Influence of atmospheric turbulence on the propagation of quantum states of light using plane-wave encoding

Abstract

Abstract:We consider the possibility of performing quantum key distribution (QKD) by encoding information onto individual photons using plane-wave basis states. We compare the results of this calculation to those obtained by earlier workers, who considered encoding using OAM-carrying vortex modes of the field. We find theoretically that plane-wave encoding is less strongly influenced by atmospheric turbulence than is OAM encoding, with potentially important implications for free-space quantum key distribution.

Security of high-dimensional quantum key distribution protocols using Franson interferometers

“…If we are to increase the amount of information encoded on each photon, we must use high-dimensional entanglement. For example, one can use the orbital angular momentum of photons to encode multiple bits per photon [18,[29][30][31], though one is then susceptible to the deleterious effects of atmospheric turbulence in many applications [32]. An alternative is to use photons that are entangled in their time of arrival, which is often called energy-time entanglement.…”

Demonstration of a 280 Gbit/s free-space space-division-multiplexing communications link utilizing plane-wave spatial multiplexing

“…A second lens placed at the receiver separates these tilted plane-waves in spatial location at its back focal plane with relatively low crosstalk (see Fig.1) [12]. We note that plane-waves in the context of a communications link have been postulated to offer comparable channel capacity to other orthogonal mode sets [12], along with being shown to potentially be more resilient to crosstalk induced by atmospheric turbulence than LG modes [14,15]. Our approach is similar to line-of-sight (LOS) MIMO implemented in RF wireless communications, where an array of spatially separated transmitters and receivers are used.…”

“…For the case of planewaves, the ability to resolve the different plane-wave channels is connected with the diffraction limit of the optical system [12,14]. A tilted plane-wave can described in the z-y plane as,…”

“…This linear shift is directly related to the angular tilt, α, with respect to the system's axis, which is defined by the center of the spherical lens the angular tilt between any two channels [12,14]. For a given aperture size L, there is a minimum requirement that α = 2π/L for the planewave states to be orthogonal [14]. Therefore, plane-waves with tilt angles larger than this minimum value of α, could potentially be separated in the far-field with relatively low crosstalk (see Fig.…”

Comparing the information capacity of Laguerre–Gaussian and Hermite–Gaussian modal sets in a finite-aperture system

“…From a technological perspective some spatial modes are easier to generate or detect than others: certain spatial modes might correspond to the eigenmodes of a particular transmission system, and hence exhibit reduced cross talk, or be robust to specific aberrations [20] or symmetry shifts [21]. But in general, for a fixed Fresnel number, and therefore a limiting channel capacity, there is superficially no reason to favour one modal set over another.…”