On the SU(3) parametrization of qutrits

Parametrization of qutrits on the complex projective plane CP^2 = SU(3)/U(2) is given explicitly. A set of constraints that characterize mixed state density matrices is found.Comment: Paper presented at 12th Central European Workshop on Quantum Optics, 6-9 June 2005, Bilkent Univ., Ankara, Turke

Topological Degeneracy and Vortex Manipulation in Kitaev's Honeycomb Model

The classification of loop symmetries in Kitaev's honeycomb lattice model provides a natural framework to study the Abelian topological degeneracy. We derive a perturbative low-energy effective Hamiltonian that is valid to all orders of the expansion and for all possible toroidal configurations. Using this form we demonstrate at what order the system's topological degeneracy is lifted by finite size effects and note that in the thermodynamic limit it is robust to all orders. Further, we demonstrate that the loop symmetries themselves correspond to the creation, propagation, and annihilation of fermions. We note that these fermions, made from pairs of vortices, can be moved with no additional energy cost

Fairness-Aware Ranking in Search & Recommendation Systems with Application to LinkedIn Talent Search

We present a framework for quantifying and mitigating algorithmic bias in mechanisms designed for ranking individuals, typically used as part of web-scale search and recommendation systems. We first propose complementary measures to quantify bias with respect to protected attributes such as gender and age. We then present algorithms for computing fairness-aware re-ranking of results. For a given search or recommendation task, our algorithms seek to achieve a desired distribution of top ranked results with respect to one or more protected attributes. We show that such a framework can be tailored to achieve fairness criteria such as equality of opportunity and demographic parity depending on the choice of the desired distribution. We evaluate the proposed algorithms via extensive simulations over different parameter choices, and study the effect of fairness-aware ranking on both bias and utility measures. We finally present the online A/B testing results from applying our framework towards representative ranking in LinkedIn Talent Search, and discuss the lessons learned in practice. Our approach resulted in tremendous improvement in the fairness metrics (nearly three fold increase in the number of search queries with representative results) without affecting the business metrics, which paved the way for deployment to 100% of LinkedIn Recruiter users worldwide. Ours is the first large-scale deployed framework for ensuring fairness in the hiring domain, with the potential positive impact for more than 630M LinkedIn members.Comment: This paper has been accepted for publication at ACM KDD 201

Improving fairness in machine learning systems: What do industry practitioners need?

The potential for machine learning (ML) systems to amplify social inequities and unfairness is receiving increasing popular and academic attention. A surge of recent work has focused on the development of algorithmic tools to assess and mitigate such unfairness. If these tools are to have a positive impact on industry practice, however, it is crucial that their design be informed by an understanding of real-world needs. Through 35 semi-structured interviews and an anonymous survey of 267 ML practitioners, we conduct the first systematic investigation of commercial product teams' challenges and needs for support in developing fairer ML systems. We identify areas of alignment and disconnect between the challenges faced by industry practitioners and solutions proposed in the fair ML research literature. Based on these findings, we highlight directions for future ML and HCI research that will better address industry practitioners' needs.Comment: To appear in the 2019 ACM CHI Conference on Human Factors in Computing Systems (CHI 2019

Focus on topological quantum computation

Topological quantum computation started as a niche area of research aimed at employing particles with exotic statistics, called anyons, for performing quantum computation. Soon it evolved to include a wide variety of disciplines. Advances in the understanding of anyon properties inspired new quantum algorithms and helped in the characterization of topological phases of matter and their experimental realization. The conceptual appeal of topological systems as well as their promise for building fault-tolerant quantum technologies fuelled the fascination in this field. This 'focus on' collection brings together several of the latest developments in the field and facilitates the synergy between different approaches

Sozialstaatliche Kürzungspolitik in Deutschland: Nur eine Mär? Eine quantitative Gesetzgebungsanalyse 1974–2014

Quantitative analyses on welfare state dynamics have to cope with the “dependent variable problem”, as studies on social spending reach different conclusions than analyses of replacement rate data. This article suggests a way around this problem by presenting results from a fine-grained analysis of welfare state legislation in Germany between 1974 and 2014. We show that the German welfare state has seen both cuts and expansions occur in all decades. Moreover, we show by means of a regression analysis that partisan politics play a role. Supporting the “Nixon-in-China”-thesis, social democratic governments are associated with a higher probability of cutbacks – especially in times of budgetary pressure – whereas expansions are more likely under Christian democratic governments

Europeanization without substance? EU-Turkey relations and gender equality in employment

This paper focuses on EU-Turkey relations through gender-related employment policy practices. We argue that Turkey is undergoing a process of ‘Europeanization without substance’, in which vague commitments and policy initiatives to enhance female labour force participation coexist uneasily with a contravening political discourse. This is not merely the result of a stalemate in accession negotiations, nor does it stem from the diversity of employment practices across the Union. It rather results from the deliberative discourses used by Turkey’s political leadership to selectively appropriate certain aspects of Europeanization to further a politically motivated agenda that, in essence, negates gender equality altogether. This, we argue in turn, is reflected in a set of practices, policy initiatives, and public statements that make substantive progress in EU-Turkey relations harder. This process is facilitated by the diminishing emphasis placed by the EU on gender equality in employment as manifested by the evolution of gender equality practices at EU level and reinforced by austerity-led policies during the economic crisis