Near-optimal two-mode spin squeezing via feedback

We propose a feedback scheme for the production of two-mode spin squeezing. We determine a general expression for the optimal feedback, which is also applicable to the case of single-mode spin squeezing. The two-mode spin squeezed states obtained via this feedback are optimal for j=1/2 and are very close to optimal for j>1/2. In addition, the master equation suggests a Hamiltonian that would produce two-mode spin squeezing without feedback, and is analogous to the two-axis countertwisting Hamiltonian in the single mode case.Comment: 10 pages, 6 figures, journal versio

Efficiency and productivity growth comparisons of European and U.S. Air carriers: A first look at the data

In this paper we carry out technical efficiency and productivity growth comparisons among the four largest European carriers and eight of their American counterparts. The time period of our comparisons is 1976 through 1986. This is a particularly interesting period since it begins just after the informal steps toward deregulation in the United States and ends just prior to the introduction of the first wave of reforms by the Council of Ministers in Europe. We also identify the potential efficiency gains of the European liberalization by comparing efficiency differences between the two carrier groups. The reductions in inefficiency describe the amount that inputs can be decreased without altering output.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47558/1/11123_2005_Article_BF01073469.pd

Explaining Differences in Milk Quota Values: The Role of Economic Efficiency

This article explores the relationship between milk quota values and economic efficiency in order to analyze government interventions in quota allocations among producers. For this purpose, we estimate quota values using a panel of Spanish dairy farms. Quota values are then decomposed into economic efficiency, price, and scale effects in order to assess the relative influence of these factors. We find that efficiency is important in explaining quota values but is uncorrelated with observable farm characteristics. This casts doubts on the government's ability to allocate quotas to efficient farms. Copyright 2006, Oxford University Press.

Economies of Scope and Density in the Market for Real Estate Brokerage Services

Using a multiproduct translog cost function, this paper examines the case for economies of scope and density in the market for residential real estate brokerage services. Earlier research that treated output as a homogeneous commodity reported modest economies of scale for this industry. The results of this study suggest that the composition of output is an important source of these scale economies, rather than simply the size of the firm. The economies of scope which we find imply that a balanced mix of listing and sales is the least costly type of operation, a result borne out by the product mix found in our sample. The results also show product-specific diseconomies of scale, suggesting that specialization in either listing or sales may be sub-optimal under the current institutional arrangements present in the market. Finally, market density appears to be, at best, only a nominal source of savings for real estate brokerage firms. Copyright American Real Estate and Urban Economics Association.