Quantum Clock Synchronization Based on Shared Prior Entanglement

We demonstrate that two spatially separated parties (Alice and Bob) can utilize shared prior quantum entanglement, and classical communications, to establish a synchronized pair of atomic clocks. In contrast to classical synchronization schemes, the accuracy of our protocol is independent of Alice or Bob's knowledge of their relative locations or of the properties of the intervening medium.Comment: 4 page

Towards photostatistics from photon-number discriminating detectors

We study the properties of a photodetector that has a number-resolving capability. In the absence of dark counts, due to its finite quantum efficiency, photodetection with such a detector can only eliminate the possibility that the incident field corresponds to a number of photons less than the detected photon number. We show that such a {\em non-photon} number-discriminating detector, however, provides a useful tool in the reconstruction of the photon number distribution of the incident field even in the presence of dark counts.Comment: 7 pages, 4 figure

Optical interface created by laser-cooled atoms trapped in the evanescent field surrounding an optical nanofiber

Trapping and optically interfacing laser-cooled neutral atoms is an essential requirement for their use in advanced quantum technologies. Here we simultaneously realize both of these tasks with cesium atoms interacting with a multi-color evanescent field surrounding an optical nanofiber. The atoms are localized in a one-dimensional optical lattice about 200 nm above the nanofiber surface and can be efficiently interrogated with a resonant light field sent through the nanofiber. Our technique opens the route towards the direct integration of laser-cooled atomic ensembles within fiber networks, an important prerequisite for large scale quantum communication schemes. Moreover, it is ideally suited to the realization of hybrid quantum systems that combine atoms with, e.g., solid state quantum devices

Wigner functions for nonclassical states of a collection of two-level atoms

The general theory of atomic angular momentum states is used to derive the Wigner distribution function for atomic angular momentum number states, coherent states, and squeezed states. These Wigner functions W(theta,phi) are represented as a pseudo-probability distribution in spherical coordinates theta and phi on the surface of a sphere of radius the square root of j(j +1) where j is the total angular momentum

Anisotropic Vacuum Induced Interference in Decay Channels

We demonstrate how the anisotropy of the vacuum of the electromagnetic field can lead to quantum interferences among the decay channels of close lying states. Our key result is that interferences are given by the {\em scalar} formed from the antinormally ordered electric field correlation tensor for the anisotropic vacuum and the dipole matirx elements for the two transitions. We present results for emission between two conducting plates as well as for a two photon process involving fluorescence produced under coherent cw excitationComment: 6 pages with 2 figures, to appear in Phys. Rev. Lett. (tentative june 2000

Checklist of Bees (Hymenoptera: Apoidea) From Managed Emergent Wetlands in the Lower Mississippi Alluvial Valley of Arkansas

Background Here we present the results from a two-year bee survey conducted on 18 managed emergent wetlands in the lower Mississippi Alluvial Valley of Arkansas, USA. Sample methods included pan traps, sweep netting and blue-vane traps. We document 83 bee species and morphospecies in 5 families and 31 genera, of which 37 species represent first published state records for Arkansas. The majority of species were opportunistic wetland species; only a small number were wetland-dependent species or species largely restricted to alluvial plains. New information We present new distributional records for bee species not previously recorded in managed emergent wetlands and report specimens of thirty-seven species for which no published Arkansas records exist, expanding the known ranges of Ceratina cockerelli, Diadasia enavata, Lasioglossum creberrimum, Svastracressonii and Dieunomia triangulifera. We also distinguish opportunistic wetland bee species from wetland-dependent and alluvial plain-restricted species

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

Quantum States of Light Produced by a High-Gain Optical Parametric Amplifier for Use in Quantum Lithography

We present a theoretical analysis of the properties of an unseeded optical parametic amplifier (OPA) used as the source of entangled photons for applications in quantum lithography. We first study the dependence of the excitation rate of a two-photon absorber on the intensity of the light leaving the OPA. We find that the rate depends linearly on intensity only for output beams so weak that they contain fewer than one photon per mode. We also study the use of an N-photon absorber for arbitrary N as the recording medium to be used with such a light source. We find that the contrast of the interference pattern and the sharpness of the fringe maxima tend to increase with increasing values of N, but that the density of fringes and thus the limiting resolution does not increase with N. We conclude that the output of an unseeded OPA exciting an N-photon absorber provides an attractive system in which to perform quantum lithography