Dissipation in a rotating frame: master equation, effective temperature and Lamb-shift

Motivated by recent realizations of microwave-driven nonlinear resonators in superconducting circuits, the impact of environmental degrees of freedom is analyzed as seen from a rotating frame. A system plus reservoir model is applied to consistently derive in the weak coupling limit the master equation for the reduced density in the moving frame and near the first bifurcation threshold. It turns out that additional interactions between momenta of system and bath appear which have been omitted in previous studies. Explicit expressions for the effective temperature and the Lamb-shift are given which for ohmic baths are in agreement with experimental findings, while for structured environments population inversion is predicted that may qualitatively explain recent observations.Comment: 7 pages, 5 figure

Electron-phonon coupling and longitudinal mechanical-mode cooling in a metallic nanowire

We investigate electron-phonon coupling in a narrow suspended metallic wire, in which the phonon modes are restricted to one dimension but the electrons behave three-dimensionally. Explicit theoretical results related to the known bulk properties are derived. We find out that longitudinal vibration modes can be cooled by electronic tunnel refrigeration far below the bath temperature provided the mechanical quality factors of the modes are sufficiently high. The obtained results apply to feasible experimental configurations.Comment: 4+ pages, 3 figure

Generation of Squeezed States of Nanomechanical Resonators by Reservoir Engineering

An experimental demonstration of a non-classical state of a nanomechanical resonator is still an outstanding task. In this paper we show how the resonator can be cooled and driven into a squeezed state by a bichromatic microwave coupling to a charge qubit. The stationary oscillator state exhibits a reduced noise in one of the quadrature components by a factor of 0.5 - 0.2. These values are obtained for a 100 MHz resonator with a Q-value of 10$^4$ to 10$^5$ and for support temperatures of T $\approx$ 25 mK. We show that the coupling to the charge qubit can also be used to detect the squeezed state via measurements of the excited state population. Furthermore, by extending this measurement procedure a complete quantum state tomography of the resonator state can be performed. This provides a universal tool to detect a large variety of different states and to prove the quantum nature of a nanomechanical oscillator.Comment: 13 pages,9 figure

Noise-enabled precision measurements of a Duffing nanomechanical resonator

We report quantitative experimental measurements of the nonlinear response of a radiofrequency mechanical resonator, with very high quality factor, driven by a large swept-frequency force. We directly measure the noise-free transition dynamics between the two basins of attraction that appear in the nonlinear regime, and find good agreement with those predicted by the one-dimensional Duffing equation of motion. We then measure the response of the transition rates to controlled levels of white noise, and extract the activation energy from each basin. The measurements of the noise-induced transitions allow us to obtain precise values for the critical frequencies, the natural resonance frequency, and the cubic nonlinear parameter in the Duffing oscillator, with direct applications to high sensitivity parametric sensors based on these resonators.Comment: 5 pages, 5 figure

Outbreak of tropical rat mite (Ornithonyssus bacoti) dermatitis in a home for disabled persons

Five mentally handicapped individuals living in a home for disabled persons in Southern Germany were seen in our outpatient department with pruritic, red papules predominantly located in groups on the upper extremities, neck, upper trunk and face. Over several weeks 40 inhabitants and 5 caretakers were affected by the same rash. Inspection of their home and the sheds nearby disclosed infestation with rat populations and mites. Finally the diagnosis of tropical rat mite dermatitis was made by the identification of the arthropod Ornithonyssus bacoti or so-called tropical rat mite. The patients were treated with topical corticosteroids and antihistamines. After elimination of the rats and disinfection of the rooms by a professional exterminator no new cases of rat mite dermatitis occurred. The tropical rat mite is an external parasite occurring on rats, mice, gerbils, hamsters and various other small mammals. When the principal animal host is not available, human beings can become the victim of mite infestation. Copyright (c) 2007 S. Karger AG, Base

Force-detected nuclear magnetic resonance: Recent advances and future challenges

We review recent efforts to detect small numbers of nuclear spins using magnetic resonance force microscopy. Magnetic resonance force microscopy (MRFM) is a scanning probe technique that relies on the mechanical measurement of the weak magnetic force between a microscopic magnet and the magnetic moments in a sample. Spurred by the recent progress in fabricating ultrasensitive force detectors, MRFM has rapidly improved its capability over the last decade. Today it boasts a spin sensitivity that surpasses conventional, inductive nuclear magnetic resonance detectors by about eight orders of magnitude. In this review we touch on the origins of this technique and focus on its recent application to nanoscale nuclear spin ensembles, in particular on the imaging of nanoscale objects with a three-dimensional (3D) spatial resolution better than 10 nm. We consider the experimental advances driving this work and highlight the underlying physical principles and limitations of the method. Finally, we discuss the challenges that must be met in order to advance the technique towards single nuclear spin sensitivity -- and perhaps -- to 3D microscopy of molecules with atomic resolution.Comment: 15 pages & 11 figure

A Spin-Mechanical Device for Detection and Control of Spin Current by Nanomechanical Torque

We propose a spin-mechanical device to control and detect spin currents by mechanical torque. Our hybrid nano-electro-mechanical device, which contains a nanowire with a ferromagnetic-nonmagnetic interface, is designed to measure or induce spin polarized currents. Since spin carries angular momentum, a spin flip or spin transfer process involves a change in angular momentum--and hence, a torque--which enables mechanical measurement of spin flips. Conversely, an applied torque can result in spin polarization and spin current.Comment: 6 pages, 2 figure

Potential role for clinical calibration to increase engagement with and application of home telemonitoring: a report from the HeartCycle programme

Aims: There is a need for alternative strategies that might avoid recurrent admissions in patients with heart failure. Home Telemonitoring (HTM) to monitor patient’s symptoms from a distance may be useful. This study attempts to assess changes in HTM vital signs in response to daily life activities (variations in medication, salt intake, exercise and stress) and to stablish which variations affect weight, blood pressure (BP) and heart rate (HR). Methods and results: We assessed 76 patients with heart failure (mean age 76 ± 10.8 years, 75% male, mainly in NYHA class II/III and from ischaemic etiology cause). Patients were given a calendar of interventions scheduling activities approximately twice-a-week before measuring their vital signs. Eating salty food or a large meal were the activities that had a significant impact on weight gain (+0.3 kg; p<0.001 and p=0.006, respectively). Exercise and skipping a dose of medication other than diuretics increased heart rate (+3 bpm, p=0.001 and almost +2 bpm, p=0.016, respectively). Conclusions: Our HTM system was able to detect small changes in vital signs related to these activities. Further studies should assess if providing such a schedule of activities might be useful for patient education and could improve long-term adherence to recommended lifestyle changes

Identifying and exploring factors influencing career choice, recruitment and retention of anaesthesia trainees in the UK

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Entanglement and decoherence of a micromechanical resonator via coupling to a Cooper box

We analyse the quantum dynamics of a micromechanical resonator capacitively coupled to a Cooper box. With appropriate quantum state control of the Cooper box, the resonator can be driven into a superposition of spatially separated states. The Cooper box can also be used to probe the environmentally-induced decoherence of the resonator superposition state.Comment: 4 pages, 3 figure