Coupling rotational and translational motion via a continuous measurement in an optomechanical sphere

We consider a measurement of the position of a spot painted on the surface of a trapped nano-optomechanical sphere. The measurement extracts information about the position of the spot and in doing so measures a combination of the orientation and position of the sphere. The quantum backaction of the measurement entangles and correlates these two degrees of freedom. Such a measurement is not available for atoms or ions and provides a mechanism to probe the quantum mechanical properties of trapped optomechanical spheres. In performing simulations of this measurement process we also test a numerical method introduced recently by Rouchon and collaborators [H. Amini, M. Mirrahimi, and P. Rouchon, in Proceedings of the 50th IEEE Conference on Decision and Control (CDC, 2011), pp. 6242–6247; P. Rouchon and J. F. Ralph, Phys. Rev. A 91, 012118 (2015)] for solving stochastic master equations. This method guarantees the positivity of the density matrix when the Lindblad operators for all simultaneous continuous measurements are mutually commuting. We show that it is both simpler and far more efficient than previous methods

Quantum estimation of coupled parameters and the role of entanglement

The quantum Cramer-Rao bound places a limit on the mean square error of a parameter estimation procedure, and its numerical value is determined by the quantum Fisher information. For single parameters, this leads to the well- known Heisenberg limit that surpasses the classical shot-noise limit. When estimating multiple parameters, the situation is more complicated and the quantum Cramer-Rao bound is generally not attainable. In such cases, the use of entanglement typically still offers an enhancement in precision. Here, we demonstrate that entanglement is detrimental when estimating some nuisance parameters. In general, we find that the estimation of coupled parameters does not benefit from either classical or quantum correlations. We illustrate this effect in a practical application for optical gyroscopes

A System for the Generation of Synthetic Wide Area Aerial Surveillance Imagery

The development, benchmarking and validation of aerial Persistent Surveillance (PS) algorithms requires access to specialist Wide Area Aerial Surveillance (WAAS) datasets. Such datasets are difficult to obtain and are often extremely large both in spatial resolution and temporal duration. This paper outlines an approach to the simulation of complex urban environments and demonstrates the viability of using this approach for the generation of simulated sensor data, corresponding to the use of wide area imaging systems for surveillance and reconnaissance applications. This provides a cost-effective method to generate datasets for vehicle tracking algorithms and anomaly detection methods. The system fuses the Simulation of Urban Mobility (SUMO) traffic simulator with a MATLAB controller and an image generator to create scenes containing uninterrupted door-to-door journeys across large areas of the urban environment. This ‘pattern-of-life’ approach provides three-dimensional visual information with natural movement and traffic flows. This can then be used to provide simulated sensor measurements (e.g. visual band and infrared video imagery) and automatic access to ground-truth data for the evaluation of multi-target tracking systems

Quantum Filtering One Bit at a Time

In this Letter we consider the purification of a quantum state using the information obtained from a continuous measurement record, where the classical measurement record is digitized to a single bit per measurement after the measurements have been made. Analysis indicates that efficient and reliable state purification is achievable for one- and two-qubit systems. We also consider quantum feedback control based on the discrete one-bit measurement sequences

Local versus Global Strategies in Multi-parameter Estimation

We consider the problem of estimating multiple phases using a multi-mode interferometer. In this setting we show that while global strategies with multi-mode entanglement can lead to high precision gains, the same precision enhancements can be obtained with mode-separable states and local measurements. The crucial resource for quantum enhancement is shown to be a large number variance in the probe state, which can be obtained without any entanglement between the modes. This has important practical implications because local strategies using separable states have many advantages over global schemes using multi-mode-entangled states. Such advantages include a robustness to local estimation failure, more flexibility in the distribution of resources, and comparatively easier state preparation. We obtain our results by analyzing two different schemes: the first uses a set of interferometers, which can be used as a model for a network of quantum sensors, and the second looks at measuring a number of phases relative to a reference, which is concerned primarily with quantum imaging

Geographical Disparities in Screening and Cancer-Related Health Behaviour.

This study aimed to identify whether cancer-related health behaviours including participation in cancer screening vary by geographic location in Australia. Data were obtained from the 2014-2015 Australian National Health Survey, a computer-assisted telephone interview that measured a range of health-related issues in a sample of randomly selected households. Chi-square tests and adjusted odds ratios from logistic regression models were computed to assess the association between residential location and cancer-related health behaviours including cancer screening participation, alcohol consumption, smoking, exercise, and fruit and vegetable intake, controlling for age, socio-economic status (SES), education, and place of birth. The findings show insufficient exercise, risky alcohol intake, meeting vegetable intake guidelines, and participation in cervical screening are more likely for those living in inner regional areas and in outer regional/remote areas compared with those living in major cities. Daily smoking and participation in prostate cancer screening were significantly higher for those living in outer regional/remote areas. While participation in cancer screening in Australia does not appear to be negatively impacted by regional or remote living, lifestyle behaviours associated with cancer incidence and mortality are poorer in regional and remote areas. Population-based interventions targeting health behaviour change may be an appropriate target for reducing geographical disparities in cancer outcomes

Dynamical model selection for quantum optomechanical systems

This paper considers the problem of distinguishing between different dynamical models using continuous weak measurements; that is, whether the evolution is quantum mechanical or given by a classical stochastic differential equation. We examine the conditions that optimize quantum hypothesis testing, maximizing one's ability to discriminate between classical and quantum models. We set upper limits on the temperature and lower limits on the measurement efficiencies required to explore these differences, using experiments in levitated optomechanical systems as an example