical manipulation schemes to electron beams, enabling high space-time-energy resolution electron microscopy, quantum-coherent optical modulation, attosecond metrology and pulse generation, transverse electron wavefront shaping, dielectric laser acceleration, and electron-photon pair generation. However, photonic nanostructures also exhibit nonlinearities, which have to date not been exploited for electron-photon interactions. Here, we report the interaction of electrons with spontaneously generated Kerr nonlinear optical states inside a continuous-wave driven photonic chip-based microresonator. Optical parametric processes give rise to spatiotemporal pattern formation, or dissipative structures, corresponding to coherent or incoherent optical frequency combs. By coupling such microcombs in situ to electron beams, we demonstrate that different dissipative structures induce distinct fingerprints in the electron spectra and Ramsey-type interference patterns. In particular, using spontaneously formed femtosecond temporal solitons, we achieve ultrafast temporal gating of the electron beam without the necessity of a pulsed laser source or a pulsed electron source. Our work elucidates the interaction of free electrons with a variety of nonlinear dissipative states, demonstrates the ability to access solitons inside an electron microscope, and extends the use of microcombs to unexplored territories, with ramifications in novel ultrafast electron microscopy, light-matter interactions driven by on-chip temporal solitons, and ultra-high spatiotemporal resolution sampling of nonlinear optical dynamics and devices.

physics.optics↗

arXiv2022

Quantum state heralding using photonic integrated circuits with free electrons

Recently, integrated photonic circuits have brought new capabilities to electron microscopy and been used to demonstrate efficient electron phase modulation and electron-photon correlations. Here, we quantitatively analyze the feasibility of high fidelity and high purity quantum state heralding using a free electron and a photonic integrated circuit with parametric coupling, and propose schemes to shape useful electron and photonic states in different application scenarios. Adopting a dissipative quantum electrodynamics treatment, we formulate a framework for the coupling of free electrons to waveguide spatial-temporal modes. To avoid multimode-coupling induced state decoherence, we show that with proper waveguide design, the interaction can be reduced to a single-mode coupling to a quasi-TM00 mode. In the single-mode coupling limit, we go beyond the conventional state ladder treatment, and show that the electron-photon energy correlations within the ladder subspace can still lead to a fundamental purity and fidelity limit on complex optical and electron state preparations through heralding schemes. We propose applications that use this underlying correlation to their advantage, but also show that the imposed limitations for general applications can be overcome by using photonic integrated circuits with an experimentally feasible interaction length, showing its promise as a platform for free-electron quantum optics.

quant-ph↗

arXiv2022

Ultrafast tunable lasers using lithium niobate integrated photonics

Recent advances in the processing of thin-film LNOI have enabled low-loss photonic integrated circuits, modulators with improved half-wave voltage, electro-optic frequency combs and novel on-chip electro-optic devices, with applications ranging from 5G telecommunication and microwave photonics to microwave-to-optical quantum interfaces. Lithium niobate integrated photonic circuits could equally be the basis of integrated narrow-linewidth frequency-agile lasers. Pioneering work on polished lithium niobate crystal resonators has led to the development of electrically tunable narrow-linewidth lasers. Here we report low-noise frequency-agile lasers based on lithium niobate integrated photonics and demonstrate their use for coherent laser ranging. This is achieved through heterogeneous integration of ultra-low-loss silicon nitride photonic circuits with thin-film lithium niobate via direct wafer bonding. This platform features low propagation loss of 8.5 dB/m enabling narrow-linewidth lasing (intrinsic linewidth of 3 kHz) by self-injection locking to a III-V semiconductor laser diode. The hybrid mode of the resonator allows electro-optical laser frequency tuning at a speed of 12 PHz/s with high linearity, low hysteresis and while retaining narrow linewidth. Using this hybrid integrated laser, we perform a proof-of-concept FMCW LiDAR ranging experiment, with a resolution of 15 cm. By fully leveraging the high electro-optic coefficient of lithium niobate, with further improvements in photonic integrated circuits design, these devices can operate with CMOS-compatible voltages, or achieve mm-scale distance resolution. Endowing low loss silicon nitride integrated photonics with lithium niobate, gives a platform with wide transparency window, that can be used to realize ultrafast tunable lasers from the visible to the mid-infrared, with applications from OCT and LiDAR to environmental sensing.

physics.optics↗

arXiv2022

Scalable and Programmable Phononic Network with Trapped Ions

Controllable bosonic systems can provide post-classical computational power with sub-universal quantum computational capability. A network that consists of a number of bosons evolving through beam-splitters and phase-shifters between different modes, has been proposed and applied to demonstrate quantum advantages. While the network has been implemented mostly in optical systems with photons, recently alternative realizations have been explored, where major limitations in photonic systems such as photon loss, and probabilistic manipulation can be addressed. Phonons, the quantized excitations of vibrational modes, of trapped ions can be a promising candidate to realize the bosonic network. Here, we experimentally demonstrate a minimal-loss phononic network that can be programmed and in which any phononic states are deterministically prepared and detected. We realize the network with up to four collective-vibrational modes, which can be straightforwardly extended to reveal quantum advantage. We benchmark the performance of the network with an exemplary algorithm of tomography for arbitrary multi-mode states with a fixed total phonon number. We obtain reconstruction fidelities of 94.5 $\pm$ 1.95 % and 93.4 $\pm$ 3.15 % for single-phonon and two-phonon states, respectively. Our experiment demonstrates a clear and novel pathway to scale up a phononic network for various quantum information processing beyond the limitations of classical and other quantum systems.

quant-ph↗

arXiv2022

Dissipative Quantum Feedback in Measurements Using a Parametrically Coupled Microcavity

Micro- and nanoscale optical or microwave cavities are used in a wide range of classical applications and quantum science experiments, ranging from precision measurements, laser technologies to quantum control of mechanical motion. The dissipative photon loss via absorption, present to some extent in any optical cavity, is known to introduce thermo-optical effects and thereby impose fundamental limits on precision measurements. Here, we theoretically and experimentally reveal that such dissipative photon absorption can result in quantum feedback via in-loop field detection of the absorbed optical field, leading to the intracavity field fluctuations to be squashed or antisquashed. Strikingly, this modifies the optical cavity susceptibility in coherent response measurements and causes excess noise and correlations in incoherent interferometric optomechanical measurements using a cavity. We experimentally observe such unanticipated dissipative dynamics in optomechanical spectroscopy of sideband-cooled optomechanical crystal cavitiess at both cryogenic temperature (approximately 8 K) and ambient conditions. The dissipative feedback introduces effective modifications to the optical cavity linewidth and the optomechanical scattering rate and gives rise to excess imprecision noise in the interferometric quantum measurement of mechanical motion. Such dissipative feedback differs fundamentally from a quantum nondemolition feedback, e.g., optical Kerr squeezing. The dissipative feedback itself always results in an antisqueezed out-of-loop optical field, while it can enhance the coexisting Kerr squeezing under certain conditions. Our result has wide-ranging implications for future dissipation engineering, such as dissipation enhanced sideband cooling and Kerr squeezing, quantum frequency conversion, and nonreciprocity in photonic systems.

quant-ph↗

arXiv2022

Reduced Material Loss in Thin-film Lithium Niobate Waveguides

Thin-film lithium niobate has shown promise for scalable applications ranging from single-photon sources to high-bandwidth data communication systems. Realization of the next generation high-performance classical and quantum devices, however, requires much lower optical losses than the current state of the art ($\sim$10 million). Unfortunately, material limitations of ion-sliced thin-film lithium niobate have not been explored, and therefore it is unclear how high-quality factor can be achieved in this platform. Here we evaluate the material limited quality factor of thin-film lithium niobate photonic platform can be as high as $Q\approx 1.8\times10^{8}$ at telecommunication wavelengths, corresponding to a propagation loss of 0.2 dB/m.

physics.optics↗

arXiv2021

Nanomechanical resonators with ultra-high-$Q$ perimeter modes

Systems with low mechanical dissipation are extensively used in precision measurements such as gravitational wave detection, atomic force microscopy and quantum control of mechanical oscillators via opto- and electromechanics. The mechanical quality factor ($Q$) of these systems determines the thermomechanical force noise and the thermal decoherence rate of mechanical quantum states. While the dissipation rate is typically set by the bulk acoustic properties of the material, by exploiting dissipation dilution, mechanical $Q$ can be engineered through geometry and increased by many orders of magnitude. Recently, soft clamping in combination with strain engineering has enabled room temperature quality factors approaching one billion ($10^9$) in millimeter-scale resonators. Here we demonstrate a new approach to soft clamping which exploits vibrations in the perimeter of polygon-shaped resonators tethered at their vertices. In contrast to previous approaches, which rely on cascaded elements to achieve soft clamping, perimeter modes are soft clamped due to symmetry and the boundary conditions at the polygon vertices. Perimeter modes reach $Q$ of 3.6 billion at room temperature while spanning only two acoustic wavelengths -- a 4-fold improvement over the state-of-the-art mechanical $Q$ with 10-fold smaller devices. The small size of our devices makes them well-suited for near-field integration with microcavities for quantum optomechanical experiments. Moreover, their compactness allows the realization of phononic lattices. We demonstrate a one-dimensional Su-Schrieffer-Heeger chain of high-$Q$ perimeter modes coupled via nearest-neighbour interaction and characterize the localized edge modes.

physics.app-ph↗

arXiv2021

Probing material absorption and optical nonlinearity of integrated photonic materials

Optical microresonators with high quality ($Q$) factors are essential to a wide range of integrated photonic devices. Steady efforts have been directed towards increasing microresonator $Q$ factors across a variety of platforms. With success in reducing microfabrication process-related optical loss as a limitation of $Q$, the ultimate attainable $Q$, as determined solely by the constituent microresonator material absorption, has come into focus. Here, we report measurements of the material-limited $Q$ factors in several photonic material platforms. High-$Q$ microresonators are fabricated from thin films of SiO$_2$, Si$_3$N$_4$, Al$_{0.2}$Ga$_{0.8}$As and Ta$_2$O$_5$. By using cavity-enhanced photothermal spectroscopy, the material-limited $Q$ is determined. The method simultaneously measures the Kerr nonlinearity in each material and reveals how material nonlinearity and ultimate $Q$ vary in a complementary fashion across photonic materials. Besides guiding microresonator design and material development in four material platforms, the results help establish performance limits in future photonic integrated systems.

physics.optics↗

arXiv2020

High-yield wafer-scale fabrication of ultralow-loss, dispersion-engineered silicon nitride photonic circuits

Low-loss photonic integrated circuits (PIC) and microresonators have enabled novel applications ranging from narrow-linewidth lasers, microwave photonics, to chip-scale optical frequency combs and quantum frequency conversion. To translate these results into a widespread technology, attaining ultralow optical losses with established foundry manufacturing is critical. Recent advances in fabrication of integrated Si3N4 photonics have shown that ultralow-loss, dispersion-engineered microresonators can be attained at die-level throughput. For emerging nonlinear applications such as integrated travelling-wave parametric amplifiers and mode-locked lasers, PICs of length scales of up to a meter are required, placing stringent demands on yield and performance that have not been met with current fabrication techniques. Here we overcome these challenges and demonstrate a fabrication technology which meets all these requirements on wafer-level yield, performance and length scale. Photonic microresonators with a mean Q factor exceeding 30 million, corresponding to a linear propagation loss of 1.0 dB/m, are obtained over full 4-inch wafers, as determined from a statistical analysis of tens of thousands of optical resonances and cavity ringdown with 19 ns photon storage time. The process operates over large areas with high yield, enabling 1-meter-long spiral waveguides with 2.4 dB/m loss in dies of only 5x5 mm size. Using a modulation response measurement self-calibrated via the Kerr nonlinearity, we reveal that, strikingly, the intrinsic absorption-limited Q factor of our Si3N4 microresonators exceeds a billion. Transferring the present Si3N4 photonics technology to standard commercial foundries, and merging it with silicon photonics using heterogeneous integration technology, will significantly expand the scope of today's integrated photonics and seed new applications.

physics.app-ph↗