Optical Quantum Computation

We review the field of Optical Quantum Computation, considering the various implementations that have been proposed and the experimental progress that has been made toward realizing them. We examine both linear and nonlinear approaches and both particle and field encodings. In particular we discuss the prospects for large scale optical quantum computing in terms of the most promising physical architectures and the technical requirements for realizing them

Phase-dependent decoherence of optical transitions in Pr3+:LaF3 in the presence of a driving field

The decoherence times of orthogonally phased components of the optical transition dipole moment in a two-level system have been observed to differ by an order of magnitude. This phase anisotropy is observed in coherent transient experiments where an optical driving field is present during extended periods of decoherence. The decoherence time of the component of the dipole moment in phase with the driving field is extended compared to T_2, obtained from two-pulse photon echoes, in analogy with the spin locking technique of NMR.Comment: 5 pages, 2 figures; replaced with published versio

Experimental semi-device-independent certification of entangled measurements

Certifying the entanglement of quantum states with Bell inequalities allows one to guarantee the security of quantum information protocols independently of imperfections in the measuring devices. Here we present a similar procedure for witnessing entangled measurements, which play a central role in many quantum information tasks. Our procedure is termed semi-device-independent, as it uses uncharacterized quantum preparations of fixed Hilbert space dimension. Using a photonic setup, we experimentally certify an entangled measurement using measurement statistics only. We also apply our techniques to certify unentangled but nevertheless inherently quantum measurements.Comment: 7 pages, 2 figure

Creation of Maximally Entangled Photon Number States using Optical Fibre Multiports

We theoretically demonstrate a method for producing the maximally path-entangled state (1/Sqrt[2]) (|N,0> + exp[iN phi] |0,N>) using intensity-symmetric multiport beamsplitters, single photon inputs, and either photon-counting postselection or conditional measurement. The use of postselection enables successful implementation with non-unit efficiency detectors. We also demonstrate how to make the same state more conveniently by replacing one of the single photon inputs by a coherent state

Survey of New Zealand farmer intentions and opinions, October-December 1986

This survey is the ninth major survey of New Zealand Farmer Intentions and Opinions. All have been aimed at providing policy makers and those in the agri-business sector in New Zealand with data on which they can formulate policies and planning. The surveys have been continued in response to demands from those who want data on what farmers are intending to do, what they are thinking on major issues, aspects of the financial side, and what are some of the factors that determine their input purchases. In this survey were inserted special questions on financial matters raised in earlier surveys. In addition some questions were included to ascertain some feelings and views of the rural sector on a range of issues including insurance, the News Media and Transport

Violation of the Leggett-Garg inequality with weak measurements of photons

By weakly measuring the polarization of a photon between two strong polarization measurements, we experimentally investigate the correlation between the appearance of anomalous values in quantum weak measurements, and the violation of realism and non-intrusiveness of measurements. A quantitative formulation of the latter concept is expressed in terms of a Leggett-Garg inequality for the outcomes of subsequent measurements of an individual quantum system. We experimentally violate the Leggett-Garg inequality for several measurement strengths. Furthermore, we experimentally demonstrate that there is a one-to-one correlation between achieving strange weak values and violating the Leggett-Garg inequality.Comment: 5 pages, 4 figure

The state of agricultural credit in New Zealand

In this paper the subject of agricultural credit has been subdivided into three sections covering background, borrowing, and lending. The background covers some of the changes in the New Zealand economy and government policies which have affected both borrowers and lenders in the agricultural sector, and consequently the amount and form of credit used. The section on borrowing (Section 3) examines the present credit needs of farmers, in particular the apparent trends towards increased equity and greater difficulty in servicing debt. The lending section (Section 4) examines the roles of government and private lending institutions in the field of agricultural credit and changes in the amount and form of credit available

A review of agricultural credit in New Zealand

The following discussion of the agricultural credit market encompasses agriculture in its wider sense. Because most of the available information and data on agricultural credit is concerned with traditional forms of pastoral farming (sheep, beef and dairy) the discussion relates primarily to those sectors. However, the growing importance of other sectors such as horticulture, grain cropping and deer farming is recognised and where possible their credit situation is also considered. The purpose of the paper is to update previous research by the Agricultural Economics Research Unit into the financing of the agriculture industry. In the past the agricultural credit situation has been relatively stable. Because of its large contribution to exports, agriculture (pastoral agriculture in particular) received considerable support from Government in the form of policies aimed at maintaining a steady flow of investment. Credit assistance was one of the cornerstones of these policies. In 1982 the Government began to change its stance. In the Budget of that year interest payments and certain development ceased to be tax deductible where the farm property was sold within 10 years of purchase. Although this steadied inflation in land prices, long term investors particularly pastoral farm investors still enjoyed considerable advantages over investors wishing to borrow capital for diversification into or expansion of enterprises which were capable of better returns on investment. It was not until late 1984 that a wide range of policies were introduced to remove these advantages and promote greater equity between enterprises and industries requiring capital for restructuring or expansion. As a result some of the conclusions reached in Discussion Papers on agricultural and horticultural credit published by the Unit as recently as April and October 1984 have been quickly overtaken by economic events and need updating. This paper begins with a background of trends in the New Zealand economy and then in chronological order details recent changes in Government Policy. This is followed by a discussion of the implications of these changes for the financing of agriculture. Finally the present state of the agricultural credit market is discussed and some conclusions are drawn. The discussion is based on a variety of sources including MAF, Reserve Bank, Treasury, AERU and private economic reports and data. A considerable part of the material was also obtained from personal correspondence and interviews with people directly involved in the finance industry. The views expressed are, of course those of the authors