Feedback Enhanced Sensitivity in Optomechanics: Surpassing the Parametric Instability Barrier

The intracavity power, and hence sensitivity, of optomechanical sensors is commonly limited by parametric instability. Here we characterize the parametric instability induced sensitivity degradation in a micron scale cavity optomechanical system. Feedback via optomechanical transduction and electrical gradient force actuation is applied to suppress the parametric instability. As a result a 5.4 fold increase in mechanical motion transduction sensitivity is achieved to a final value of $1.9\times 10^{-18}\rm m Hz^{-1/2}$.Comment: 4 pages, 4 figure

On the transduction of various noise sources in optical microtoroids

Optical microresonators constitute the basic building block for numerous precision measurements including single-particle detection, magnetometry, force and position sensing. The ability to resolve a signal of interest is limited however by various noise sources. In this tutorial style paper we provide a matrix formalism to analyze the effect of various modulations upon the optical cavity. The technique can in principle be used to estimate the sensitivity of microresonator based sensors and potentially to identify the optimal detection basis and cavity parameters to optimise the signal to noise ratio

Cavity optoelectromechanical regenerative amplification

Cavity optoelectromechanical regenerative amplification is demonstrated. An optical cavity enhances mechanical transduction, allowing sensitive measurement even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was linewidth narrowed to 6.6\pm1.4 mHz, 30 times smaller than previously achieved with radiation pressure driving in such a system. These results may have applications in areas such as ultrasensitive optomechanical mass spectroscopy

Adaptation to transboundary climate risks in trade: investigating actors and strategies for an emerging challenge

There is growing recognition that international trade can transmit climate risks across borders, requiring new forms of and approaches to adaptation. This advanced review synthesizes knowledge on how, by whom and where adaptation actions can be taken in the agriculture and industrial sectors to reduce these transboundary climate risks (TCRs). We find a material difference in the literature on TCRs in agriculture as compared with industrial sectors. Operational and market risks, in particular reductions in food availability, dominate in agriculture, while supply chain and trade-related risks are highlighted for industry. While the origin of the risk (source) is the primary target of adaptation to agricultural TCRs, the general governance structure, such as UNFCCC and WTO deliberations, are important targets in both sectors. Adaptation at the country of destination and along the trade network is of minor importance in both sectors. Regarding the type of adaptation option, agriculture heavily relies on trade policy, agricultural adaptation, and adaptation planning and coordination, while in industry knowledge creation, research and development, and risk management are seen as essential. Governments and the international community are identified as key actors, complemented by businesses and research as critical players in industry. Some measures, such as protectionist trade policies and irrigation, are controversial as they shift risks across countries and sectors, rather than reduce them. While more research is needed, this review shows that a critical mass of evidence on adaptation to TCRs is beginning to emerge, particularly underscoring the importance of international coordination mechanisms. This article is categorized under:. Vulnerability and Adaptation to Climate Change > Institutions for Adaptation Vulnerability and Adaptation to Climate Change > Multilevel and Transnational Climate Change Governance

Interferometric detection of mode splitting for whispering gallery mode biosensors

Sensors based on whispering gallery mode resonators can detect single nanoparticles and even single molecules. Particles attaching to the resonator induce a doublet in the transmission spectrum which provides a self-referenced detection signal. However, in practice this spectral feature is often obscured by the width of the resonance line which hides the doublet structure. This happens particularly in liquid environments that reduce the effective Q factor of the resonator. In this paper we demonstrate an interferometric set-up that allows the direct detection of the hidden doublet and thus provides a pathway for developing practical sensor applications.Comment: 9 page

Fundamental constraints on particle tracking with optical tweezers

A general quantum limit to the sensitivity of particle position measurements is derived following the simple principle of the Heisenberg microscope. The value of this limit is calculated for particles in the Rayleigh and Mie scattering regimes, and with parameters which are relevant to optical tweezers experiments. The minimum power required to observe the zero-point motion of a levitating bead is also calculated, with the optimal particle diameter always smaller than the wavelength. We show that recent optical tweezers experiments are within two orders of magnitude of quantum limited sensitivity, suggesting that quantum optical resources may soon play an important role in high sensitivity tracking applications

Subdiffraction-Limited Quantum Imaging within a Living Cell

We report both subdiffraction-limited quantum metrology and quantum-enhanced spatial resolution for the first time in a biological context. Nanoparticles are tracked with quantum-correlated light as they diffuse through an extended region of a living cell in a quantum-enhanced photonic-force microscope. This allows spatial structure within the cell to be mapped at length scales down to 10 nm. Control experiments in water show a 14% resolution enhancement compared to experiments with coherent light. Our results confirm the long-standing prediction that quantum-correlated light can enhance spatial resolution at the nanoscale and in biology. Combined with state-of-the-art quantum light sources, this technique provides a path towards an order of magnitude improvement in resolution over similar classical imaging techniques

Electron-Phonon interaction and electronic decoherence in molecular conductors

We perform a brief but critical review of the Landauer picture of transport that clarifies how decoherence appears in this approach. On this basis, we present different models that allow the study of the coherent and decoherent effects of the interaction with the environment in the electronic transport. These models are particularly well suited for the analysis of transport in molecular wires. The effects of decoherence are described through the D'Amato-Pastawski model that is explained in detail. We also consider the formation of polarons in some models for the electron-vibrational interaction. Our quantum coherent framework allows us to study many-body interference effects. Particular emphasis is given to the occurrence of anti-resonances as a result of these interferences. By studying the phase fluctuations in these soluble models we are able to identify inelastic and decoherence effects. A brief description of a general formulation for the consideration of time-dependent transport is also presented.Comment: 32 pages, 11 eps figures. To appear in Chemical Physics (Special Molecular Electronics Number

Biological measurement beyond the quantum limit

Quantum noise places a fundamental limit on the per photon sensitivity attainable in optical measurements. This limit is of particular importance in biological measurements, where the optical power must be constrained to avoid damage to the specimen. By using non-classically correlated light, we demonstrated that the quantum limit can be surpassed in biological measurements. Quantum enhanced microrheology was performed within yeast cells by tracking naturally occurring lipid granules with sensitivity 2.4 dB beyond the quantum noise limit. The viscoelastic properties of the cytoplasm could thereby be determined with a 64% improved measurement rate. This demonstration paves the way to apply quantum resources broadly in a biological context