3,174 research outputs found
Theoretical investigation of moir\'e patterns in quantum images
Moir\'e patterns are produced when two periodic structures with different
spatial frequencies are superposed. The transmission of the resulting structure
gives rise to spatial beatings which are called moir\'e fringes. In classical
optics, the interest in moir\'e fringes comes from the fact that the spatial
beating given by the frequency difference gives information about details(high
spatial frequency) of a given spatial structure. We show that moir\'e fringes
can also arise in the spatial distribution of the coincidence count rate of
twin photons from the parametric down-conversion, when spatial structures with
different frequencies are placed in the path of each one of the twin beams. In
other words,we demonstrate how moir\'e fringes can arise from quantum images
Conservation of Orbital Angular Momentum in Stimulated Down-Conversion
We report on an experiment demonstrating the conservation of orbital angular
momentum in stimulated down-conversion. The orbital angular momentum is not
transferred to the individual beams of the spontaneous down-conversion, but it
is conserved when twin photons are taken individually. We observe the
conservation law for an individual beam of the down-conversion through
cavity-free stimulated emission.Comment: Submitted for publication in Phys. Rev. Let
Phase detection at the quantum limit with multi-photon Mach-Zehnder interferometry
We study a Mach-Zehnder interferometer fed by a coherent state in one input
port and vacuum in the other. We explore a Bayesian phase estimation strategy
to demonstrate that it is possible to achieve the standard quantum limit
independently from the true value of the phase shift and specific assumptions
on the noise of the interferometer. We have been able to implement the protocol
using parallel operation of two photon-number-resolving detectors and
multiphoton coincidence logic electronics at the output ports of a
weakly-illuminated Mach-Zehnder interferometer. This protocol is unbiased and
saturates the Cramer-Rao phase uncertainty bound and, therefore, is an optimal
phase estimation strategy.Comment: 4 pages, 5 figures replaced fig. 1 to correct graphics bu
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