Optomechanical dual-beam backaction-evading measurement beyond the rotating-wave approximation

We present the exact analytical solution of the explicitly time-periodic quantum Langevin equation describing the dual-beam backaction-evading measurement of a single mechanical oscillator quadrature due to V. B. Braginsky, Y. I. Vorontsov, and K. S. Thorne [Science 209, 547 (1980)] beyond the commonly used rotating-wave approximation. We show that counterrotating terms lead to extra sidebands in the optical and mechanical spectra and to a modification of the main peak. Physically, the backaction of the measurement is due to periodic coupling of the mechanical resonator to a light-field quadrature that only contains cavity-filtered shot noise. Since this fact is independent of other degrees of freedom the resonator might be coupled to, our solution can be generalized, including to dissipatively or parametrically squeezed oscillators, as well as recent two-mode backaction-evading measurements.Royal Society (University Research Fellowship), Winton Programme for the Physics of Sustainabilit

Floquet approach to bichromatically driven cavity-optomechanical systems

We develop a Floquet approach to solve time-periodic quantum Langevin equations in steady state. We show that two-time correlation functions of system operators can be expanded in a Fourier series and that a generalized Wiener-Khinchin theorem relates the Fourier transform of their zeroth Fourier component to the measured spectrum. We apply our framework to bichromatically driven cavity optomechanical systems, a setting in which mechanical oscillators have recently been prepared in quantum-squeezed states. Our method provides an intuitive way to calculate the power spectral densities for time-periodic quantum Langevin equations in arbitrary rotating frames.A.N. holds a University Research Fellowship from the Royal Society and acknowledges additional support from the Winton Programme for the Physics of Sustainability. D.M. acknowledges support by the UK Engineering and Physical Sciences Research Council (EPSRC) under Grant No. EP/M506485/1.This is the author accepted manuscript. The final version is available from the American Physical Society via http://dx.doi.org/10.1103/PhysRevA.94.02380

Current rectification in a double quantum dot through fermionic reservoir engineering

Reservoir engineering is a powerful tool for the robust generation of quantum states or transport properties. Using both a weak-coupling quantum master equation and the exact solution, we show that directional transport of electrons through a double quantum dot can be achieved through an appropriately designed electronic environment. Directionality is attained through the interference of coherent and dissipative coupling. The relative phase is tuned with an external magnetic field, such that directionality can be reversed, as well as turned on and off dynamically. Our work introduces fermionic reservoir engineering, paving the way to a new class of nanoelectronic devices

Stroboscopic quantum optomechanics

We consider an optomechanical cavity that is driven stroboscopically by a train of short pulses. By suitably choosing the inter-pulse spacing we show that ground-state cooling and mechanical squeezing can be achieved, even in the presence of mechanical dissipation and for moderate radiation-pressure interaction. We provide a full quantum-mechanical treatment of stroboscopic backaction-evading measurements, for which we give a simple analytic insight, and discuss preparation and verification of squeezed mechanical states. We further consider stroboscopic driving of a pair of non-interacting mechanical resonators coupled to a common cavity field, and show that they can be simultaneously cooled and entangled. Stroboscopic quantum optomechanics extends measurement-based quantum control of mechanical systems beyond the good-cavity limit.Comment: 9 + 4 pages, 5 figure

Two-Tone Optomechanical Instability and Its Fundamental Implications for Backaction-Evading Measurements

While quantum mechanics imposes a fundamental limit on the precision of interferometric measurements of mechanical motion due to measurement backaction, the nonlinear nature of the coupling also leads to parametric instabilities that place practical limits on the sensitivity by limiting the power in the interferometer. Such instabilities have been extensively studied in the context of gravitational wave detectors, and their presence has recently been reported in Advanced LIGO. Here, we observe experimentally and describe theoretically a new type of optomechanical instability that arises in two-tone backaction-evading (BAE) measurements, designed to overcome the standard quantum limit, and demonstrate the effect in the optical domain with a photonic crystal nanobeam, and in the microwave domain with a micromechanical oscillator coupled to a microwave resonator. In contrast to the well-known oscillatory parametric instability that occurs in single-tone, blue-detuned pumping, which is characterized by a vanishing effective mechanical damping, the parametric instability in balanced two-tone optomechanics is exponential, and is a result of small detuning errors in the two pump frequencies. Its origin can be understood in a rotating frame as the vanishing of the effective mechanical frequency due to an optical spring effect. Counterintuitively, the instability occurs even in the presence of perfectly balanced intracavity fields, and can occur for both signs of detuning. We find excellent quantitative agreement with our theoretical predictions. Since the constraints on tuning accuracy become stricter with increasing probe power, it imposes a fundamental limitation on BAE measurements, as well as other two-tone schemes. In addition to introducing a new limitation in two-tone BAE measurements, the results also introduce a new type of nonlinear dynamics in cavity optomechanics

Detailed quantification of glacier elevation and mass changes in South Georgia

Most glaciers in South America and on the Antarctic Peninsula are retreating and thinning. They are considered strong contributors to global sea level rise. However, there is a lack of glacier mass balance studies in other areas of the Southern Hemisphere, such as the surrounding Antarctic Islands. Here, we present a detailed quantification of the 21st century glacier elevation and mass changes for the entire South Georgia Island using bi-static synthetic aperture radar interferometry between 2000 and 2013. The results suggest a significant mass loss since the beginning of the present century. We calculate an average glacier mass balance of -1.04 0.09 m w.e.a(-1) and a mass loss rate of 2.28 0.19 Gt a(-1) (2000-2013), contributing 0.006 0.001 mm a(-1) to sea-level rise. Additionally, we calculate a subaqueous mass loss of 0.77 0.04 Gt a(-1) (2003-2016), with an area change at the marine and lake-terminating glacier fronts of -6.58 0.33 km(2) a(-1), corresponding to similar to 4% of the total glacier area. Overall, we observe negative mass balance rates in South Georgia, with the highest thinning and retreat rates at the large outlet glaciers located at the north-east coast. Although the spaceborne remote sensing dataset analysed in this research is a key contribution to better understanding of the glacier changes in South Georgia, more detailed field measurements, glacier dynamics studies or further long-term analysis with high-resolution regional climate models are required to precisely identify the forcing factors

Zearalenone production and growth in drinking water inoculated with Fusarium graminearum

Production of the mycotoxin zearalenone (ZEN) was examined in drinking water inoculated with Fusarium graminearum. The strain employed was isolated from a US water distribution system. ZEN was purified with an immunoaffinity column and quantified by high-performance liquid chromatography (HPLC) with fluorescence detection. The extracellular yield of ZEN was 15.0 ng l−1. Visual growth was observed. Ergosterol was also indicative of growth and an average of 6.2 μg l−1 was obtained. Other compounds were also detected although remain unidentified. There is no equivalent information available. More work is required on metabolite expression in water as mycotoxins have consequences for human and animal health. The levels detected in this study were low. Water needs to be accepted as a potential source as it attracts high quality demands in terms of purity.Fundação para a Ciência e a Tecnologia (FCT

Physical and Morphological Properties of [O II] Emitting Galaxies in the HETDEX Pilot Survey

The Hobby-Eberly Dark Energy Experiment pilot survey identified 284 [O II] 3727 emitting galaxies in a 169 square-arcminute field of sky in the redshift range 0 < z < 0.57. This line flux limited sample provides a bridge between studies in the local universe and higher-redshift [O II] surveys. We present an analysis of the star formation rates (SFRs) of these galaxies as a function of stellar mass as determined via spectral energy distribution fitting. The [O II] emitters fall on the "main sequence" of star-forming galaxies with SFR decreasing at lower masses and redshifts. However, the slope of our relation is flatter than that found for most other samples, a result of the metallicity dependence of the [O II] star formation rate indicator. The mass specific SFR is higher for lower mass objects, supporting the idea that massive galaxies formed more quickly and efficiently than their lower mass counterparts. This is confirmed by the fact that the equivalent widths of the [O II] emission lines trend smaller with larger stellar mass. Examination of the morphologies of the [O II] emitters reveals that their star formation is not a result of mergers, and the galaxies' half-light radii do not indicate evolution of physical sizes.Comment: 36 pages, 16 figures, 4 tables, accepted to Ap