Strong enhancing effect of correlations of photon trajectories on laser beam scintillations

The establishment of quantum communication links over a global scale is enabled by satellite nodes. We examine the influence of Earth's atmosphere on the performance of quantum optical communication channels with emphasis on the downlink scenario. We derive the geometrical path length between a moving low Earth orbit satellite and an optical ground station as a function of the ground observer's zenith angle, his geographical latitude, and the meridian inclination angle of the satellite. We show that the signal distortions due to regular atmospheric refraction, atmospheric absorption, and turbulence have a strong dependence on the zenith angle. The observed saturation of transmittance fluctuations for large zenith angles is explained. The probability distribution of the transmittance for slant propagation paths is derived, which enables us to perform the security analysis of decoy state protocols implemented via satellite-mediated links.

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“…(56). Finally, we note that the parameters (60) and (63) still contain the beam wandering variance, and we calculate σ 2 BW by means of Eq. (52).…”

Section: Probability Distribution Of Transmittancementioning

confidence: 99%

Satellite-mediated quantum atmospheric links

2019

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“…The evolution equation for PDF is derived from Heisenberg's equation. Although in more general case its evolution is gathered by Boltzmann-Langevin equation [29] which takes to account whole range of possible changes in photon momentum due to collisions with atmosphere inhomogeneities, for reasonably long distances (see [30]) description with collisionless Boltzmann equation…”

Section: Photon Distribution Functionmentioning

confidence: 99%

“…where g = |g| and we also used Markov approximation index-of-refraction spectrum is delta-correlated in the direction of propagation, which was rigorously justified in [30]. After integration over direction of g…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…First two terms in square brackets represent correlation of waves with same pairs {r, q} and {r , q }. The terms that include Bessel functions consider cross-correlation of photon trajectories ({r, q} and {r , q } are different) which were extensively reviewed in [30]. In (A7) and (A8) we omit the dependence on angle between ∆r and g (see Eq.…”

Section: Acknowledgmentsmentioning

confidence: 99%

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Fourth-order moment of the light field in atmosphere

Baskov¹,

Chumak²

2020

J. Opt.

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Collisionless Boltzmann equation is used to describe the intensity correlations in partially saturated and fully saturated regimes in terms of photon distribution function in the phase space. Explicit expression for fourth moment of the light fields is obtained for the case of moderate and strong turbulence. Such expression consists of two terms accounting for two regions in the phase space that independently contribute to the correlation function. It is shown that present solution agrees with previous results for fully saturated regime. Additionally it embodies the effect of partially saturated radiation where the correlations of photon trajectories are important and the magnitude of the scintillation index is well above the unity. Fourth moment is used to study the fluctuations of transmittance which consider the effect of finite detector aperture.

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“…Here k is the optical wave number, C 2 n is the turbulence refractive-index structure constant, L is the propagation length, W 0 is the beam-spot width at the transmitter site, and Ω=kW 2 0 /2L is the Fresnel parameter. In general, the calculation of the correlation functions and their moments requires high-accuracy numerical integrations [42,62,63].…”

Section: Application To Atmospheric Channelsmentioning

confidence: 99%

Theory of atmospheric quantum channels based on the law of total probability

2018

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The atmospheric turbulence is the main factor that influences quantum properties of propagating optical signals and may sufficiently degrade the performance of quantum communication protocols. The probability distribution of transmittance (PDT) for free-space channels is the main characteristics of the atmospheric links. Applying the law of total probability, we derive the PDT by separating the contributions from turbulence-induced beam wandering and beam-spot distortions. As a result, the obtained PDT varies from log-negative Weibull to truncated log-normal distributions depending on the channel characteristics. Moreover, we show that the method allows one to consistently describe beam tracking, a procedure which is typically used in practical long-distance free-space quantum communication. We analyze the security of decoy-state quantum key exchange through the turbulent atmosphere and show that beam tracking does not always improves quantum communication.

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Strong enhancing effect of correlations of photon trajectories on laser beam scintillations

Cited by 15 publications

References 36 publications

Satellite-mediated quantum atmospheric links

Satellite-mediated quantum atmospheric links

Fourth-order moment of the light field in atmosphere

Theory of atmospheric quantum channels based on the law of total probability

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