131 research outputs found
On Visibility in the Afshar Two-Slit Experiment
A modified version of Young's experiment by Shahriar Afshar indirectly
reveals the presence of a fully articulated interference pattern prior to the
post-selection of a particle in a "which-slit" basis. While this experiment
does not constitute a violation of Bohr's Complementarity Principle as claimed
by Afshar, both he and many of his critics incorrectly assume that a commonly
used relationship between visibility parameter V and "which-way" parameter K
has crucial relevance to his experiment. It is argued here that this
relationship does not apply to this experimental situation and that it is wrong
to make any use of it in support of claims for or against the bearing of this
experiment on Complementarity.Comment: Final version; to appear in Foundations of Physic
On the efficiency of quantum lithography
Quantum lithography promises, in principle, unlimited feature resolution,
independent of wavelength. However, in the literature at least two different
theoretical descriptions of quantum lithography exist. They differ in to which
extent they predict that the photons retain spatial correlation from generation
to the absorption, and while both predict the same feature size, they differ
vastly in predicting how efficiently a quantum lithographic pattern can be
exposed.
Until recently, essentially all experiments reported have been performed in
such a way that it is difficult to distinguish between the two theoretical
explanations. However, last year an experiment was performed which gives
different outcomes for the two theories. We comment on the experiment and show
that the model that fits the data unfortunately indicates that the trade-off
between resolution and efficiency in quantum lithography is very unfavourable.Comment: 19 pages, extended version including a thorough mathematical
derivatio
Reply to Comments of Steuernagel on the Afshar's Experiment
We respond to criticism of our paper "Paradox in Wave-Paricle Duality for
Non-Perturbative Measurements". We disagree with Steuernagel's derivation of
the visibility of the Afshar experiment. To calculate the fringe visibility,
Steuernagel utilizes two different experimental situations, i.e. the wire grid
in the pattern minima and in the pattern maxima. In our assessment, this
proceduere cannot lead to the correct result for the complementarity properties
of wave-particle in one particular experimental set-up
Optical Lenses for Atomic Beams
Superpositions of paraxial laser beam modes to generate atom-optical lenses
based on the optical dipole force are investigated theoretically. Thin, wide,
parabolic, cylindrical and circular atom lenses with numerical apertures much
greater than those reported in the literature to date can be synthesized. This
superposition approach promises to make high quality atom beam imaging and
nano-deposition feasible.Comment: 10 figure
Synthesis and Characterization of New Polymers from Adenopus breviflorus benth oil, Styrene and Divinyl benzene by Cationic Polymerization
A variety of new polymers ranging from soft to hard plastics were prepared by cationic polymerization of Adenopus breviflorus oil with styrene and divinyl benzene initiated by modified boron trifluoride etherate. The fully cured thermosets were found to contain between 78- 92% cross linked materials possessing crosslink densities of between 2.39 x 103 to 2.09 x 104 mol/m3 and glass transition temperatures of 12 – 800C. The tensile moduli of the materials ranged from 1.47 to 404MPa, the ultimate tensile stress varied from 0.18 to 7.78MPa and the elongation at break varied between 2 and 34%. Depending on composition, some of the materials possessed good damping and shape memory properties. Overall the newly prepared materials from Adenopus breviflorus oil hold a lot of promise as new polymeric materials
Spectrum of light scattering from an extended atomic wave packet
The spectrum of the light scattered from an extended atomic wave packet is
calculated. For a wave packet consisting of two spatially separated peaks
moving on parallel trajectories, the spectrum contains Ramsey-like fringes that
are sensitive to the phase difference between the two components of the wave
packet. Using this technique, one can establish the mutual coherence of the two
components of the wave packet without recombining them.Comment: 4 page
Approaching the Heisenberg limit with two mode squeezed states
Two mode squeezed states can be used to achieve Heisenberg limit scaling in
interferometry: a phase shift of can be
resolved. The proposed scheme relies on balanced homodyne detection and can be
implemented with current technology. The most important experimental
imperfections are studied and their impact quantified.Comment: 4 pages, 7 figure
Generalised Hong-Ou-Mandel Experiments with Bosons and Fermions
The Hong-Ou-Mandel (HOM) dip plays an important role in recent linear optics
experiments. It is crucial for quantum computing with photons and can be used
to characterise the quality of single photon sources and linear optics setups.
In this paper, we consider generalised HOM experiments with bosons or
fermions passing simultaneously through a symmetric Bell multiport beam
splitter. It is shown that for even numbers of bosons, the HOM dip occurs
naturally in the coincidence detection in the output ports. In contrast,
fermions always leave the setup separately exhibiting perfect coincidence
detection. Our results can be used to verify or employ the quantum statistics
of particles experimentally.Comment: 11 pages, 2 figures, more references adde
How to determine a quantum state by measurements: The Pauli problem for a particle with arbitrary potential
The problem of reconstructing a pure quantum state ¿¿> from measurable quantities is considered for a particle moving in a one-dimensional potential V(x). Suppose that the position probability distribution ¿¿(x,t)¿2 has been measured at time t, and let it have M nodes. It is shown that after measuring the time evolved distribution at a short-time interval ¿t later, ¿¿(x,t+¿t)¿2, the set of wave functions compatible with these distributions is given by a smooth manifold M in Hilbert space. The manifold M is isomorphic to an M-dimensional torus, TM. Finally, M additional expectation values of appropriately chosen nonlocal operators fix the quantum state uniquely. The method used here is the analog of an approach that has been applied successfully to the corresponding problem for a spin system
Creation of maximally entangled photon-number states using optical fiber 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.Comment: 4 pages, 1 figure. REVTeX4. Replaced with published versio
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