Quantum noise of non-ideal Sagnac speed meter interferometer with asymmetries

The speed meter concept has been identified as a technique that can potentially provide laser-interferometric measurements at a sensitivity level which surpasses the Standard Quantum Limit (SQL) over a broad frequency range. As with other sub-SQL measurement techniques, losses play a central role in speed meter interferometers and they ultimately determine the quantum noise limited sensitivity that can be achieved. So far in the literature, the quantum noise limited sensitivity has only been derived for lossless or lossy cases using certain approximations (for instance that the arm cavity round trip loss is small compared to the arm cavity mirror transmission). In this article we present a generalised, analytical treatment of losses in speed meters that allows accurate calculation of the quantum noise limited sensitivity of Sagnac speed meters with arm cavities. In addition, our analysis allows us to take into account potential imperfections in the interferometer such as an asymmetric beam splitter or differences of the reflectivities of the two arm cavity input mirrors. Finally,we use the examples of the proof-of-concept Sagnac speed meter currently under construction in Glasgow and a potential implementation of a Sagnac speed meter in the Einstein Telescope (ET) to illustrate how our findings affect Sagnac speed meters with meter- and kilometre-long baselines.Comment: 22 pages, 8 figures, 1 table, (minor corrections and changes made to text and figures in version 2

Experimental demonstration of coupled optical springs

Optical rigidity will play an important role in improving the sensitivity of future generations of gravitational wave (GW) interferometers, which employ high laser power in order to reach and exceed the standard quantum limit. Several experiments have demonstrated the combined effect of two optical springs on a single system for very low-weight mirror masses or membranes. In this paper we investigate the complex interactions between multiple optical springs and the surrounding apparatus in a system of comparable dynamics to a large-scale GW detector. Using three 100 g mirrors to form a coupled cavity system capable of sustaining two or more optical springs, we demonstrate a number of different regimes of opto-mechanical rigidity and measurement techniques. Our measurements reveal couplings between each optical spring and the control loops that can affect both the achievable increase in sensitivity and the stability of the system. Hence this work establishes a better understanding of the realisation of these techniques and paves the way to their application in future GW observatories, such as upgrades to Advanced LIGO

Candidates for a possible third-generation gravitational wave detector: comparison of ring-Sagnac and sloshing-Sagnac speedmeter interferometers

Speedmeters are known to be quantum non-demolition devices and, by potentially providing sensitivity beyond the standard quantum limit, become interesting for third generation gravitational wave detectors. Here we introduce a new configuration, the sloshing-Sagnac interferometer, and compare it to the more established ring-Sagnac interferometer. The sloshing-Sagnac interferometer is designed to provide improved quantum noise limited sensitivity and lower coating thermal noise than standard position meter interferometers employed in current gravitational wave detectors. We compare the quantum noise limited sensitivity of the ring-Sagnac and the sloshing-Sagnac interferometers, in the frequency range, from 5 Hz to 100 Hz, where they provide the greatest potential benefit. We evaluate the improvement in terms of the unweighted noise reduction below the standard quantum limit, and by finding the range up to which binary black hole inspirals may be observed. The sloshing-Sagnac was found to give approximately similar or better sensitivity than the ring-Sagnac in all cases. We also show that by eliminating the requirement for maximally-reflecting cavity end mirrors with correspondingly-thick multi-layer coatings, coating noise can be reduced by a factor of approximately 2.2 compared to conventional interferometers

The failure of suicide prevention in primary care: family and GP perspectives - a qualitative study

Background Although Primary care is crucial for suicide prevention, clinicians tend to report completed suicides in their care as non-preventable. We aimed to examine systemic inadequacies in suicide prevention from the perspectives of bereaved family members and GPs.Methods Qualitative study of 72 relatives or close friends bereaved by suicide and 19 General Practitioners who have experienced the suicide of patients.Results Relatives highlight failures in detecting symptoms and behavioral changes and the inability of GPs to understand the needs of patients and their social contexts. A perceived overreliance on anti-depressant treatment is a major source of criticism by family members. GPs tend to lack confidence in the recognition and management of suicidal patients, and report structural inadequacies in service provision.Conclusions Mental health and primary care services must find innovative and ethical ways to involve families in the decision-making process for patients at risk of suicide

Smart Charging Technologies for Portable Electronic Devices

In this article we describe our efforts of extending demand-side control concepts to the application in portable electronic devices, such as laptop computers, mobile phones and tablet computers. As these devices feature built-in energy storage (in the form of batteries) and the ability to run complex control routines, they are well-suited for the implementation of smart charging concepts. We developed simple hardware and software based prototypes of smart charging controllers for a laptop computer that steer the charging process depending on the frequency of the electricity grid and in case of the software implementation also based on the battery charge status. If similar techniques are incorporated into millions of devices in UK households, this can contribute significantly to the stability of the electricity grid, help to mitigate the short-term power production fluctuations from renewable energy sources and avoid the high cost of building and maintaining conventional power plants as standby reserve

Local-Oscillator Noise Coupling in Balanced Homodyne Readout for Advanced Gravitational Wave Detectors

The second generation of interferometric gravitational wave detectors are quickly approaching their design sensitivity. For the first time these detectors will become limited by quantum back-action noise. Several back-action evasion techniques have been proposed to further increase the detector sensitivity. Since most proposals rely on a flexible readout of the full amplitude- and phase-quadrature space of the output light field, balanced homodyne detection is generally expected to replace the currently used DC readout. Up to now, little investigation has been undertaken into how balanced homodyne detection can be successfully transferred from its ubiquitous application in table-top quantum optics experiments to large-scale interferometers with suspended optics. Here we derive implementation requirements with respect to local oscillator noise couplings and highlight potential issues with the example of the Glasgow Sagnac Speed Meter experiment, as well as for a future upgrade to the Advanced LIGO detectors.Comment: 7 pages, 5 figure

Design of a speed meter interferometer proof-of-principle experiment

The second generation of large scale interferometric gravitational wave detectors will be limited by quantum noise over a wide frequency range in their detection band. Further sensitivity improvements for future upgrades or new detectors beyond the second generation motivate the development of measurement schemes to mitigate the impact of quantum noise in these instruments. Two strands of development are being pursued to reach this goal, focusing both on modifications of the well-established Michelson detector configuration and development of different detector topologies. In this paper, we present the design of the world's first Sagnac speed meter interferometer which is currently being constructed at the University of Glasgow. With this proof-of-principle experiment we aim to demonstrate the theoretically predicted lower quantum noise in a Sagnac interferometer compared to an equivalent Michelson interferometer, to qualify Sagnac speed meters for further research towards an implementation in a future generation large scale gravitational wave detector, such as the planned Einstein Telescope observatory.Comment: Revised version: 16 pages, 6 figure

Supported accommodation for people with mental health problems: the QuEST research programme with feasibility RCT

This work was produced by Killaspy et al. under the terms of a commissioning contract issued by the Secretary of State for Health and Social Care. This issue may be freely reproduced for the purposes of private research and study and extracts (or indeed, the full report) may be included in professional journals provided that suitable acknowledgement is made and the reproduction is not associated with any form of advertising. Applications for commercial reproduction should be addressed to: NIHR Journals Library, National Institute for Health Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK. Background Across England, around 60,000 people live in mental health supported accommodation: residential care, supported housing and floating outreach. Residential care and supported housing provide on-site support (residential care provides the highest level), whereas floating outreach staff visit people living in their own tenancies. Despite their abundance, little is known about the quality and outcomes of these services. Objectives The aim was to assess the quality, costs and effectiveness of mental health supported accommodation services in England. The objectives were (1) to adapt the Quality Indicator for Rehabilitative Care (QuIRC) and the Client Assessment of Treatment scale for use in mental health supported accommodation services; (2) to assess the quality and costs of these services in England and the proportion of people who ‘move on’ to less supported accommodation without placement breakdown (e.g. to move from residential care to supported housing or supported housing to floating outreach, or, for those receiving floating outreach, to manage with fewer hours of support); (3) to identify service and service user factors (including costs) associated with greater quality of life, autonomy and successful move-on; and (4) to carry out a feasibility trial to assess the required sample size and appropriate outcomes for a randomised evaluation of two existing models of supported accommodation. Design Objective 1 – focus groups with staff (n = 12) and service users (n = 16); psychometric testing in 52 services, repeated in 87 services (adapted QuIRC) and with 618 service users (adapted Client Assessment of Treatment scale). Objectives 2 and 3 – national survey and prospective cohort study involving 87 services (residential care, n = 22; supported housing, n = 35; floating outreach, n = 30) and 619 service users followed over 30 months; qualitative interviews with 30 staff and 30 service users. Objective 4 – individually randomised, parallel-group feasibility trial in three centres. Setting English mental health supported accommodation services. Participants Staff and users of mental health supported accomodation services. Interventions Feasibility trial involved two existing models of supported accommodation: supported housing and floating outreach. Main outcome measures Cohort study – proportion of participants who successfully moved to less supported accommodation at 30 months’ follow-up without placement breakdown. Feasibility trial – participant recruitment and withdrawal rates. Results The adapted QuIRC [QuIRC: Supported Accomodation (QuIRC-SA)] had excellent inter-rater reliability, and exploratory factor analysis confirmed its structural validity (all items loaded onto the relevant domain at the > ± 0.3 level). The adapted Client Assessment of Treatment for Supported Accommodation had good internal consistency (Cronbach’s alpha 0.89) and convergent validity (r s = 0.369; p < 0.001). Supported housing services scored higher than residential care and floating outreach on six out of seven QuIRC-SA quality domains. Service users had a high prevalence of severe self-neglect (57%) and vulnerability to exploitation (37%). Those in supported housing (25%) and floating outreach (20%) experienced more crime than those in residential care (4%) but had greater autonomy. Residential care was the most expensive service (mean cost per resident per week was £581 for residential care, £261 for supported housing and £66 for floating outreach) but supported users with the greatest needs. After adjusting for clinical differences, quality of life was similar for users of supported housing and residential care (mean difference –0.138, 95% confidence interval –0.402 to 0.126; p = 0.306), whereas autonomy was greater for supported housing users (mean difference 0.145, 95% confidence interval 0.010 to 0.279; p = 0.035). Qualitative interviews showed that staff and service users shared an understanding of service goals and what constituted effective support. After adjusting for clinical differences, those in floating outreach were more likely to move on successfully at 30 months’ follow-up than those in residential care [odds ratio (OR) 7.96; p < 0.001] and supported housing (OR 2.74; p < 0.001), and this was more likely for users of supported housing than residential care (OR 2.90; p = 0.04). Successful move-on was positively associated with scores on two QuIRC-SA domains: the degree to which the service promoted ‘human rights’ (e.g. facilitating access to advocacy) and ‘recovery-based practice’ (e.g. holding therapeutic optimism and providing collaborative, individualised care planning). Service use costs for those who moved on were significantly lower than for those who did not. Recruitment in the feasibility trial was difficult: 1432 people were screened but only eight were randomised. Barriers included concerns about accommodation being decided at random and a perceived lack of equipoise among clinicians who felt that individuals needed to ‘step down’ from supported housing to floating outreach services. Conclusions We did not find clear evidence on the most effective model(s) of mental health supported accommodation. Indeed, our feasibility study suggests that trials comparing effectiveness cannot be conducted in this country. A range of options are required to provide appropriate support to individuals with differing needs. Future work Future research in this field requires alternatives to trials. Service planners should be guided by the mental health needs of the local population and the pros and cons of the different services that our study identified, rather than purely financial drivers. Trial registration Current Controlled Trials ISRCTN19689576. Funding This programme was funded by the National Institute for Heath Research (NIHR) Programme Grants for Applied Research programme and will be published in full in Programme Grants for Applied Research; Vol. 7, No. 7. See the NIHR Journals Library website for further project information. The fundholders are Camden and Islington NHS Foundation Trust and the research is a collaboration between University College London, Queen Mary University of London, King’s College London, the University of Ulster and Durham University. The research reported in this issue of the journal was funded by PGfAR as project number RP-PG-0610-10097

Effects of static and dynamic higher-order optical modes in balanced homodyne readout for future gravitational waves detectors

With the recent detection of Gravitational waves (GW), marking the start of the new field of GW astronomy, the push for building more sensitive laser-interferometric gravitational wave detectors (GWD) has never been stronger. Balanced homodyne detection (BHD) allows for a quantum noise (QN) limited readout of arbitrary light field quadratures, and has therefore been suggested as a vital building block for upgrades to Advanced LIGO and third generation observatories. In terms of the practical implementation of BHD, we develop a full framework for analyzing the static optical high order modes (HOMs) occurring in the BHD paths related to the misalignment or mode matching at the input and output ports of the laser interferometer. We find the effects of HOMs on the quantum noise limited sensitivity is independent of the actual interferometer configuration, e.g. Michelson and Sagnac interferometers are effected in the same way. We show that misalignment of the output ports of the interferometer (output misalignment) only effects the high frequency part of the quantum noise limited sensitivity (detection noise). However, at low frequencies, HOMs reduce the interferometer response and the radiation pressure noise (back action noise) by the same amount and hence the quantum noise limited sensitivity is not negatively effected in that frequency range. We show that the misalignment of laser into the interferometer (input misalignment) produces the same effect as output misalignment and additionally decreases the power inside the interferometer. We also analyze dynamic HOM effects, such as beam jitter created by the suspended mirrors of the BHD. Our analyses can be directly applied to any BHD implementation in a future GWD. Moreover, we apply our analytical techniques to the example of the speed meter proof of concept experiment under construction in Glasgow. We find that for our experimental parameters, the performance of our seismic isolation system in the BHD paths is compatible with the design sensitivity of the experiment