arXiv subjects

Dalziel J. Wilson

Publications and source records attributed to Dalziel J. Wilson.

At least 19 recordsLinked to original sources

arXiv2026

Multimode radiation pressure actuation of a mechanical resonator using a spatial mode sorter

Multimode optomechanical scattering is ubiquitous in free-space imaging protocols, but its radiation pressure counterpart is challenging to detect with extended objects. Here we demonstrate radiation pressure actuation of a nanomechanical membrane using dynamically structured light from a spatial mode demultiplexer (SPADE). Using single- and two-mode illumination, we directly image the position-dependent intermodal coupling between Hermite-Gauss (HG) modes as mediated by the membrane's motion. As an application, we use multimode radiation pressure feedback to simultaneously cool two nearly degenerate membrane modes. Our results are applicable to diverse mechanical systems and serve as a stepping stone to SPADE-based quantum optomechanics.

physics.optics↗

arXiv2026

Angular displacement readout of a mechanical oscillator with a guided mode resonance

Measuring the angular displacement of a mechanical oscillator is a ubiquitous task; however, the multimode nature of angular optomechanical coupling makes coherent signal enhancement challenging. Here we demonstrate coherently enhanced angular displacement readout with an integrated guided mode resonance (GMR) structure, applying it to precision readout of a nanomechanical oscillator. Specifically, we fabricate subwavelength gratings into 100-nm-thick Si$_3$N$_4$ membranes and record their vibration by direct transmission measurements. The narrow linewidth $\approx 2.5\;\text{mrad}$ of the GMR enables a shot-noise-limited displacement imprecision of $ 10^{-9}\;\text{rad}/\sqrt{\text{Hz}}$ with nanowatts of optical power, sufficient to resolve the thermal motion of a $Q\approx 10^6$ torsion mode with a signal-to-noise ratio of 47 dB. Control experiments based on polarization and wavelength detuning confirm that the measured signal arises from GMR-mediated transduction. These results establish guided-mode resonance as an on-chip approach to angular displacement readout in quantum optomechanical sensors.

physics.optics↗

arXiv2026

Dual mass milligram-scale torsion oscillator for vibration-free optomechanical sensing

Chip-scale optomechanical devices are driving the miniaturization of inertial sensors and next generation fundamental physics experiments. However, precision at the theoretical limit is often unattainable due to extraneous vibrations. One solution is tailoring the device to isolate a degree of freedom from the environment while maintaining coupling to the signal of interest. To this end, we introduce a dual milligram-mass torsion oscillator, formed by mass loading a strained silicon nitride nanoribbon. The antisymmetric torsion mode suppresses vibrations by over an order of magnitude to achieve a thermally limited torque sensitivity of $10^{-18}$ Nm/$\sqrt{\rm Hz}$ while maintaining ultralow loss. We demonstrate the sensing ability by detecting an optical radiation pressure torque of $10^{-16}$ Nm over a 30 Hz bandwidth. We also characterize the device for frequency-based gravimetry, demonstrating $10^{-6}g_0$ ($g_0=9.8$ $\rm m s^{-2}$) precision in 30 seconds with an oscillation amplitude of only 100 $μ$rad. This device demonstrates a technique for overcoming vibration noise, with broad implications for optomechanical sensing from commercial applications to fundamental physics experiments.

physics.app-ph↗

arXiv2026

Sail membranes for optomechanical accelerometry

Strained membrane resonators have emerged as a promising platform for optomechanical accelerometry; however, the desired combination of low frequency and high $Q$-mass product requires a rethinking of their dissipation dilution engineering. Applying Bayesian optimization to a Si$_3$N$_4$ membrane, we discover a class of sail-like trampoline resonators in which the frequency is decreased by an order of magnitude while preserving the $Q$-mass product. We demonstrate centimeter-scale sails with kHz frequencies, $Q\sim10^7$ and $Q\times\text{mass}\sim$ 10 g. Vertically integrating a 7 kHz device with a nanoribbon, we realize a monolithic cavity optomechanical accelerometer with a room temperature thermal noise of $40\;\text{n}g_0/\sqrt{\text{Hz}}$, sufficient to resolve $μg_0/\sqrt{\text{Hz}}$ ambient vibration over a bandwidth of 4 kHz with a displacement imprecision of $10^{-14}\;\text{m}/\sqrt{\text{Hz}}$. Cryogenic arrays of sail membranes may be attractive for new physics searches and distributed quantum sensing experiments.

quant-ph↗

arXiv2026

Nanofabricated torsion pendulums for tabletop gravity experiments

Measurement of mutual gravitation on laboratory scales is an outstanding challenge and a prerequisite to probing theories of quantum gravity. A leading technology in tabletop gravity experiments is the torsion balance, with limitations due to thermal decoherence. Recent demonstrations of lithographically defined suspensions in thin-film silicon nitride with macroscale test masses suggest a path forward, as torsion pendulums dominated by gravitational stiffness may achieve higher mechanical quality factors through dilution of material losses. Here we demonstrate a 250 micron by 5 mm by 1.8 micron torsion fiber supporting 87 grams and forming a Cavendish-style torsion pendulum with tungsten test masses that -- to our knowledge -- is the largest thin-film silicon-nitride-based oscillator to date. Torsion pendulums with thin-film, nanofabricated suspensions provide a test bed for near-term tabletop experiments probing classical and quantum gravitational interaction between oscillators.

physics.ins-det↗

arXiv2025

Lithographically Defined Si$_3$N$_4$ Torsional Pendulum

Torsion pendulums provide an opportunity to trap large masses in a potential weak enough to explore two-body gravitation. Cooled to, and then released from a ground state, weak quantum effects, including those from gravity, might reveal themselves in the evolving decoherence of a torsion pendulum, if its baseline dissipation were sufficiently dilute for quantum coherent oscillation. Monolithic ribbon-like, or multi-filar suspension geometries provide a key to such dilution in torsion, but are challenging to make. As a solution, we introduce a lithographically defined silicon nitride (Si$_3$N$_4$) ribbon suspension in a wafer-scale approach to pendulum fabrication that is conducive to such 2-D geometries, making extreme aspect ratios, and even multi-filar designs, a possibility. A monofilar, monolithic, centimeter scale torsion pendulum is fabricated and released in a first proof of concept. Mounted in vacuum, it is optically excited and cooled using measurement based feedback. Though only 37 mg, the device displays a fundamental frequency of 162 mHz and an undiluted Q of 12000, demonstrating a foundational step towards ultra-coherent, ultra-low frequency torsion pendulums.

physics.app-ph↗

arXiv2025

Fabrication and characterization of high-Q silicon nitride membrane resonators

Silicon nitride membranes are a powerful and ubiquitous optomechanical resonator technology, enabling high mechanical Q, low optical loss, and enhanced optomechanical coupling via a panoply of strain-, phononic-, and photonic-crystal engineering techniques. Fabrication and characterization of silicon nitride membranes has become a form of tacit knowledge in optomechanics research groups. Here we present a video run-through of the design, fabrication, and characterization of a contemporary silicon nitride membrane resonator (specifically, a centimeter-scale Si3N4 nanoribbon supporting $Q>10^8$ torsion modes). Our tutorial can serve as a starting point or refresher for practitioners in the field.

cond-mat.mes-hall↗

arXiv2025

Optimal single-mode squeezing for beam displacement sensing

Estimation of an optical beam's transverse displacement is a canonical imaging problem fundamental to numerous optical imaging and sensing tasks. Quantum enhancements to the measurement precision in this problem have been studied extensively. However, previous studies have neither accounted for diffraction loss in full generality, nor have they addressed how to jointly optimize the spatial mode and the balance between squeezing and coherent amplitude. Here we show that, in the small-displacement limit, the seemingly intractable infinite-spatial-mode problem can be reduced to a compact three-mode interaction framework. We quantify the improvement afforded by an optimized single-spatial-mode Gaussian-state probe over the optimal classical laser probe, and show that a two-spatial-mode homodyne receiver is asymptotically optimal for the former in the limit of high probe energy. Our findings reveal a strategy for identifying quantum-optimal probes in the presence of generic multimode linear probe-target interaction and photon loss.

quant-ph↗

arXiv2025

Imaging-based Quantum Optomechanics

In active imaging protocols, information about an object is encoded into the spatial mode of a scattered photon. Recently the quantum limits of active imaging have been explored with levitated nanoparticles, which experience a multimode radiation pressure backaction (the photon recoil force) due to radiative scattering of the probe field. Here we extend the analysis of multimode backaction to compliant surfaces, accessing a broad class of mechanical resonators and fruitful analogies to quantum imaging. As an example, we consider imaging of the flexural modes of a membrane by sorting the spatial modes of a laser reflected from its surface. We show that backaction in this setting can be understood to arise from spatiotemporal photon shot noise, an effect that cannot be observed in single-mode optomechanics. We also derive the imprecision-backaction product in the limit of purely spatial (intermodal) coupling, revealing it to be equivalent to the standard quantum limit for single-mode optomechanical coupling. Finally, we show that optomechanical correlations due to spatiotemporal backaction can give rise to two-mode entangled light, providing a mechanism for entangling desired pairs of spatial modes. In conjunction with high-Q nanomechanics, our findings point to new opportunities at the interface of quantum imaging and optomechanics, including sensors and networks enhanced by spatial mode entanglement.

quant-ph↗

arXiv2025

Ultrahigh-Q Torsional Nanomechanics through Bayesian Optimization

Recently it was discovered that torsion modes of strained nanoribbons exhibit dissipation dilution, giving a route to enhanced torque sensing and quantum optomechanics experiments. As with all strained nanomechanical resonators, an important limitation is bending loss due to mode curvature at the clamps. Here we use Bayesian optimization to design nanoribbons with optimal dissipation dilution of the fundamental torsion mode. Applied to centimeter-scale Si$_3$N$_4$ nanoribbons, we realize $Q$ factors exceeding 100 million and $Q$-frequency products exceeding $10^{13}$ Hz at room temperature. The thermal torque sensitivity of the reported devices is at the level of $10^{-20}\;\text{N}\,\text{m}/\sqrt{\text{Hz}}$ and the zero point angular displacement spectral density is at the level of $10^{-10}\;\text{rad}/\sqrt{\text{Hz}}$; they are moreover simple to fabricate, have high thermal conductivity, and can be heavily mass-loaded without diminishing their $Q$, making them attractive for diverse fundamental and applied weak force sensing tasks.

cond-mat.mes-hall↗

arXiv2024

Quantum-limited optical lever measurement of a torsion oscillator

The optical lever is a precision displacement sensor with broad applications. In principle, it can track the motion of a mechanical oscillator with added noise at the Standard Quantum Limit (SQL); however, demonstrating this performance requires an oscillator with an exceptionally high torque sensitivity, or, equivalently, zero-point angular displacement spectral density. Here, we describe optical lever measurements on Si$_3$N$_4$ nanoribbons possessing $Q>3\times 10^7$ torsion modes with torque sensitivities of $10^{-20}\,\text{N m}/\sqrt{\text{Hz}}$ and zero-point displacement spectral densities of $10^{-10}\,\text{rad}/\sqrt{\text{Hz}}$. Compensating aberrations and leveraging immunity to classical intensity noise, we realize angular displacement measurements with imprecisions 20 dB below the SQL and demonstrate feedback cooling, using a position modulated laser beam as a torque actuator, from room temperature to $\sim5000$ phonons. Our study signals the potential for a new class of torsional quantum optomechanics.

quant-ph↗

arXiv2024

Optimum classical beam position sensing

Beam displacement measurements are widely used in optical sensing and communications; however, their performance is affected by numerous intrinsic and extrinsic factors including beam profile, propagation loss, and receiver architecture. Here we present a framework for designing a classically optimal beam displacement transceiver, using quantum estimation theory. We consider the canonical task of estimating the position of a diffraction-limited laser beam after passing through an apertured volume characterized by Fresnel-number product DF. As a rule of thumb, higher-order Gaussian modes provide more information about beam displacement, but are more sensitive to loss. Applying quantum Fisher information, we design mode combinations that optimally leverage this trade-off, and show that a greater than 10-fold improvement in precision is possible, relative to the fundamental mode, for a practically relevant DF = 100. We also show that this improvement is realizable with a variety of practical receiver architectures. Our findings extend previous works on lossless transceivers, may have immediate impact on applications such as atomic force microscopy and near-field optical communication, and pave the way towards globally optimal transceivers using non-classical laser fields.

physics.optics↗

arXiv2023

Sub-ppm Nanomechanical Absorption Spectroscopy of Silicon Nitride

Material absorption is a key limitation in nanophotonic systems; however, its characterization is often obscured by scattering and diffraction loss. Here we show that nanomechanical frequency spectroscopy can be used to characterize the absorption of a dielectric thin film at the parts-per-million (ppm) level, and use it to characterize the absorption of stoichiometric silicon nitride (Si$_3$N$_4$), a ubiquitous low-loss optomechanical material. Specifically, we track the frequency shift of a high-$Q$ Si$_3$N$_4$ trampoline resonator in response to photothermal heating by a $\sim10$ mW laser beam, and infer the absorption of the thin film from a model including thermal stress relaxation and both radiative and conductive heat transfer. A key insight is the presence of two thermalization timescales, a rapid ($\sim0.1$ sec) timescale due to radiative thermalization of the Si$_3$N$_4$ thin film, and a slow ($\sim100$ sec) timescale due to parasitic heating of the Si device chip. We infer the extinction coefficient of Si$_3$N$_4$ to be $\sim0.1-1$ ppm in the 532 - 1550 nm wavelength range, comparable to bounds set by waveguide resonators and notably lower than estimates with membrane-in-the-middle cavity optomechanical systems. Our approach is applicable to a broad variety of nanophotonic materials and may offer new insights into their potential.

physics.optics↗

arXiv2023

Thermal intermodulation backaction in a high-cooperativity optomechanical system

The pursuit of room temperature quantum optomechanics with tethered nanomechanical resonators faces stringent challenges owing to extraneous mechanical degrees of freedom. An important example is thermal intermodulation noise (TIN), a form of excess optical noise produced by mixing of thermal noise peaks. While TIN can be decoupled from the phase of the optical field, it remains indirectly coupled via radiation pressure, implying a hidden source of backaction that might overwhelm shot noise. Here we report observation of TIN backaction in a high-cooperativity, room temperature cavity optomechanical system consisting of an acoustic-frequency Si$_3$N$_4$ trampoline coupled to a Fabry-Pérot cavity. The backaction we observe exceeds thermal noise by 20 dB and radiation pressure shot noise by 40 dB, despite the thermal motion being 10 times smaller than the cavity linewidth. Our results suggest that mitigating TIN may be critical to reaching the quantum regime from room temperature in a variety of contemporary optomechanical systems.

quant-ph↗

arXiv2022

Entanglement-enhanced optomechanical sensor array for dark matter searches

The nature of dark matter is one of the most important open questions in modern physics. The search for dark matter is challenging since, besides gravitational interaction, it feebly interacts with ordinary matter. Mechanical sensors are one of the leading candidates for dark matter searches in the low frequency region. Here, we propose entanglement-enhanced optomechanical sensing systems to assist the search for DM with mechanical sensing devices. To assess the performance of our setup, we adopt the integrated sensitivity, which is particularly suitable for broadband sensing as it precisely quantifies the bandwidth-sensitivity tradeoff of the system. We then show that, by coherently operating the optomechanical sensor array and utilizing continuous-variable multi-partite entanglement between the optical fields, the array of sensors has a scaling advantage over independent sensors (i.e., $\sqrt{M}\rightarrow M$, where $M$ is the number of sensors) as well as a performance boost due to entanglement. Such an advantage is robust to imhomogeneities of the mechanical sensors and is achievable with off-the-shelf experimental components.

quant-ph↗

arXiv2022

Entanglement-Enhanced Optomechanical Sensing

Optomechanical systems have been exploited in ultrasensitive measurements of force, acceleration, and magnetic fields. The fundamental limits for optomechanical sensing have been extensively studied and now well understood -- the intrinsic uncertainties of the bosonic optical and mechanical modes, together with the backaction noise arising from the interactions between the two, dictate the Standard Quantum Limit (SQL). Advanced techniques based on nonclassical probes, in-situ pondermotive squeezed light, and backaction-evading measurements have been developed to overcome the SQL for individual optomechanical sensors. An alternative, conceptually simpler approach to enhance optomechanical sensing rests upon joint measurements taken by multiple sensors. In this configuration, a pathway toward overcoming the fundamental limits in joint measurements has not been explored. Here, we demonstrate that joint force measurements taken with entangled probes on multiple optomechanical sensors can improve the bandwidth in the thermal-noise-dominant regime or the sensitivity in shot-noise-dominant regime. Moreover, we quantify the overall performance of entangled probes with the sensitivity-bandwidth product and observe a 25% increase compared to that of the classical probes. The demonstrated entanglement-enhanced optomechanical sensing could enable new capabilities for inertial navigation, acoustic imaging, and searches for new physics.

quant-ph↗

arXiv2022

Membrane-based Optomechanical Accelerometry

Optomechanical accelerometers promise quantum-limited readout, high detection bandwidth, self-calibration, and radiation pressure stabilization. We present a simple, scalable platform that enables these benefits with nano-$g$ sensitivity at acoustic frequencies, based on a pair of vertically integrated Si$_3$N$_4$ membranes with different stiffnesses, forming an optical cavity. As a demonstration, we integrate an ultrahigh-Q ($>10^7$), millimeter-scale Si$_3$N$_4$ trampoline membrane above an unpatterned membrane on the same Si chip, forming a finesse $\mathcal{F}\approx2$ cavity. Using direct photodetection in transmission, we resolve the relative displacement of the membranes with a shot-noise-limited imprecision of 7 fm/$\sqrt{\text{Hz}}$, yielding a thermal-noise-limited acceleration sensitivity of 562 n$g/\sqrt{\text{Hz}}$ over a 1 kHz bandwidth centered on the fundamental trampoline resonance (40 kHz). To illustrate the advantage of radiation pressure stabilization, we cold damp the trampoline to an effective temperature of 4 mK and leverage the reduced energy variance to resolve an applied stochastic acceleration of 50 n$g/\sqrt{\text{Hz}}$ in an integration time of minutes. In the future, we envision a small-scale array of these devices operating in a cryostat to search for fundamental weak forces such as dark matter.

cond-mat.mes-hall↗

arXiv2021

Nanoscale torsional dissipation dilution for quantum experiments and precision measurement

We show that torsion resonators can experience massive dissipation dilution due to nanoscale strain, and draw a connection to a century-old theory from the torsion balance community which suggests that a simple torsion ribbon is naturally soft-clamped. By disrupting a commonly held belief in the nanomechanics community, our findings invite a rethinking of strategies towards quantum experiments and precision measurement with nanomechanical resonators. For example, we revisit the optical lever technique for monitoring displacement, and find that the rotation of a strained nanobeam can be resolved with an imprecision smaller than the zero-point motion of its fundamental torsional mode, without the use of a cavity or interferometric stability. We also find that a strained torsion ribbon can be mass-loaded without changing its $Q$ factor. We use this strategy to engineer a chip-scale torsion balance whose resonance frequency is sensitive to micro-$g$ fluctuations of the local gravitational field. Enabling both these advances is the fabrication of high-stress Si$_3$N$_4$ nanobeams with width-to-thickness ratios of $10^4$ and the recognition that their torsional modes have $Q$ factors scaling as their width-to-thickness ratio squared, yielding $Q$ factors as high as $10^8$ and $Q$-frequency products as high as $10^{13}$ Hz.

cond-mat.mes-hall↗