1,674 research outputs found
Manipulating the frequency entangled states by acoustic-optical-modulator
In this paper, we describe how to realize conditional frequency entanglement
swapping and to produce probabilisticly a three-photon frequency entangled
state from two pairs of frequency entangled states by using an
Acoustic-Optical-Modulator. Both schemes are very simple and may be
implementable in practice.Comment: 11 pages,3 ps figures, to appear in Phys Rev
Transverse azimuthal dephasing of vortex spin wave in a hot atomic gas
Optical fields with orbital angular momentum (OAM) interact with medium have
many remarkable properties with its unique azimuthal phase, showing many
potential applications in high capacity information processing, high precision
measurement etc. The dephasing mechanics of optical fields with OAM in an
interface between light and matter plays a vital role in many areas of physics.
In this work, we study the transverse azimuthal dephasing of OAM spin wave in a
hot atomic gas via OAM storage. The transverse azimuthal phase difference
between the control and probe beams is mapped onto the spin wave, which
essentially results in dephasing of atomic spin wave. The dephasing of OAM spin
wave can be controlled by the parameters of OAM topological charge and beam
waist. Our results are helpful for studying OAM light interaction with matter,
maybe hold a promise in OAM-based quantum information processing.Comment: 11 pages, 4 figures, original manuscript, comments welcom
Experimental generation of tripartite telecom photons via an atomic ensemble and a nonlinear waveguide
Non-classical multi-photon and number states attracts many people because of
their wide applications in fundamental quantum mechanics tests, quantum
metrology and quantum computation, therefore it is a longstanding aim to
generate such states experimentally. Here, we prepare photon triplets by using
the spontaneously Raman scattering process in a hot atomic ensemble cascaded by
the spontaneous parametric down conversion process in a periodical poled
nonlinear waveguide, the strong temporal correlations of these three photons
are observed. Our experiment represents the first combination of the different
order nonlinear processes and different physical systems, showing the
feasibility of such composite system in this research direction. In addition,
the all photons in the prepared genuine triplet are in telecom band make them
be suitable for long-distance quantum communication in optical fibre.Comment: This is a draft, comments welcome
Experimental nonlocal steering of Bohmian trajectories
Interpretations of quantum mechanics (QM), or proposals for underlying
theories, that attempt to present a definite realist picture, such as Bohmian
mechanics, require strong non-local effects. Naively, these effects would
violate causality and contradict special relativity. However if the theory
agrees with QM the violation cannot be observed directly. Here, we demonstrate
experimentally such an effect: we steer the velocity and trajectory of a
Bohmian particle using a remote measurement. We use a pair of photons and
entangle the spatial transverse position of one with the polarization of the
other. The first photon is sent to a double-slit-like apparatus, where its
trajectory is measured using the technique of Weak Measurements. The other
photon is projected to a linear polarization state. The choice of polarization
state, and the result, steer the first photon in the most intuitive sense of
the word. The effect is indeed shown to be dramatic, while being easy to
visualize. We discuss its strength and what are the conditions for it to occur.Comment: 10 pages, 3 figure
Orbital angular momentum-entanglement frequency transducer
Entanglement is a vital resource for realizing many tasks such as
teleportation, secure key distribution, metrology and quantum computations. To
effectively build entanglement between different quantum systems and share
information between them, a frequency transducer to convert between quantum
states of different wavelengths while retaining its quantum features is
indispensable. Information encoded in the photons orbital angular momentum OAM
degrees of freedom is preferred in harnessing the information carrying capacity
of a single photon because of its unlimited dimensions. A quantum transducer,
which operates at wavelengths from 1558.3 nm to 525 nm for OAM qubits,
OAMpolarization hybrid entangled states, and OAM entangled states, is reported
for the first time. Nonclassical properties and entanglements are demonstrated
following the conversion process by performing quantum tomography,
interference, and Bell inequality measurements. Our results demonstrate the
capability to create an entanglement link between different quantum systems
operating in photons OAM degrees of freedoms, which will be of great importance
in building a high capacity OAM quantum network.Comment: under review in PRL, comments are welco
Extra-cavity-enhanced difference-frequency generation at 1.63 {\mu}m
A 1632-nm laser has highly important applications in interfacing the
wavelength of rubidium-based quantum memories (795 nm) and the telecom band
(typically 1550 nm) by frequency conversion in three-wave mixing processes. A
1632-nm laser source based on pump-enhanced difference frequency generation is
demonstrated. It has 300 mW of output power, in agreement with simulations, and
a 55% quantum efficiency. An average power fluctuation of 0.51% over one hour
was observed, and 200-kHz linewidth was measured using a delayed
self-heterodyne method.Comment: 7 pages, 5 figures, accepted by Journal of the Optical Society of
America
Indirect precise angular control using four-wave mixing
Here we show indirect precise angular control using a four-wave mixing (FWM)
process. This was performed with a superposition of light with orbital angular
momentum (OAM) in an M-Type configuration of a hot 85Rb atomic ensemble. A
gear-shaped interference pattern is observed at FWM light with a donut-shaped
input signal. The gear could be rotated and is controlled through the change of
the polarization of the pump laser. Our experimental results that are based on
nonlinear coherent interactions have applications in image processing and
precise angular control.Comment: Accepted by Applied Physics Letter
Revealing photons behaviors in a birefringent interferometer
The interferometer is one of the most important devices for revealing the
nature of light and for precision optical metrology. Though lots of experiments
were performed for probing photons behaviors in various configurations, a
complete study of photons behavior in a birefringent interferometer has not
ever been performed. Based on an environmental turbulence immune Mach-Zehnder
interferometer, tunable photonic beatings by rotating a birefringent crystal
versus the temperature of the crystal for both single-photon and two-photon are
observed. Furthermore, the two-photon interference fringes beat two times
faster than the single-photon interference fringes. This beating effect is used
to determine the thermal dispersion coefficients of the two principal
refractive axes with a single measurement, the two-photon interference shows
super-resolution and high sensitivity. Obvious differences between two-photon
and single photon interference are also revealed in an unbalanced situations.
In addition, influences of the photon bandwidth to the beating behaviors that
come from polarization-dependent decoherence are also investigated. Our
findings will be important for better understanding the behavior of two-photon
interference in a birefringent interferometer and for precision optical
metrology with quantum enhancement.Comment: 13 pages, 5 figures. accepted in PR
Nonlinear frequency conversion and manipulation of vector beams in a Sagnac loop
Vector beams (VBs) are widely investigated for its special intensity and
polarization distributions, which is useful for optical micromanipulation,
optical micro-fabrication, optical communication, and single molecule imaging.
To date, it is still a challenge to realize nonlinear frequency conversion
(NFC) and manipulation of such VBs because of the polarization sensitivity in
most of nonlinear processes. Here, we report an experimental realization of NFC
and manipulation of VBs which can be used to expand the available frequency
band. The main idea of our scheme is to introduce a Sagnac loop to solve the
polarization dependence of NFC in nonlinear crystals. Furthermore, we find that
a linearly polarized vector beam should be transformed to an exponential form
before performing the NFC. The experimental results are well agree with our
theoretical model. The present method is also applicable to other wave bands
and second order nonlinear processes, and may also be generalized to the
quantum regime for single photons.Comment: 8 pages, 3 figure
Topological charge independent frequency conversion of twisted light
Light with orbital angular momentum (OAM), or twisted light, is widely
investigated in the fields of optical communications, quantum information
science and nonlinear optics by harnessing its unbounded dimension. For
light-matter interacting with twisted light like quantum memory and nonlinear
frequency conversion, efficiencies in these processes are usually decreasing
exponentially with topological charges, which severely degrades the fidelity of
the output states. Here we conceive and develop a method to eliminate the
dependence of conversion efficiency on topological charges in second harmonic
generation (SHG) process by utilizing a special designed image technique. The
independence of SHG conversion efficiency on topological charge is verified for
different topological charges, this independence is valid for various pump
power. This method can be generalized to other light matter interaction
processes and will revolute the field of light matter interaction with twisted
light to achieve higher efficiency and higher fidelity.Comment: 5 pages, 3 figures, comments are welcom
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