scholarly journals Effects of Oceanic Turbulence on Orbital Angular Momenta of Optical Communications

2020 ◽  
Vol 8 (11) ◽  
pp. 869
Author(s):  
Shuang Zhai ◽  
Yun Zhu ◽  
Yixin Zhang ◽  
Zhengda Hu
Keyword(s):  
Dissipation Rate ◽  
Quantum Coherence ◽  
Single Photon ◽  
Beam Width ◽  
Communication Performance ◽  
Oceanic Turbulence ◽  
Angular Momenta ◽  
Optimal Beam ◽  
Lower Temperature ◽  
Inner Scale

The propagation properties of Laguerre-Gaussian beams in oceanic turbulence are investigated for both single-photon and biphoton cases. For single-photon communication, the channel capacity and trace distance are employed, both of which effectively reveal the communication performance via different viewpoints. For the biphoton case, we consider distributions of quantum resources including entanglement and quantum coherence. Turbulence conditions with a larger inner-scale and anisotropic factors, higher dissipation rate of kinetic energy, lower dissipation rate of the mean-squared temperature, and lower temperature-salinity contribution ratio combined with longer wavelength and an appropriate range of optimal beam width are beneficial to communication performances. Our results provide theoretical significance to improve the orbital-angular-momentum communication via oceanic turbulence.

scholarly journals Propagation Properties of an Off-Axis Hollow Gaussian-Schell Model Vortex Beam in Anisotropic Oceanic Turbulence

2021 ◽  
Vol 9 (10) ◽  
pp. 1139
Author(s):  
Xinguang Wang ◽  
Le Wang ◽  
Shengmei Zhao
Keyword(s):  
Dissipation Rate ◽  
Beam Width ◽  
Average Intensity ◽  
Vortex Beam ◽  
Oceanic Turbulence ◽  
Beam Characteristic ◽  
Anisotropic Coefficient ◽  
Higher Temperature ◽  
Inner Scale ◽  
Propagation Properties

Based on the extended Huygens–Fresnel principle and the power spectrum of anisotropic oceanic turbulence, the analytical expressions of the average intensity and coherence properties of an off-axis hollow Gaussian-Schell model (OAHGSM) vortex beam propagating through anisotropic oceanic turbulence were derived. The effects of turbulent ocean and beam characteristic parameters on the evolution properties of the OAHGSM vortex beam were analyzed in detail. Our numerical simulation results showed that the OAHGSM vortex beam with a larger position factor is more focusable. Meanwhile, the OAHGSM vortex beam eventually evolves into a Gaussian-like beam after propagating through the anisotropic oceanic turbulent channel. The speed of this process can be accelerated by the decrease of the hollow order, topological charge, beam width, and transverse coherence width of the beam. The results also indicated that the normalized average intensity spreads more greatly and the spectral degree of coherence decays more rapidly for the smaller dissipation rate of the kinetic energy per unit mass of fluid, the smaller anisotropic coefficient, the smaller inner scale factor, the larger dissipation rate of the mean-squared temperature, and the higher temperature–salinity contribution ratio.

scholarly journals Measurement of entropy and quantum coherence properties of two type-I entangled photonic qubits

2021 ◽  
Vol 53 (7) ◽  
Author(s):  
Ali Motazedifard ◽  
Seyed Ahmad Madani ◽  
N. S. Vayaghan
Keyword(s):  
Maximum Likelihood ◽  
Quantum Coherence ◽  
Single Photon ◽  
Bell Inequality ◽  
Bell State ◽  
Von Neumann Entropy ◽  
Entangled State ◽  
Type I ◽  
Variable Theory ◽  
High Brightness

AbstractUsing the type-I SPDC process in BBO nonlinear crystal, we generate a polarization-entangled state near to the maximally-entangled Bell-state with high-visibility (high-brightness) 98.50 ± 1.33% (87.71 ± 4.45%) for HV (DA) basis. We calculate the CHSH version of the Bell inequality, as a nonlocal realism test, and find a strong violation from the classical physics or any hidden variable theory, S = 2.71 ± 0.10. Via measuring the coincidence count rate in the SPDC process, we obtain the quantum efficiency of single-photon detectors around (25.5 ± 3.4)%, which is in good agreement to their manufacturer company. As expected, we verify the linear dependency of the CC rate vs. pump power of input CW-laser, which may yield to find the effective second-order susceptibility crystal. Using the theory of the measurement of qubits, includes a tomographic reconstruction of quantum states due to the linear set of 16 polarization-measurement, together with a maximum-likelihood-technique, which is based on the numerical optimization, we calculate the physical non-negative definite density matrices, which implies on the non-separability and entanglement of prepared state. By having the maximum likelihood density operator, we calculate precisely the entanglement measures such as Concurrence, entanglement of formation, tangle, logarithmic negativity, and different entanglement entropies such as linear entropy, Von-Neumann entropy, and Renyi 2-entropy. Finally, this high-brightness and low-rate entangled photons source can be used for short-range quantum measurements in the Lab.

scholarly journals Observing quantum coherence from photons scattered in free-space

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Shihan Sajeed ◽  
Thomas Jennewein
Keyword(s):  
Free Space ◽  
Quantum Coherence ◽  
Quantum Communication ◽  
Single Photon ◽  
Detector Array ◽  
Line Of Sight ◽  
Background Suppression ◽  
Single Photon Detector ◽  
High Background ◽  
Non Line Of Sight

AbstractQuantum channels in free-space, an essential prerequisite for fundamental tests of quantum mechanics and quantum technologies in open space, have so far been based on direct line-of-sight because the predominant approaches for photon-encoding, including polarization and spatial modes, are not compatible with randomly scattered photons. Here we demonstrate a novel approach to transfer and recover quantum coherence from scattered, non-line-of-sight photons analyzed in a multimode and imaging interferometer for time-bins, combined with photon detection based on a 8 × 8 single-photon-detector-array. The observed time-bin visibility for scattered photons remained at a high 95% over a wide scattering angle range of −450 to +450, while the individual pixels in the detector array resolve or track an image in its field of view of ca. 0.5°. Using our method, we demonstrate the viability of two novel applications. Firstly, using scattered photons as an indirect channel for quantum communication thereby enabling non-line-of-sight quantum communication with background suppression, and secondly, using the combined arrival time and quantum coherence to enhance the contrast of low-light imaging and laser ranging under high background light. We believe our method will instigate new lines for research and development on applying photon coherence from scattered signals to quantum sensing, imaging, and communication in free-space environments.

Refractivity turbulence, inner scale, and eddy dissipation rate observations using a balloon-ring platform

2003 ◽  
Author(s):  
Frank D. Eaton ◽  
Patrick R. Kelly ◽  
Demos T. Kyrazis ◽  
Sheldon D. Stokes
Keyword(s):  
Dissipation Rate ◽  
Inner Scale

Optical Communication Performance of Solitonic Pulses in Weak Oceanic Turbulence

2018 ◽  
Vol 45 (5) ◽  
pp. 0506004
Author(s):  
王阳 Wang Yang ◽  
张鹏 Zhang Peng ◽  
李晓燕 Li Xiaoyan ◽  
王超 Wang Chao ◽  
王大帅 Wang Dashuai ◽  
...  
Keyword(s):  
Optical Communication ◽  
Communication Performance ◽  
Oceanic Turbulence

Influence of the Oceanic Turbulence on Performance of Single Photon Acquisition Probability

2019 ◽  
Vol 56 (24) ◽  
pp. 242702
Author(s):  
聂敏 Nie Min ◽  
赵元 Zhao Yuan ◽  
杨光 Yang Guang ◽  
张美玲 Zhang Meiling ◽  
孙爱晶 Sun Aijing ◽  
...  
Keyword(s):  
Single Photon ◽  
Oceanic Turbulence

scholarly journals Effects of Turbulence on the Vortex Modes Carried by Quasi-Diffracting Free Finite Energy Beam in Ocean

2020 ◽  
Vol 8 (6) ◽  
pp. 458
Author(s):  
Qiyong Liang ◽  
Yixin Zhang ◽  
Dongyu Yang
Keyword(s):  
Gaussian Beam ◽  
Cone Angle ◽  
Wave Structure ◽  
Beam Width ◽  
Finite Energy ◽  
Energy Beam ◽  
Initial Beam ◽  
Oceanic Turbulence ◽  
Wireless Optical Communication ◽  
Ellipticity Parameter

By developing new wave structure function of a beam waves, we derive the transmitting probability of signal vortex modes in oceanic turbulence based on Rytov approximation theory. Applying this transmitting probability of signal vortex modes, we study the influence of oceanic turbulence on the transmittance of the vortex modes carried by Mathieu-Gaussian beam. This model shows the transmitting probability of Mathieu-Gaussian beam with narrow initial beam width, long wavelength, and small ellipticity parameter is higher than the transmitting probability of the signal vortex modes in case of the beam with wide initial beam width, short wavelength, and great ellipticity parameter. Furthermore, when Mathieu-Gaussian beam has a suitable semi-cone angle, the effect of weak-turbulence channel on the transmitting probability of signal vortex modes with different topological charge can be ignored. Mathieu-Gaussian beam is a more suitable carrier for high information channel of underwater wireless optical communication than Laguerre-Gaussian beam.

Multiarrival Kirchhoff beam migration

Geophysics ◽  
2011 ◽  
Vol 76 (5) ◽  
pp. WB109-WB118 ◽  
Author(s):  
Jonathan Liu ◽  
Gopal Palacharla
Keyword(s):  
Model Updating ◽  
Plane Waves ◽  
Beam Width ◽  
Velocity Model ◽  
Model Complexity ◽  
Depth Migration ◽  
Kirchhoff Migration ◽  
Optimal Beam ◽  
Local Plane ◽  
Gaussian Beam Migration

Kirchhoff-type prestack depth migration is the method most popular for outputting offset gathers for velocity-model updating because of its flexibility and efficiency. However, conventional implementations of Kirchhoff migration use only single arrivals. This limits its ability to image complex structures such as subsalt areas. We use the beam methodology to develop a multiarrival Kirchhoff beam migration. The theory and algorithm of our beam migration are analogs to Gaussian beam migration, but we focus on attaining kinematic accuracy and implementation efficiency. The input wavefield of every common offset panel is decomposed into local plane waves at beam centers on the acquisition surface by local slant stacking. Each plane wave contributes a potential single-arrival in Kirchhoff migration. In this way, our method is able to handle multiarrivals caused by model complexity and, therefore, to overcome the limitation of conventional single-arrival Kirchhoff migration. The choice of the width of the beam is critical to the implementation of beam migration. We provide a formula for optimal beam width that achieves both accuracy and efficiency when the velocity model is reasonably smooth. The resulting structural imaging in subsalt and other structurally complex areas is of better quality than that from single-arrival Kirchhoff migration.

scholarly journals Comparing turbulent parameters obtained from LITOS and radiosonde measurements

2014 ◽  
Vol 14 (13) ◽  
pp. 19033-19053 ◽  
Author(s):  
A. Schneider ◽  
M. Gerding ◽  
F.-J. Lübken
Keyword(s):  
Spectral Analysis ◽  
Energy Dissipation ◽  
Dissipation Rate ◽  
Potential Temperature ◽  
Energy Dissipation Rate ◽  
Radiosonde Data ◽  
Turbulence Measurement ◽  
Trace Species ◽  
Ozmidov Scale ◽  
Inner Scale

Abstract. Stratospheric turbulence is important for the mixing of trace species and the energy balance, but direct measurements are sparse due to the required resolution and accuracy. Recently, turbulence parameters such as the energy dissipation rate ε were inferred from standard radiosonde data by means of a Thorpe analysis. To this end, layers with vertically decreasing potential temperature are analysed, which is expected to drive turbulence. Such an application assumes a proportionality between the Thorpe length LT and the Ozmidov scale LO. While this relation is accepted for the ocean, experimental evidence for such proportionality in the stratosphere is sparse. We have developed a high-resolution (8 kHz) turbulence measurement system called LITOS, which for the first time resolves the inner scale of turbulence in the stratosphere. Therewith the energy dissipation rate ε can be determined by spectral analysis. This independent value for ε enables us to check the relation LO ∝ LT. It turns out that no proportionality can be seen in our measurements. Furthermore, dissipation rates obtained from radiosondes deviate up to a factor of ~ 3000 to those obtained by spectral analysis. Some turbulent layers measured by LITOS are not observed by the radiosonde at all, and vice versa.

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