Experimental investigation of quantum key distribution over a water channel

Abstract

Quantum key distribution (QKD) has undergone significant development in recent decades, particularly with respect to free-space (air) and optical fiber channels. Here, we report the first proof-ofprinciple experiment for the BB84 protocol QKD over a water channel. Firstly, we demonstrate again the polarization preservation properties of the water channel in optical transmission according to the measured Mueller matrix, which is close to the unit matrix. The reason for the polarization preservation, revealed by Monte Carlo simulation, is that almost all the received photons are unscattered.Then, we performed the first polarization encoding BB84 protocol QKD over a 2.37m water channel. The results show that QKD can be performed with a low quantum bit error rate (QBER), less than 3.5%, with different attenuation coefficients.

Entanglement transmission through dense scattering medium

“…However, the scattering effects are not treated thoroughly in these theoretical models, since in some scenarios the inconspicuous influences of scattered effects on light transmissions are neglected. While for the underwater links, the studies mainly focus on the classical effects of the water on propagating optical signals [21][22][23][24], the related experimental demonstration of the feasibility of entanglement transmission [25], the performance analysis and related experimental demonstrations of quantum key distribution [26][27][28][29][30] and quantum state transmission [26,31,32]. The knowledges of the influences of nontrivial scattering effects on the nonclassical properties, especially the entanglement, for atmospheric and underwater environments are almost blank.…”

Performance analysis of quantum key distribution in underwater turbulence channels

“…The current literature on QKD is mainly limited to the transmissions over fiber optic, atmospheric or satellite links and are not directly applicable to underwater environments with different channel characteristics. There have been only some recent efforts on underwater QKD [16][17][18][19][20][21][22][23][24][25]. For example, in [16] and [17], based on the well-known Beer-Lambert path loss model, the maximum secure communication distance for BB84 protocol in underwater environments was derived to achieve a desired level of quantum bit error rate (QBER) and the secret key rate (SKR).…”

“…Using these simulated underwater channels, the QBER performance of BB84 QKD protocol was computed. Some experimental demonstrations of underwater QKD were further reported in [20][21][22] using aquariums and water tanks. Specifically, in [20] The above theoretical and experimental works consider only the path loss, but ignore the effects of turbulence.…”

Characterization of an underwater channel for quantum communications in the Ottawa River

“…Underwater quantum communications have been numerically investigated [23] and experimentally demonstrated in laboratory conditions using polarization [24,25], in outdoor conditions using the OAM degree of freedom [26], and over a 55 m water channel using polarization [27] modes [28]. These experimental investigations have lead to several numerical investigations of QKD in underwater channels [29][30][31].…”