arXiv subjects

Warwick P. Bowen

Publications and source records attributed to Warwick P. Bowen.

At least 37 records · Page 2Linked to original sources

arXiv2024

Enhancement of mechanical squeezing via feedback control

We explore the generation of nonclassical mechanical states by combining continuous position measurement and feedback control. We find that feedback-induced spring softening can greatly enhance position squeezing. Conversely, even with a pure position measurement, we find that spring hardening can enable momentum squeezing. Beyond enhanced squeezing, we show that feedback also mitigates degradation introduced by background mechanical modes. Together, this significantly lowers the barrier to measurement-based preparation of nonclassical mechanical states at room temperature.

quant-ph↗

arXiv2023

Emergent Error Correcting States in Networks of Nonlinear Oscillators

Networks of nonlinear oscillators can exhibit complex collective behaviour ranging from synchronised states to chaos. Here, we simulate the dynamics of three coupled Duffing oscillators whose multiple equilibrium states can be used for information processing and storage. Our analysis reveals that even for this small network, there is the emergence of an error correcting phase where the system autonomously corrects errors from random impulses. The system has several surprising and attractive features, including dynamic isolation of resonators exposed to extreme impulses and the ability to correct simultaneous errors. The existence of an error correcting phase opens the prospect of fault-tolerant information storage, with particular applications in nanomechanical computing.

physics.class-ph↗

arXiv2023

Quantitative Profilometric Measurement of Magnetostriction in Thin-Films

A DC non-contact method for measuring the magnetostrictive strain in thin-films is demonstrated, achieving a state-of-the-art sensitivity of 0.1 ppm. In this method, an optical profilometer is used to measure the curvature induced in a magnetostrictively coated coverslip under a DC field through phase-sensitive interferometry. From this the magnetostrictive stress and strain are calculated using Stoney's formula. This addresses limitations of conventional techniques that measure magnetostriction based on the deflection of a cantilever under an AC field, which require complex dedicated set-ups and are sensitive to vibrational noise. Further, it reveals information about the anisotropy of the film and allows for the possibility of measuring multiple samples simultaneously. The theoretical sensitivity limits are derived, predicting a shot-noise-limit of 0.01 ppm. The method is implemented to measure the magnetostrictive hysteresis and piezomagnetic coupling of thin-film galfenol. Degradation in film performance is observed above a thickness of 206 nm, alongside a change in coercivity. This prompts investigation into the growth and optimization of galfenol films for use in devices.

physics.app-ph↗

arXiv2023

Waveguide-integrated and portable optomechanical magnetometer

Optomechanical magnetometers enable highly sensitive magnetic field sensing. However, all such magnetometers to date have been optically excited and read-out either via free space or a tapered optical fiber. This limits their scalability and integrability, and ultimately their range of applications. Here, we present an optomechanical magnetometer that is excited and read out via a suspended optical waveguide fabricated on the same silicon chip as the magnetometer. Moreover, we demonstrate that thermomechanical noise limited sensitivity is possible using portable electronics and laser. The magnetometer employs a silica microdisk resonator selectively sputtered with a magnetostrictive film of galfenol (FeGa) which induces a resonant frequency shift in response to an external magnetic field. Experimental results reveal the retention of high quality-factor optical whispering gallery mode resonances whilst also demonstrating high sensitivity and dynamic range in ambient conditions. The use of off-the-shelf portable electronics without compromising sensor performance demonstrates promise for applications.

physics.optics↗

arXiv2023

Continuous optical-to-mechanical quantum state transfer in the unresolved sideband regime

Optical-to-mechanical quantum state transfer is an important capability for future quantum networks, quantum communication, and distributed quantum sensing. However, existing continuous state transfer protocols operate in the resolved sideband regime, necessitating a high-quality optical cavity and a high mechanical resonance frequency. Here, we propose a continuous protocol that operates in the unresolved sideband regime. The protocol is based on feedback cooling, can be implemented with current technology, and is able to transfer non-Gaussian quantum states with high fidelity. Our protocol significantly expands the kinds of optomechanical devices for which continuous optical-to-mechanical state transfer is possible, paving the way towards quantum technological applications and the preparation of macroscopic superpositions to test the fundamentals of quantum science.

quant-ph↗

arXiv2022

Engineered entropic forces allow ultrastrong dynamical backaction

When confined within an optical cavity, light can exert strong radiation pressure forces. Combined with dynamical backaction, this enables important processes such as laser cooling, and applications ranging from precision sensors to quantum memories and interfaces. However, the magnitude of radiation pressure forces is constrained by the energy mismatch between photons and phonons. Here, we overcome this barrier using entropic forces arising from the absorption of light. We show that entropic forces can exceed the radiation pressure force by eight orders of magnitude, and demonstrate this using a superfluid helium third-sound resonator. We develop a framework to engineer the dynamical backaction from entropic forces, applying it to achieve phonon lasing with a threshold three orders of magnitude lower than previous work. Our results present a pathway to exploit entropic forces in quantum devices, and to study nonlinear fluid phenomena such as turbulence and solitons.

physics.optics↗

arXiv2022

Testing spontaneous wavefunction collapse with quantum electromechanics

Theories of spontaneous wavefunction collapse offer an explanation of the possible breakdown of quantum mechanics for macroscopic systems. However, the challenge of resolving predicted collapse signatures above background noise has precluded conclusive tests. Here, we propose to overcome this challenge using a superconducting qubit to precisely readout the collapse-induced heating of a mechanical resonator. We show that the ability to strongly couple the qubit to the resonator can enable both fast measurements and initialization of the qubit close to its ground state. Combined this greatly suppresses the influence of quasiparticle heating of the qubit, which we predict to be the dominant noise source. We find that bulk acoustic wave resonances can amplify the collapse induced heating due to their ultra-low dissipation. Together, this could enable a conclusive test of collapse models.

quant-ph↗

arXiv2022

Scalable nanomechanical logic gate

Nanomechanical computers promise robust, low energy information processing. However, to date, electronics have generally been required to interconnect gates, while no scalable, purely nanomechanical approach to computing has been achieved. Here, we demonstrate a nanomechanical logic gate in a scalable architecture. Our gate uses the bistability of a nonlinear mechanical resonator to define logical states. These states are efficiently coupled into and out of the gate via nanomechanical waveguides, which provide the mechanical equivalent of electrical wires. Crucially, the input and output states share the same spatiotemporal characteristics, so that the output of one gate can serve as the input for the next. Our architecture is CMOS compatible, while realistic miniaturisation could allow both gigahertz frequencies and an energy cost that approaches the fundamental Landauer limit. Together this presents a pathway towards large-scale nanomechanical computers, as well as neuromorphic networks able to simulate computationally hard problems and interacting many-body systems.

cond-mat.mes-hall↗

arXiv2021

Quantum Biotechnology

Quantum technologies leverage the laws of quantum physics to achieve performance advantages in applications ranging from computing to communications and sensing. They have been proposed to have a range of applications in biological science. This includes better microscopes and biosensors, improved simulations of molecular processes, and new capabilities to control the behaviour of biomolecules and chemical reactions. Quantum effects are also predicted, with much debate, to have functional benefits in biology, for instance, allowing more efficient energy transport and improving the rate of enzyme catalysis. Conversely, the robustness of biological systems to disorder from their environment has led to proposals to use them as components within quantum technologies, for instance as light sources for quantum communication systems. Together, this breadth of prospective applications at the interface of quantum and biological science suggests that quantum physics will play an important role in stimulating future biotechnological advances. This review aims to provide an overview of this emerging field of quantum biotechnology, introducing current capabilities, future prospects, and potential areas of impact. The review is written to be accessible to the non-expert and focuses on the four key areas of quantum-enabled sensing, quantum-enabled imaging, quantum biomolecular control, and quantum effects in biology.

quant-ph↗

arXiv2021

Measurement-based preparation of non-Markovian and multimode mechanical states

Nanomechanical resonators are a key tool for future quantum technologies such as quantum force sensors and interfaces, and for studies of macroscopic quantum physics. The ability to prepare room temperature non-classical states is a major outstanding challenge. Here, we explore the use of measurement-based state conditioning to achieve this. We demonstrate conditional cooling of a nanomechanical resonator that has non-Markovian decoherence, and show theoretically that the non-Markovianity makes quantum squeezing significantly easier to achieve. We further show that collective measurement of multiple resonator modes improves the quality of state preparation. This allows us to achieve collective thermomechanical squeezing, in experiments that go beyond the validity of the rotating-wave approximation. Our modelling shows that non-Markovianity and multimode conditioning can both enable room temperature quantum squeezing with existing technology. Together, our results pave the way towards realising room temperature quantum nanomechanical devices and towards their application in quantum technology and fundamental science.

quant-ph↗

arXiv2021

Dynamic polarizability of macromolecules for single-molecule optical biosensing

The structural dynamics of macromolecules is important for most microbiological processes, from protein folding to the origins of neurodegenerative disorders. Noninvasive measurements of these dynamics are highly challenging. Recently, optical sensors have been shown to allow noninvasive time-resolved measurements of the dynamic polarizability of single-molecules. Here we introduce a method to efficiently predict the dynamic polarizability from the atomic configuration of a given macromolecule. This provides a means to connect the measured dynamic polarizability to the underlying structure of the molecule, and therefore to connect temporal measurements to structural dynamics. To illustrate the methodology we calculate the change in polarizability as a function of time based on conformations extracted from molecular dynamics simulations and using different conformations of motor proteins solved crystalographically. This allows us to quantify the magnitude of the changes in polarizablity due to thermal and functional motions.

physics.bio-ph↗

arXiv2021

Precision Magnetometers for Aerospace Applications

Aerospace technologies are crucial for modern civilization; space-based infrastructure underpins weather forecasting, communications, terrestrial navigation and logistics, planetary observations, solar monitoring, and other indispensable capabilities. Extraplanetary exploration -- including orbital surveys and (more recently) roving, flying, or submersible unmanned vehicles -- is also a key scientific and technological frontier, believed by many to be paramount to the long-term survival and prosperity of humanity. All of these aerospace applications require reliable control of the craft and the ability to record high-precision measurements of physical quantities. Magnetometers deliver on both of these aspects, and have been vital to the success of numerous missions. In this review paper, we provide an introduction to the relevant instruments and their applications. We consider past and present magnetometers, their proven aerospace applications, and emerging uses. We then look to the future, reviewing recent progress in magnetometer technology. We particularly focus on magnetometers that use optical readout, including atomic magnetometers, magnetometers based on quantum defects in diamond, and optomechanical magnetometers. These optical magnetometers offer a combination of field sensitivity, size, weight, and power consumption that allows them to reach performance regimes that are inaccessible with existing techniques. This promises to enable new applications in areas ranging from unmanned vehicles to navigation and exploration.

physics.app-ph↗

arXiv2021

Nanomechanical Dissipation and Strain Engineering

Nanomechanical resonators have applications in a wide variety of technologies ranging from biochemical sensors to mobile communications, quantum computing, inertial sensing, and precision navigation. The quality factor of the mechanical resonance is critical for many applications. Until recently, mechanical quality factors rarely exceeded a million. In the past few years however, new methods have been developed to exceed this boundary. These methods involve careful engineering of the structure of the nanomechanical resonator, including the use of acoustic bandgaps and nested structures to suppress dissipation into the substrate, and the use of dissipation dilution and strain engineering to increase the mechanical frequency and suppress intrinsic dissipation. Together, they have allowed quality factors to reach values near a billion at room temperature, resulting in exceptionally low dissipation. This review aims to provide a pedagogical introduction to these new methods, primarily targeted to readers who are new to the field, together with an overview of the existing state-of-the-art, what may be possible in the future, and a perspective on the future applications of these extreme-high quality resonators.

physics.app-ph↗

arXiv2021

A computational tool to characterize particle tracking measurements in optical tweezers

Here we present a computational tool for optical tweezers which calculates the particle tracking signal measured with a quadrant detector and the shot-noise limit to position resolution. The tool is a piece of Matlab code which functions within the freely available Optical Tweezers Toolbox. It allows the measurements performed in most optical tweezers experiments to be theoretically characterized in a fast and easy manner. The code supports particles with arbitrary size, any optical fields and any combination of objective and condenser, and performs a full vector calculation of the relevant fields. Example calculations are presented which show the tracking signals for different particles, and the shot noise limit to position sensitivity as a function of the effective condenser NA.

physics.ins-det↗

arXiv2021

Quantum Enhanced Microrheology of a Living Cell

We demonstrate the first biological measurement with precision surpassing the quantum noise limit. Lipid particles within a living yeast cell are tracked with sub-shot noise sensitivity, thereby revealing the biological dynamics of the cellular cytoplasm.

quant-ph↗

arXiv2021

Ultrasensitive optical magnetometry at the microscale

Recent advances in optical magnetometry have achieved record sensitivity at both macro- and nano-scale. Combined with high bandwidth and non-cryogenic operation, this has enabled many applications. By comparison, microscale optical magnetometers have been constrained to sensitivities five orders-of-magnitude worse than the state-of-the-art. Here, we report an ambient optical micro-magnetometer operating for the first time in the picoTesla range, a more than three order-of-magnitude advance on previous results. Unlike other ultrasensitive optical magnetometers, the device operates at earth field, achieves tens of MHz bandwidth, and is integrated and fiber coupled. Combined with 60 micrometer spatial resolution and microWatt optical power requirements, these unique capabilities open up a broad range of applications including cryogen-free and microfluidic magnetic resonance imaging, and electromagnetic interference-free investigation of spin physics in condensed matter systems such as semiconductors and ultracold atom clouds

physics.optics↗

arXiv2021

Optically tunable photoluminescence and upconversion lasing on a chip

The ability to tune the wavelength of light emission on a silicon chip is important for scalable photonic networks, distributed photonic sensor networks and next generation computer architectures. Here we demonstrate light emission in a chip-scale optomechanical device, with wide tunablity provided by a combination of radiation pressure and photothermal effects. To achieve this, we develop an optically active double-disk optomechanical system through implantation of erbium ions. We observe frequency tuning of photoluminescence in the telecommunications band with a wavelength range of 520 pm, green upconversion lasing with a threshold of $340\pm 70 \; μ$W, and optomechanical self-pulsing caused by the interplay of radiation pressure and thermal effects. These results provide a path towards widely-tunable micron-scale lasers for photonic networks.

physics.optics↗

arXiv2021

Tunnelling of transverse acoustic waves on a silicon chip

Nanomechanical circuits for transverse acoustic waves promise to enable new approaches to computing, precision biochemical sensing and many other applications. However, progress is hampered by the lack of precise control of the coupling between nanomechanical elements. Here, we demonstrate virtual-phonon coupling between transverse mechanical elements, exploiting tunnelling through a zero-mode acoustic barrier. This allows the construction of large-scale nanomechanical circuits on a silicon chip, for which we develop a new scalable fabrication technique. As example applications, we build mode-selective acoustic mirrors with controllable reflectivity and demonstrate acoustic spatial mode filtering. Our work paves the way towards applications such as fully nanomechanical computer processors and distributed nanomechanical sensors, and to explore the rich landscape of nonlinear nanomechanical dynamics.

cond-mat.mes-hall↗