4,073 research outputs found
Nonclassical effects in two-photon interference experiments: event-by-event simulations
It is shown that both the visibility predicted for
two-photon interference experiments with two independent
sources\textcolor{black}{, like the Hanbury Brown-Twiss experiment,} and the
visibility predicted for two-photon interference experiments
with a parametric down-conversion source\textcolor{black}{, like the
Ghosh-Mandel experiment,} can be explained \textcolor{black}{by a discrete
event simulation. This simulation approach reproduces the statistical
distributions of wave theory not by requiring the knowledge of the solution of
the wave equation of the whole system but by generating detection events
one-by-one according to an unknown distribution.} There is thus no need to
invoke quantum theory to explain the so-called nonclassical effects in the
interference of signal and idler photons in parametric down conversion. Hence,
a revision of the commonly accepted criterion of the nonclassical nature of
light\textcolor{black}{, ,} is called for.Comment: arXiv admin note: substantial text overlap with arXiv:1208.2368,
arXiv:1006.172
Compressively characterizing high-dimensional entangled states with complementary, random filtering
The resources needed to conventionally characterize a quantum system are
overwhelmingly large for high- dimensional systems. This obstacle may be
overcome by abandoning traditional cornerstones of quantum measurement, such as
general quantum states, strong projective measurement, and assumption-free
characterization. Following this reasoning, we demonstrate an efficient
technique for characterizing high-dimensional, spatial entanglement with one
set of measurements. We recover sharp distributions with local, random
filtering of the same ensemble in momentum followed by position---something the
uncertainty principle forbids for projective measurements. Exploiting the
expectation that entangled signals are highly correlated, we use fewer than
5,000 measurements to characterize a 65, 536-dimensional state. Finally, we use
entropic inequalities to witness entanglement without a density matrix. Our
method represents the sea change unfolding in quantum measurement where methods
influenced by the information theory and signal-processing communities replace
unscalable, brute-force techniques---a progression previously followed by
classical sensing.Comment: 13 pages, 7 figure
Experimental characterization of the COndensation PArticle counting System for high altitude aircraft-borne application
A characterization of the ultra-fine aerosol particle counter COPAS (COndensation PArticle counting System) for operation on board the Russian high altitude research aircraft M-55 Geophysika is presented. The COPAS instrument consists of an aerosol inlet and two dual-channel continuous flow Condensation Particle Counters (CPCs) operated with the chlorofluorocarbon FC-43. It operates at pressures between 400 and 50 hPa for aerosol detection in the particle diameter (dp) range from 6 nm up to 1 micro m. The aerosol inlet, designed for the M-55, is characterized with respect to aspiration, transmission, and transport losses. The experimental characterization of counting efficiencies of three CPCs yields dp50 (50% detection particle diameter) of 6 nm, 11 nm, and 15 nm at temperature differences (DeltaT) between saturator and condenser of 17°C, 30°C, and 33°C, respectively. Non-volatile particles are quantified with a fourth CPC, with dp50=11 nm. It includes an aerosol heating line (250°C) to evaporate H2SO4-H2O particles of 11 nm<dp<200 nm at pressures between 70 and 300 hPa. An instrumental in-flight inter-comparison of the different COPAS CPCs yields correlation coefficients of 0.996 and 0.985. The particle emission index for the M-55 in the range of 1.4–8.4×10 16 kg -1 fuel burned has been estimated based on measurements of the Geophysika's own exhaust
The GRA Beam-Splitter Experiments and Particle-Wave Duality of Light
Grangier, Roger and Aspect (GRA) performed a beam-splitter experiment to
demonstrate the particle behaviour of light and a Mach-Zehnder interferometer
experiment to demonstrate the wave behaviour of light. The distinguishing
feature of these experiments is the use of a gating system to produce near
ideal single photon states. With the demonstration of both wave and particle
behaviour (in two mutually exclusive experiments) they claim to have
demonstrated the dual particle-wave behaviour of light and hence to have
confirmed Bohr's principle of complementarity. The demonstration of the wave
behaviour of light is not in dispute. But we want to demonstrate, contrary to
the claims of GRA, that their beam-splitter experiment does not conclusively
confirm the particle behaviour of light, and hence does not confirm
particle-wave duality, nor, more generally, does it confirm complementarity.
Our demonstration consists of providing a detailed model based on the Causal
Interpretation of Quantum Fields (CIEM), which does not involve the particle
concept, of GRA's which-path experiment. We will also give a brief outline of a
CIEM model for the second, interference, GRA experiment.Comment: 24 pages, 4 figure
Delayed-choice gedanken experiments and their realizations
The wave-particle duality dates back to Einstein's explanation of the
photoelectric effect through quanta of light and de Broglie's hypothesis of
matter waves. Quantum mechanics uses an abstract description for the behavior
of physical systems such as photons, electrons, or atoms. Whether quantum
predictions for single systems in an interferometric experiment allow an
intuitive understanding in terms of the particle or wave picture, depends on
the specific configuration which is being used. In principle, this leaves open
the possibility that quantum systems always either behave definitely as a
particle or definitely as a wave in every experimental run by a priori adapting
to the specific experimental situation. This is precisely what is tried to be
excluded by delayed-choice experiments, in which the observer chooses to reveal
the particle or wave character -- or even a continuous transformation between
the two -- of a quantum system at a late stage of the experiment. We review the
history of delayed-choice gedanken experiments, which can be traced back to the
early days of quantum mechanics. Then we discuss their experimental
realizations, in particular Wheeler's delayed choice in interferometric setups
as well as delayed-choice quantum erasure and entanglement swapping. The latter
is particularly interesting, because it elevates the wave-particle duality of a
single quantum system to an entanglement-separability duality of multiple
systems
Analytical techniques: A compilation
A compilation, containing articles on a number of analytical techniques for quality control engineers and laboratory workers, is presented. Data cover techniques for testing electronic, mechanical, and optical systems, nondestructive testing techniques, and gas analysis techniques
Event-by-event simulation of quantum phenomena
A discrete-event simulation approach is reviewed that does not require the
knowledge of the solution of the wave equation of the whole system, yet
reproduces the statistical distributions of wave theory by generating detection
events one-by-one. The simulation approach is illustrated by applications to a
two-beam interference experiment and two Bell test experiments, an
Einstein-Podolsky-Rosen- Bohm experiment with single photons employing
postselection for pair identification and a single-neutron Bell test
interferometry experiment with nearly 100% detection efficiency
Event-based simulation of quantum physics experiments
We review an event-based simulation approach which reproduces the statistical
distributions of wave theory not by requiring the knowledge of the solution of
the wave equation of the whole system but by generating detection events
one-by-one according to an unknown distribution. We illustrate its
applicability to various single photon and single neutron interferometry
experiments and to two Bell test experiments, a single-photon
Einstein-Podolsky-Rosen experiment employing post-selection for photon pair
identification and a single-neutron Bell test interferometry experiment with
nearly detection efficiency.Comment: Lectures notes of the Advanced School on Quantum Foundations and Open
Quantum Systems, Jo\~ao Pessoa, Brazil, July 2012, edited by T. M.
Nieuwenhuizen et al, World Scientific, to appea
Characterization of the MIC photon counting detector
A new photon counting detector, MIC, has been developed at UCL and is an enhanced performance version of the highly successful IPCS in use at a number of large ground based optical telescopes throughout the world. This detector is light weight, compact and has a low power consumption making it suitable for Space as well as ground based applications. In particular, a prototype version of the MIC detector, XMM-MIC, has been developed for the Optical Monitor (OM) that is to be included in the ESA 'Horizon 2000' X-Ray Multi-Mirror Mission (XMM). In this thesis details of the detector system are given along with the theory of operation. A description of those components which limit the detector performance in terms of resolution, image quality, dynamic range and detective quantum efficiency is presented. The performance is characterized both under laboratory and telescope conditions and compared against theoretical data. In addition, computer simulations have been used to compare the detector performance with other types of photon counting detector thus defining the scientific applications to which MIC can most usefully be put. Finally, future developments of the MIC detector are discussed in terms of both Space and ground based applications. Within the context of this thesis the author has been responsible for the theoretical modelling of a number of detector characteristics, analysis of data and its comparison with theoretical predictions. Computer models were also developed by the author in order to simulate the dynamic range performance of other types of photon counting detector. In addition the author has contributed towards the software development of the detector system and participated fully in all the observing and laboratory trials
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