A note on the generalized min-sum set cover problem

In this paper, we consider the generalized min-sum set cover problem, introduced by Azar, Gamzu, and Yin. Bansal, Gupta, and Krishnaswamy give a 485-approximation algorithm for the problem. We are able to alter their algorithm and analysis to obtain a 28-approximation algorithm, improving the performance guarantee by an order of magnitude. We use concepts from $\alpha$-point scheduling to obtain our improvements

Methodology for bus layout for topological quantum error correcting codes

Most quantum computing architectures can be realized as two-dimensional lattices of qubits that interact with each other. We take transmon qubits and transmission line resonators as promising candidates for qubits and couplers; we use them as basic building elements of a quantum code. We then propose a simple framework to determine the optimal experimental layout to realize quantum codes. We show that this engineering optimization problem can be reduced to the solution of standard binary linear programs. While solving such programs is a NP-hard problem, we propose a way to find scalable optimal architectures that require solving the linear program for a restricted number of qubits and couplers. We apply our methods to two celebrated quantum codes, namely the surface code and the Fibonacci code.Comment: 11 pages, 12 figure

Identifying capacitive and inductive loss in lumped element superconducting hybrid titanium nitride/aluminum resonators

We present a method to systematically locate and extract capacitive and inductive losses in superconducting resonators at microwave frequencies by use of mixed-material, lumped element devices. In these devices, ultra-low loss titanium nitride was progressively replaced with aluminum in the inter-digitated capacitor and meandered inductor elements. By measuring the power dependent loss at 50 mK as the Al-TiN fraction in each element is increased, we find that at low electric field, i.e. in the single photon limit, the loss is two level system in nature and is correlated with the amount of Al capacitance rather than the Al inductance. In the high electric field limit, the remaining loss is linearly related to the product of the Al area times its inductance and is likely due to quasiparticles generated by stray radiation. At elevated temperature, additional loss is correlated with the amount of Al in the inductance, with a power independent TiN-Al interface loss term that exponentially decreases as the temperature is reduced. The TiN-Al interface loss is vanishingly small at the 50 mK base temperature.Comment: 10 pages, 5 figure

Etch Induced Microwave Losses in Titanium Nitride Superconducting Resonators

We have investigated the correlation between the microwave loss and patterning method for coplanar waveguide titanium nitride resonators fabricated on Si wafers. Three different methods were investigated: fluorine- and chlorine-based reactive ion etches and an argon-ion mill. At high microwave probe powers the reactive etched resonators showed low internal loss, whereas the ion-milled samples showed dramatically higher loss. At single-photon powers we found that the fluorine-etched resonators exhibited substantially lower loss than the chlorine-etched ones. We interpret the results by use of numerically calculated filling factors and find that the silicon surface exhibits a higher loss when chlorine-etched than when fluorine-etched. We also find from microscopy that re-deposition of silicon onto the photoresist and side walls is the probable cause for the high loss observed for the ion-milled resonator

What works and for whom: a review of OECD countries' experiences with active labour market policies

Although rather discouraging in general, the evaluation literature indicates some measures that have been successful. Job-search assistance, wage subsidies in the private sector, and labour market training do work for some groups, even if the impacts are not large. Also, the evaluation literature focuses on the impacts of one-off programs. Regular interventions, such as job-search monitoring, intensive interviews, and referrals to vacant jobs, have rarely been evaluated rigorously. Recently, introduced "activation" strategies in some OECD countries do appear to yield significant employment gains for participants. An important element in such strategies is experiments with alternative ways of improving the performance of the public employment service. Activation policies which combine high-quality assistance to find work with pressure on unemployed people to accept job offers can be effective with respect to unemployment duration, but more rapid returns to work sometimes comes at the cost of accepting lower re-employment earnings. Although active policies might give rise to displacement effects in the short run, this need not be case the over the medium run of a few years. Declines in structural employment rates achieved by many OECD countries in the 1990s give some reasons for optimism in this respect.job search; wage subsidies; labour market training

Cooperation after War: International Development in Bosnia, 1995 to 1999

This paper discusses how predispositions, incentives, the number and heterogeneity of participants, and leadership (Faerman et al. 2001) jointly influenced the international effort to develop Bosnia and Herzegovina. International coalitions, task forces, and advisory groups are increasingly charged with implementing reforms following civil conflict. This requires a complex web of interorganizational relationships among NGOS, donors and host nations at both global and ‘ground’ levels. To better understand development assistance, attention must be paid to the relationships between these varied players. We find that four factors influenced relationships between policy, donor, and implementing organizations; and those strained relationships, in turn, affected development success. The paper draws on interviews, conducted in Bosnia, with 43 development professionals, observation of development meetings in Tuzla and Sarajevo, and review of related documents from international development programs.international development, interorganizational relationships and cooperation