5,074 research outputs found
Probabilistic Quantum Logic Operations Using Polarizing Beam Splitters
It has previously been shown that probabilistic quantum logic operations can
be performed using linear optical elements, additional photons (ancilla), and
post-selection based on the output of single-photon detectors. Here we describe
the operation of several quantum logic operations of an elementary nature,
including a quantum parity check and a quantum encoder, and we show how they
can be combined to implement a controlled-NOT (CNOT) gate. All of these gates
can be constructed using polarizing beam splitters that completely transmit one
state of polarization and totally reflect the orthogonal state of polarization,
which allows a simple explanation of each operation. We also describe a
polarizing beam splitter implementation of a CNOT gate that is closely
analogous to the quantum teleportation technique previously suggested by
Gottesman and Chuang [Nature 402, p.390 (1999)]. Finally, our approach has the
interesting feature that it makes practical use of a quantum-eraser technique.Comment: 9 pages, RevTex; Submitted to Phys. Rev. A; additional references
inlcude
Polarization Drift Channel Model for Coherent Fibre-Optic Systems
A theoretical framework is introduced to model the dynamical changes of the
state of polarization during transmission in coherent fibre-optic systems. The
model generalizes the one-dimensional phase noise random walk to higher
dimensions, accounting for random polarization drifts, emulating a random walk
on the Poincar\'e sphere, which has been successfully verified using
experimental data. The model is described in the Jones, Stokes and real
four-dimensional formalisms, and the mapping between them is derived. Such a
model will be increasingly important in simulating and optimizing future
systems, where polarization-multiplexed transmission and sophisticated digital
signal processing will be natural parts. The proposed polarization drift model
is the first of its kind as prior work either models polarization drift as a
deterministic process or focuses on polarization-mode dispersion in systems
where the state of polarization does not affect the receiver performance. We
expect the model to be useful in a wide-range of photonics applications where
stochastic polarization fluctuation is an issue.Comment: 15 pages, 4 figure
Impulsive solar X-ray bursts. 3: Polarization and directivity of bremsstrahlung radiation from a beam of electrons directed toward the photosphere
The spectrum, directivity and state of polarization is presented of the bremsstrahlung radiation expected from a beam of high energy electrons spiraling along radial magnetic field lines toward the photosphere. The results are used for calculation of the characteristics of the reflected plus direct flux
Conical refraction healing after partially blocking the input beam
In conical refraction, when a focused Gaussian beam passes along one of the
optic axes of a biaxial crystal it is transformed into a pair of concentric
bright rings at the focal plane. We demonstrate both theoretically and
experimentally that this transformation is hardly affected by partially
blocking the Gaussian input beam with an obstacle. We analyze the influence of
the size of the obstruction both on the transverse intensity pattern of the
beam and on its state of polarization, which is shown to be very robust
Gravity and handedness of photons
Vacuum fluctuations of quantum fields are altered in presence of a strong
gravitational background, with important physical consequences. We argue that a
non-trivial spacetime geometry can act as an optically active medium for
quantum electromagnetic radiation, in such a way that the state of polarization
of radiation changes in time, even in the absence of electromagnetic sources.
This is a quantum effect, and is a consequence of an anomaly related to the
classical invariance under electric-magnetic duality rotations in Maxwell
theory.Comment: First Award in the 2017 Essay Competition of the Gravity Research
Foundatio
Coherent scattering of a Multiphoton Quantum Superposition by a Mirror-BEC
We present the proposition of an experiment in which the multiphoton quantum
superposition consisting of N= 10^5 particles generated by a quantum-injected
optical parametric amplifier (QI-OPA), seeded by a single-photon belonging to
an EPR entangled pair, is made to interact with a Mirror-BEC shaped as a Bragg
interference structure. The overall process will realize a Macroscopic Quantum
Superposition (MQS) involving a microscopic single-photon state of polarization
entangled with the coherent macroscopic transfer of momentum to the BEC
structure, acting in space-like separated distant places.Comment: 4 pages, 4 figure
A three-dimensional degree of polarization based on Rayleigh scattering
A measure of the degree of polarization for the three-dimensional
polarization matrix (coherence matrix) of an electromagnetic field is proposed,
based on Rayleigh scattering. The degree of polarization, due to dipole
scattering of the three-dimensional state of polarization, is averaged over all
scattering directions. This gives a well-defined purity measure, which, unlike
other proposed measures of the three-dimensional degree of polarization, is not
a unitary invariant of the matrix. This is demonstrated and discussed for
several examples, including a partially polarized transverse beam.Comment: 17 pages, 3 figures. OSA styl
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