Detuned Mechanical Parametric Amplification as a Quantum Non-Demolition Measurement

Recently it has been demonstrated that the combination of weak-continuous position detection with detuned parametric driving can lead to significant steady-state mechanical squeezing, far beyond the 3 dB limit normally associated with parametric driving. In this work, we show the close connection between this detuned scheme and quantum non-demolition (QND) measurement of a single mechanical quadrature. In particular, we show that applying an experimentally realistic detuned parametric drive to a cavity optomechanical system allows one to effectively realize a QND measurement despite being in the bad-cavity limit. In the limit of strong squeezing, we show that this scheme offers significant advantages over standard backaction evasion, not only by allowing operation in the weak measurement and low efficiency regimes, but also in terms of the purity of the mechanical state.Comment: 17 pages, 2 figure

Mechanical Entanglement via Detuned Parametric Amplification

We propose two schemes to generate entanglement between a pair of mechanical oscillators using parametric amplification. In contrast to existing parametric drive-based protocols, both schemes operate in the steady-state. Using a detuned parametric drive to maintain equilibrium and to couple orthogonal quadratures, our approach can be viewed as a two-mode extension of previous proposals for parametric squeezing. We find that robust steady-state entanglement is possible for matched oscillators with well-controlled coupling. In addition, one of the proposed schemes is robust to differences in the damping rates of the two oscillators.Comment: 13 pages, 2 figure

An ‘equal effort’ approach to assessing the North–South climate finance gap

This study employs a number of Integrated Assessment Models to determine what the optimal financial transfers between high-income and developing economies would be if climate mitigation effort, measured as mitigation costs as a share of gross domestic product, were to be divided equally across regions through a global carbon market. We find these to be larger than both current and planned international climate finance flows. Four out of six models imply that a North–South annual financial transfer of around US$400 billion is required by 2050, while the other two models imply larger sums, up to$2 trillion. However, the outlook for multi-country carbon markets is not encouraging at the moment. We thus review some potential sources of funds that might be used to fill the climate finance gap, including public aid, private investment, development banks, and special climate-related facilities. We find the shortcomings of public climate finance appear particularly hard to overcome, and argue that expanding private finance, either in the form of Foreign Direct Investment or through the issuance of ‘green bonds’, appears to be a more promising direction. Policy relevance Climate change is a profoundly asymmetric development issue, as countries at lower stages of development are likely to suffer disproportionate climate damages and mitigation costs. High-income countries have agreed to mobilise $100 billion a year by 2020 ‘to address the needs of developing countries’. However, scaling up climate finance has been slow and, more importantly, targets have not been chosen on the basis of a ‘scientific’ assessment. This article presents a novel, model-based analysis of the ‘equal effort’ inter-regional climate finance that could provide useful insights to policy makers in future negotiations. The gap identified by comparing models’ projections to current and planned financial flows is large but not prohibitive. In particular, private investment appears to be the most likely channel to fill the gap, although various public policies need to be implemented to improve the risk/return profile of low-carbon investment opportunities

An ‘equal effort’ approach to assessing the North–South climate finance gap

This study employs a number of Integrated Assessment Models to determine what the optimal financial transfers between high-income and developing economies would be if climate mitigation effort, measured as mitigation costs as a share of gross domestic product, were to be divided equally across regions through a global carbon market. We find these to be larger than both current and planned international climate finance flows. Four out of six models imply that a North–South annual financial transfer of around US$400 billion is required by 2050, while the other two models imply larger sums, up to$2 trillion. However, the outlook for multi-country carbon markets is not encouraging at the moment. We thus review some potential sources of funds that might be used to fill the climate finance gap, including public aid, private investment, development banks, and special climate-related facilities. We find the shortcomings of public climate finance appear particularly hard to overcome, and argue that expanding private finance, either in the form of Foreign Direct Investment or through the issuance of ‘green bonds’, appears to be a more promising direction. Policy relevance Climate change is a profoundly asymmetric development issue, as countries at lower stages of development are likely to suffer disproportionate climate damages and mitigation costs. High-income countries have agreed to mobilise $100 billion a year by 2020 ‘to address the needs of developing countries’. However, scaling up climate finance has been slow and, more importantly, targets have not been chosen on the basis of a ‘scientific’ assessment. This article presents a novel, model-based analysis of the ‘equal effort’ inter-regional climate finance that could provide useful insights to policy makers in future negotiations. The gap identified by comparing models’ projections to current and planned financial flows is large but not prohibitive. In particular, private investment appears to be the most likely channel to fill the gap, although various public policies need to be implemented to improve the risk/return profile of low-carbon investment opportunities

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

Silsesquioxane polymer as a potential scaffold for laryngeal reconstruction

Cancer, disease and trauma to the larynx and their treatment can lead to permanent loss of structures critical to voice, breathing and swallowing. Engineered partial or total laryngeal replacements would need to match the ambitious specifications of replicating functionality, outer biocompatibility, and permissiveness for an inner mucosal lining. Here we present porous polyhedral oligomeric silsesquioxane-poly(carbonate urea) urethane (POSS-PCUU) as a potential scaffold for engineering laryngeal tissue. Specifically, we employ a precipitation and porogen leaching technique for manufacturing the polymer. The polymer is chemically consistent across all sample types and produces a foam-like scaffold with two distinct topographies and an internal structure composed of nano- and micro-pores. Whilst the highly porous internal structure of the scaffold contributes to the complex tensile behaviour of the polymer, the surface of the scaffold remains largely non-porous. The low number of pores minimise access for cells, although primary fibroblasts and epithelial cells do attach and proliferate on the polymer surface. Our data show that with a change in manufacturing protocol to produce porous polymer surfaces, POSS-PCUU may be a potential candidate for overcoming some of the limitations associated with laryngeal reconstruction and regeneration

Bunches of misfit dislocations on the onset of relaxation of Si0.4_{0.4}Ge0.6_{0.6}/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

The experimental x-ray diffraction patterns of a Si$_{0.4}$Ge$_{0.6}$/Si(001) epitaxial film with a low density of misfit dislocations are modeled by the Monte Carlo method. It is shown that an inhomogeneous distribution of 60$^\circ$ dislocations with dislocations arranged in bunches is needed to explain the experiment correctly. As a result of the dislocation bunching, the positions of the x-ray diffraction peaks do not correspond to the average dislocation density but reveal less than a half of the actual relaxation