16,792 research outputs found
Twisted Light Transmission over 143 kilometers
Spatial modes of light can potentially carry a vast amount of information,
making them promising candidates for both classical and quantum communication.
However, the distribution of such modes over large distances remains difficult.
Intermodal coupling complicates their use with common fibers, while free-space
transmission is thought to be strongly influenced by atmospheric turbulence.
Here we show the transmission of orbital angular momentum modes of light over a
distance of 143 kilometers between two Canary Islands, which is 50 times
greater than the maximum distance achieved previously. As a demonstration of
the transmission quality, we use superpositions of these modes to encode a
short message. At the receiver, an artificial neural network is used for
distinguishing between the different twisted light superpositions. The
algorithm is able to identify different mode superpositions with an accuracy of
more than 80% up to the third mode order, and decode the transmitted message
with an error rate of 8.33%. Using our data, we estimate that the distribution
of orbital angular momentum entanglement over more than 100 kilometers of free
space is feasible. Moreover, the quality of our free-space link can be further
improved by the use of state-of-the-art adaptive optics systems.Comment: 12 pages, 4 figure
Free-space propagation of high dimensional structured optical fields in an urban environment
Spatially structured optical fields have been used to enhance the functionality of a wide variety of systems that use
light for sensing or information transfer. As higher-dimensional modes become a solution of choice in optical
systems, it is important to develop channel models that suitably predict the effect of atmospheric turbulence on
these modes. We investigate the propagation of a set of orthogonal spatial modes across a free-space channel
between two buildings separated by 1.6 km. Given the circular geometry of a common optical lens, the orthogonal
mode set we choose to implement is that described by the Laguerre-Gaussian (LG) field equations. Our study focuses
on the preservation of phase purity, which is vital for spatial multiplexing and any system requiring full quantumstate
tomography. We present experimental data for the modal degradation in a real urban environment and draw a
comparison to recognized theoretical predictions of the link. Our findings indicate that adaptations to channel
models are required to simulate the effects of atmospheric turbulence placed on high-dimensional structured
modes that propagate over a long distance. Our study indicates that with mitigation of vortex splitting, potentially
through precorrection techniques, one could overcome the challenges in a real point-to-point free-space channel in
an urban environment
Complete experimental toolbox for alignment-free quantum communication
Quantum communication employs the counter-intuitive features of quantum
physics to perform tasks that are im- possible in the classical world. It is
crucial for testing the foundations of quantum theory and promises to rev-
olutionize our information and communication technolo- gies. However, for two
or more parties to execute even the simplest quantum transmission, they must
establish, and maintain, a shared reference frame. This introduces a
considerable overhead in communication resources, par- ticularly if the parties
are in motion or rotating relative to each other. We experimentally demonstrate
how to circumvent this problem with the efficient transmission of quantum
information encoded in rotationally invariant states of single photons. By
developing a complete toolbox for the efficient encoding and decoding of
quantum infor- mation in such photonic qubits, we demonstrate the fea- sibility
of alignment-free quantum key-distribution, and perform a proof-of-principle
alignment-free entanglement distribution and violation of a Bell inequality.
Our scheme should find applications in fundamental tests of quantum mechanics
and satellite-based quantum communication.Comment: Main manuscript: 7 pages, 3 figures; Supplementary Information: 7
pages, 3 figure
Determination of optical technology experiments for a satellite
Optical technology experiments for satellite - communications, acquisition, tracking, lasers, photometry, and atmospheric
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