Resource costs for fault-tolerant linear optical quantum computing

Linear optical quantum computing (LOQC) seems attractively simple: information is borne entirely by light and processed by components such as beam splitters, phase shifters and detectors. However this very simplicity leads to limitations, such as the lack of deterministic entangling operations, which are compensated for by using substantial hardware overheads. Here we quantify the resource costs for full scale LOQC by proposing a specific protocol based on the surface code. With the caveat that our protocol can be further optimised, we report that the required number of physical components is at least five orders of magnitude greater than in comparable matter-based systems. Moreover the resource requirements grow higher if the per-component photon loss rate is worse than one in a thousand, or the per-component noise rate is worse than $10^{-5}$. We identify the performance of switches in the network as the single most influential factor influencing resource scaling

Quantum Enhanced Multiple Phase Estimation

We study the simultaneous estimation of multiple phases as a discretised model for the imaging of a phase object. We identify quantum probe states that provide an enhancement compared to the best quantum scheme for the estimation of each individual phase separately, as well as improvements over classical strategies. Our strategy provides an advantage in the variance of the estimation over individual quantum estimation schemes that scales as O(d) where d is the number of phases. Finally, we study the attainability of this limit using realistic probes and photon-number-resolving detectors. This is a problem in which an intrinsic advantage is derived from the estimation of multiple parameters simultaneously.Comment: Accepted by Physical Review Letter

Public Service Decentralisation : Governance Opportunities and Challenges

Background This discussion paper identifies and analyses a number of key governance issues that are relevant to ‘decentralisation’ as a concept in public sector reform. It explores, particularly within the context of contemporary Irish experience, some of the key opportunities and challenges for effective leadership and collegiality in a geographically decentralised Irish civil and public service: areas which may have been comparatively neglected, in both research and policy terms, in the past but which demand further attention for effective implementation of current initiatives. The research draws upon: · an extensive review of the national and international literature on civil/public service decentralisation, as well as effective leadership and positive collegiality in the commercial and non-commercial sectors; · in-depth discussions with those engaged, at a senior level, both in Ireland and elsewhere with developing and implementing decentralisation programmes; · in-depth discussions with the chief officers in a crosssection of Irish public bodies directly affected by the current programme, as well as senior trade union representatives and senior private sector managers; In this regard, it must be stressed that the geographical decentralisation programme currently in hand for the Irish public service will have a direct and/or indirect impact not just on those specific bodies identified for decentralisation under the current programme but will have an impact across the public service as well as in other sectors. Indeed the changes that are afoot are of a scale and character that should lead to a fundamental recasting of the Irish system of public administration. EXECUTIVE SUMMARY Policy context Since 1994, the Irish public service has been engaged upon a long-term programme of public service modernisation, also known as the Strategic Management Initiative (SMI), broadly along New Public Management (NPM) lines. While Ireland’s efforts at geographical decentralisation long predate the SMI and have not, until now, had significant, explicit implications for the modernisation agenda, a considerable sense of urgency has now been injected into this gradually, self-modernising administrative system. For, into a previously consensual and gradualist policy environment, the Minister for Finance in December 2003 announced the Irish government\u27s commitment to the voluntary decentralisation of over 10,300 posts in civil service departments/offices and agencies to over fifty locations across twenty-five counties throughout the country. Of this total, over 3,000 of the posts earmarked for relocation are in state agencies. Additionally, the government decided that, save in exceptional circumstances, any new agencies/bodies being established in the future should be located in areas compatible with this new programme. While decentralisation has not formed an explicit plank of either current or past Irish public service reform initiatives and while Ireland\u27s experience to date has demonstrated little devolution of fiscal and other high-level decision-making functions from central to local levels, the spatial decentralisation of Dublin-based public service employment and functions to non-metropolitan locations has been a feature of Irish administrative reorganisation at least since the 1960s. Broadly speaking, there have been two previous phases of geographical decentralisation in Ireland: (a) dispersal during the period 1967 to 1987; followed by (b) a complex period of dispersal, deconcentration and regionalisation (1988-2003). Thus, even before the new programme is implemented, previous national-level initiatives, together with the adoption of regional strategies by some departments/offices, have already resulted in a complex spatial mosaic of public service locations. Together with dispersed functional units, this complex mosaic includes regionalised and/or county-based offices supported by networks of branch, district and local offices. However, there is little doubt that, although it builds upon these earlier initiatives, the current decentralisation programme will present unprecedented management and operational challenges at the departmental/organisational and publicservice wide levels. It will also be important to learn from experiences in the past regarding leadership and collegiality in a geographically complex civil service in order to help plot the future. The current proposals will not only mean that the majority of civil service, as well as public service, posts will be based outside Dublin but no fewer than eight government departmental HQs will be located away from the capital, while the government itself and many other departments and stakeholder organisations will continue to operate from the centre. As a consequence, an entirely new approach to the governance of the service will be required and, in particular, new models of leadership and collegiality developed. This dramatic policy initiative, in the short-term, has not only reverberated throughout the administrative system, but, in the longer term, has the potential to present hitherto un-thought of opportunities for radical reform and improvements in the way the Irish public service operates. Learning from others A number of other countries have implemented decentralisation initiatives in the past number of decades. For example, in the Netherlands and UK up to the end of the 1980s the decentralisation of public service employment away from the capital had been used as part of a regional development strategy to relieve long-term unemployment in declining industrial areas. More recently, evidence from secondary sources indicates international experience of relocation and decentralisation in a wide range of countries and/or other public administrations; e.g. France, Germany, Norway, Japan and Canada (British Colombia). Internationally, the geographical decentralisation of the civil and public service is seen as an opportunity to secure improved efficiency on the back of business process reengineering (BPR), new working practices and modernisation. However, this research found that, although some useful inferences can be drawn from a review of available international evidence, it is difficult to identify in other public administrations in OECD a direct comparator for the current programme of Irish decentralisation. This lack of a comparator relates to the scale of the current programme, its scope, timing and, above all, its inclusion of proposals to relocate entire organisations in locations away from the capital city and centre of political life. For example, the UK approach specifically excludes the movement of head offices of government departments away from London. Leadership and collegiality Available research evidence suggests that both effective leadership and positive collegiality are key features of good governance and the significance of both these qualities is at a premium within the context of a geographically complex, decentralised civil and public service. Such qualities of good governance as leadership, effectiveness, participation, coherence, programme delivery and effective stakeholder engagement are particularly relevant in the context of the decentralisation programme given the continuing location of the Oireachtas and a number of departments in central Dublin and the particular challenges posed by the geographical decentralisation of others. Indeed, it is important to note that, as early as March 2004, the Decentralisation Implementation Group was beginning to acknowledge the importance of these qualities in forming ‘a post-decentralised civil service’: ‘The geographic relocation and dispersal of staff may help to reinforce existing moves towards greater devolution of authority and responsibility to, and within, organisations. There will be an onus on management at organisational and suborganisational level to exercise greater de facto responsibility for HR, finance and other organisational matters. A more geographically dispersed civil service needs to be balanced by sufficiently strong common values and culture to support effective system-wide co-operation and decision-making. It will be necessary to reinforce, and invest more heavily in corporate culture and ethos’ (First Report of the Decentralisation Implementation Group to Minister for Finance p.28). These opportunities and challenges are explored in this research at corporate/service-wide, interdepartmental and intradepartmental levels A review of the latest international literature and best practice management frameworks clearly highlights that not only is effective leadership the cornerstone upon which organisational excellence is built, it also: · gives strategic direction: it develops and communicates vision, mission and values; · achieves change and focuses efforts on customer service; · develops and implements a system for organisational management and performance review; · motivates and supports people, acting as a role model; · manages the relationships with politicians and other stakeholders, acting in a socially responsible manner. These qualities hold true across the public and private sectors. Effective and visible leadership is required to promote an emphasis on co-operation, consensus, persuasion and the like. A key quality of leadership is also the capacity to operate in a collegial manner and to support collegiality between and within organisations. Together with positive collegiality, these qualities of effective leadership apply at three levels: the corporate or service-wide; the inter- and the intra-departmental. The key research question for this study was to consider the extent to which these qualities of leadership and collegiality could be affected by the geographical dispersal of the public service organisations concerned and, specifically, to identify and discuss opportunities and challenges thus presented. Opportunities and challenges There is little doubt that the current decentralisation programme will have a profound impact on structures, communication frameworks, networking fora and the relationship interface between the civil service, the political and stakeholder systems. How this is managed is vital in terms of the effects on customer service and the efficiency of business processes during the transition phase and beyond. As such, if effectively managed and implemented, it could represent a unique opportunity to fundamentally revisit and restructure the ways in which the civil and wider public services conduct their business. There is little doubt that the movement of public service bodies away from Dublin will provide an unprecedented xiii opportunity for a fundamental overhaul of work done and the way it is done, through the use of business process reengineering and other techniques. Concerns from the past regarding blocked career progression for those in dispersed and regional civil service offices could be ameliorated by adopting a regional approach to facilitate promotion across public service bodies. Otherwise, a move away from Dublin would very definitely become a one-way journey. Because of the travel imperative for contact with the minister and meetings with other public servants, while the burden of travel will be greatly increased, especially when engaged in EU and other international work, it is very likely that both the frequency and management of meetings will become subject to stricter discipline. The use of ICT will help communication but it is expected to be only a limited substitute for face-to-face collegiality. The discussions that took place during this research also suggest that it could be timely to re-explore the potential benefits of a Senior Civil Service. Such an incremental step could support the development of leadership skills training and help sustain collegiality at the service-wide level. Respondents frequently expressed concern that local pressures could lead to a parochial mindset developing. For instance one respondent said: ‘Leadership has not historically been considered as a skill that can be learned - it has been regarded rather as Churchill described ‘greatness’: you can be born with it, achieve it or have it thrust upon you. Yet recent thinking in both the private and public sectors sees the development of the skills of leadership as essential to the effective delivery of any programme of change - and that all efficient organisations are in a state of ordered change’. It was outside the scope of this research to suggest or even less to prescribe firm recommendations for further action. That needs to be on the national agenda for another day. However, although no organisation is scheduled to decentralise before the end of 2006, there is little doubt that, if the current decentralisation programme is to rise above the very considerable logistical issues (around staffing/training and physical infrastructure) that have understandably pre-occupied the implementation agenda to date, then serious consideration of the governance opportunities and challenges arising from this programme need to rise up that agenda. Only two of these issues have been initially reviewed and discussed in this paper: namely effective leadership and positive collegiality. However, it is clear from this research that, if Ireland is to retain its hard won and justified reputation for first rate civil and public services, as well as its international standing, positive action is required across a wide front to turn leadership and collegiality challenges into opportunities. On the basis of this research evidence, such action should include constructive, informed and positive support being given to a wide range of issues, including: · Giving urgent attention to the development of a servicewide Knowledge Management initiative to minimise loss and open up new opportunities for knowledge sharing on a collegial basis, within, between and across those public service bodies significantly affected by the decentralisation programme. Allied to this is the need to map more clearly, and understand better, current formal and informal networks within the service. These will need to be significantly recast. Resort to ICT and large amounts of travel appear to only offer partial solutions. · Implementing a coherent, service-wide change management programme, which recognises and empowers leadership within and across the civil and wider public services. Again models appear to exist, based upon international best practice, which could inform this process, as could the more systematic indepth analysis of private sector experiences. It would appear also that the timing could be opportune for a revisiting and reassertion of core public service values that could help to maintain consistency in the considerably more geographically complex and younger service of the future. Allied and supportive of this approach could be the further examination of the implications for Ireland of the explicit development of a senior civil and public service. In summary, there is little doubt that the current leaders of the Irish public service have had decentralisation thrust upon them, even though it may be up to their successors to fully operationalise the resultant changes from new and diverse localities. While issues of staffing and infrastructure are understandably pre-occupying minds presently concerned with implementation, action will need to be commenced soon to rearticulate, and sustain, the values of the Irish public service and to cultivate the leadership skills necessary for the next generation of secretaries general and chief executives so that the modernisation programme set in motion a decade ago is sustained and re-invigorated. In a decade from now, a new generation of leaders should be leading an entirely recast, modernised civil and public service, in diverse places but with shared values

Career Progression in the Irish Civil Service

Human Resource Management (HRM) reform is central to the current public service modernisation programme or Strategic Management Initiative (SMI). A new approach to HRM is a priority in the Irish civil service due to difficulties in recruiting and retaining the best staff. In particular there is evidence that the civil service is failing to meet the aspirations of its staff in a number of key areas: including earnings, career progression, responsibility, reward and recognition. The need to address staff concerns in these areas is highlighted in the Programme for Prosperity and Fairness (2000) which argues that ‘the civil service has to respond better to the aspirations of staff for more fulfilling work and improved career paths and create workplace conditions and relations which are conducive to increasing job satisfaction,motivation and commitment of staff’ (p. 19). Even with the recent downturn in the economic cycle and the decreased demand for labour in certain areas of the private sector, there is little room for complacency among public service employers. Regardless of the prevailing economic conditions, it is critical that the aspirations of civil servants with respect to career progression and development are met. It is within this context that this paper provides a critical overview of career progression arrangements in the Irish civil service. Throughout the report, career progression is discussed in its broadest sense. Rather than simply describing an individual’s progress up the ranks of an organisation, career progression and development is argued as being relevant to all staff. This approach is consistent with that found in the literature, where career development is described as focusing on the individual and the skills, training and experience they acquire, through their own effort and with the assistance of their employer in the course of their working life. Therefore, while promotion arrangements are of course important, the report also considers other developments essential for effective career progression including induction procedures, performance management, transfer/mobility, training and development. A review of current HRM arrangements indicates that in practice there is a considerable degree of diversity across departments with regard to the range of approaches adopted in relation to career progression. While some of this divergence is due to the size and nature of work of departments, there is also variation in the degree of progress made to date in modernisation. However, consultations with a range of key informants indicate a general consensus that the civil service needs to do more to be perceived as an ‘employer of choice’ by potential quality employees. In addition, it is clear that opportunities for career progression and development play a critical role in this regard. In order to gain an appreciation of how career progression arrangements might be improved, this paper examines the international public sector experience. Most OECD countries are currently pursuing strategies and policies to enhance the professional quality of HRM in the public service. In many countries this is coupled with concerns in relation to recruitment and retention as well as the public service’s competitiveness as an employer compared to the private sector. In response to this situation, public service employers have sought to benchmark salaries against those available in the private sector and increase performance pay, particularly for staff with highly sought after skills. ..

Continuous-Variable Quantum Computing in Optical Time-Frequency Modes using Quantum Memories

We develop a scheme for time-frequency encoded continuous-variable cluster-state quantum computing using quantum memories. In particular, we propose a method to produce, manipulate and measure 2D cluster states in a single spatial mode by exploiting the intrinsic time-frequency selectivity of Raman quantum memories. Time-frequency encoding enables the scheme to be extremely compact, requiring a number of memories that is a linear function of only the number of different frequencies in which the computational state is encoded, independent of its temporal duration. We therefore show that quantum memories can be a powerful component for scalable photonic quantum information processing architectures.Comment: 5 pages, 6 figures, and supplementary information. Updated to be consistent with published versio

An Optimal Design for Universal Multiport Interferometers

Universal multiport interferometers, which can be programmed to implement any linear transformation between multiple channels, are emerging as a powerful tool for both classical and quantum photonics. These interferometers are typically composed of a regular mesh of beam splitters and phase shifters, allowing for straightforward fabrication using integrated photonic architectures and ready scalability. The current, standard design for universal multiport interferometers is based on work by Reck et al (Phys. Rev. Lett. 73, 58, 1994). We demonstrate a new design for universal multiport interferometers based on an alternative arrangement of beam splitters and phase shifters, which outperforms that by Reck et al. Our design occupies half the physical footprint of the Reck design and is significantly more robust to optical losses.Comment: 8 pages, 4 figure

Effective Consultation With The External Customer

Over the past two decades, many countries have embarked upon public service modernisation and development programmes that have sought to alter fundamentally the ways in which citizens are served. These programmes have varied both in their character and pace of change between member states of the Organisation for Economic Co-operation and Development (OECD). However, one common feature has been the efforts made by different public administrations, including here in Ireland, to seek the views of its citizens on a more systematic basis in order to improve the quality of services delivered, to reduce the burden of red-tape and to assist in the development of policy initiatives more geared to the needs of those for whom they are intended. It is within such a setting that this discussion paper focuses specifically on experiences to date and lessons to be learned when public service organisations seek to engage more effectively with their external customers, including not just citizens (who are themselves highly diverse in character) but a wide range of organisations (in the public, private and voluntary sectors), at local, regional, national and international levels. The terms of reference for this study were to: 1. Review and evaluate national/international documentary material, identifying and discussing the key issues to be addressed in order to consult effectively with external customers. 2. Consult with key personnel inside and outside the public service, in order to identify examples of good practice in Ireland and overseas, including innovatory approaches. 3. Explore the implications of different approaches to consultation by public service bodies through in-depth discussions in a selected number of such organisations. 4. Identify and discuss key issues to be addressed by public service bodies to encourage more widespread and effective consultation with external customers. At the outset, the Committee agreed that the study would focus on consultative mechanisms and systems, as well as good practice

Near-term quantum-repeater experiments with nitrogen-vacancy centers: Overcoming the limitations of direct transmission

Quantum channels enable the implementation of communication tasks inaccessible to their classical counterparts. The most famous example is the distribution of secret key. However, in the absence of quantum repeaters, the rate at which these tasks can be performed is dictated by the losses in the quantum channel. In practice, channel losses have limited the reach of quantum protocols to short distances. Quantum repeaters have the potential to significantly increase the rates and reach beyond the limits of direct transmission. However, no experimental implementation has overcome the direct transmission threshold. Here, we propose three quantum repeater schemes and assess their ability to generate secret key when implemented on a setup using nitrogen-vacancy (NV) centers in diamond with near-term experimental parameters. We find that one of these schemes - the so-called single-photon scheme, requiring no quantum storage - has the ability to surpass the capacity - the highest secret-key rate achievable with direct transmission - by a factor of 7 for a distance of approximately 9.2 km with near-term parameters, establishing it as a prime candidate for the first experimental realization of a quantum repeater.Comment: 19+17 pages, 17 figures. v2: added "Discussion and future outlook" section and expanded introduction, published versio