1,928 research outputs found
Describing two-mode squeezed-light experiments without two-mode entanglement or squeezing
In a recent work [Phys. Rev. A , 053723 (2020)] we have shown
that experiments that produce and characterize single-mode light squeezing can
be explained in a way where no single-mode squeezed light state is produced in
the setup. Here we apply the same ideas to demonstrate that experiments that
produce and characterize two-mode light squeezing can also be explained without
the production of two-mode squeezed light states. In particular, we show that
there is no entanglement between the signal and idler "twin beam" modes. This
fact may be surprising, since this setup is frequently used to implement
entangled-based quantum information protocols such as quantum teleportation.
Our work brings an alternative view of the phenomenon. We generalize the Luis
and S\'anchez-Soto's two-mode relative phase distribution [Phys. Rev. A
, 495 (1996)] to treat four modes, showing that a general physical
explanation for the noise reduction in the experiments is a better definition
of a phase relation among the four involved optical modes: Signal, idler, and
two local oscillators.Comment: 7 pages, 3 figure
Interferometric sensing of the tilt angle of a Gaussian beam
We investigate interferometric techniques to estimate the deflection angle of
an optical beam and compare them to the direct detection of the beam
deflection. We show that quantum metrology methods lead to a unifying treatment
for both single photons and classical fields. Using the Fisher information to
assess the precision limits of the interferometric schemes, we show that the
precision can be increased by exploiting the initial transverse displacement of
the beam. This gain, which is present for both Sagnac and Mach-Zehnder-like
configurations, can be considerable when compared to non-interferometric
methods. In addition to the fundamental increase in precision, the
interferometric schemes have the technical advantage that (i) the precision
limits can be saturated by a sole polarization measurement on the field, and
that (ii) the detection system can be placed at any longitudinal position along
the beam. We also consider position-dependent polarization measurements, and
show that in this case the precision increases with the propagation distance,
as well as the initial transverse displacement.Comment: Comments are welcom
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