15 research outputs found
Classical Bound for Mach-Zehnder Super-Resolution
The employment of path entangled multiphoton states enables measurement of
phase with enhanced precision. It is common practice to demonstrate the unique
properties of such quantum states by measuring super-resolving oscillations in
the coincidence rate of a Mach-Zehnder interferometer. Similar oscillations,
however, have also been demonstrated in various configurations using classical
light only; making it unclear what, if any, are the classical limits of this
phenomenon. Here we derive a classical bound for the visibility of
super-resolving oscillations in a Mach-Zehnder. This provides an easy to apply,
fundamental test of non-classicality. We apply this test to experimental
multiphoton coincidence measurements obtained using photon number resolving
detectors. Mach-Zehnder super-resolution is found to be a highly distinctive
quantum effect.Comment: 4 pages, 4 figure, Comments welcom
Spectral Polarization and Spectral Phase Control of Time and Energy Entangled Photons
We demonstrate a scheme to spectrally manipulate a collinear, continuous
stream of time and energy entangled photons to generate beamlike,
bandwidth-limited fuxes of polarization-entangled photons with
nearly-degenerate wavelengths. Utilizing an ultrashort-pulse shaper to control
the spectral phase and polarization of the photon pairs, we tailor the shape of
the Hong-Ou-Mandel interference pattern, demonstrating the rules that govern
the dependence of this interference pattern on the spectral phases of the
photons. We then use the pulse shaper to generate all four polarization Bell
states. The singlet state generated by this scheme forms a very robust
decoherence-free subspace, extremely suitable for long distance fiber-optics
based quantum communication.Comment: 5 pages, 3 figure
Sub-Rayleigh lithography using high flux loss-resistant entangled states of light
Quantum lithography achieves phase super-resolution using fragile,
experimentally challenging entangled states of light. We propose a scalable
scheme for creating features narrower than classically achievable, with reduced
use of quantum resources and consequently enhanced resistance to loss. The
scheme is an implementation of interferometric lithography using a mixture of
an SPDC entangled state with intense classical coherent light. We measure
coincidences of up to four photons mimicking multiphoton absorption. The
results show a narrowing of the interference fringes of up to 30% with respect
to the best analogous classical scheme using only 10% of the non-classical
light required for creating NOON states.Comment: 5 pages, 4 figure
Void Formation and Roughening in Slow Fracture
Slow crack propagation in ductile, and in certain brittle materials, appears
to take place via the nucleation of voids ahead of the crack tip due to plastic
yields, followed by the coalescence of these voids. Post mortem analysis of the
resulting fracture surfaces of ductile and brittle materials on the m-mm
and the nm scales respectively, reveals self-affine cracks with anomalous
scaling exponent in 3-dimensions and in
2-dimensions. In this paper we present an analytic theory based on the method
of iterated conformal maps aimed at modelling the void formation and the
fracture growth, culminating in estimates of the roughening exponents in
2-dimensions. In the simplest realization of the model we allow one void ahead
of the crack, and address the robustness of the roughening exponent. Next we
develop the theory further, to include two voids ahead of the crack. This
development necessitates generalizing the method of iterated conformal maps to
include doubly connected regions (maps from the annulus rather than the unit
circle). While mathematically and numerically feasible, we find that the
employment of the stress field as computed from elasticity theory becomes
questionable when more than one void is explicitly inserted into the material.
Thus further progress in this line of research calls for improved treatment of
the plastic dynamics.Comment: 15 pages, 20 figure