499 research outputs found
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
Entanglement-enhanced measurement of a completely unknown phase
The high-precision interferometric measurement of an unknown phase is the
basis for metrology in many areas of science and technology. Quantum
entanglement provides an increase in sensitivity, but present techniques have
only surpassed the limits of classical interferometry for the measurement of
small variations about a known phase. Here we introduce a technique that
combines entangled states with an adaptive algorithm to precisely estimate a
completely unspecified phase, obtaining more information per photon that is
possible classically. We use the technique to make the first ab initio
entanglement-enhanced optical phase measurement. This approach will enable
rapid, precise determination of unknown phase shifts using interferometry.Comment: 6 pages, 4 figure
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