Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Optics Express

Amplified entanglement-assisted communication systems operated in a desert environment and strong atmospheric turbulence regime

Vijay Nafria, Ivan B. Djordjević

Published Nov 28, 2024• 7 citations
Publisher

Abstract

In this paper, we are presenting results that go against the common belief that entanglement is destroyed by the amplification using an EDFA. Here we demonstrate the quantum advantage of entanglement-assisted communication at 10Gb/s, employing LDPC-coded BPSK, over classical laser communication even after the amplification of signal photons is performed by the EDFA in order to improve the reliability of entanglement-assisted (EA) communication operating in turbulent 1.5 km terrestrial FSO channels. To make the EA system more robust against various atmospheric effects such as scattering, absorption, and turbulence effects we perform the optical phase-conjugation on idler photons rather than turbulence-affected signal photons and use adaptive optics to make additional improvements in terms of the bit-error rate.

DOI
10.1364/oe.543021

Related papers

Amplified Entanglement Assisted Communication Outperforming Classical Laser Communication in Strong Atmospheric Turbulence Regime

Vijay Nafria, Ivan B. Djordjević

Contrary to the common belief that EDFA can destroy the entanglement, we demonstrate experimentally that in entanglement assisted communication systems dominated by attenuation effects rather than noise, the signal photons can be amplified by the EDFA without destroying the entanglement. We perform experiments over terrestrial free-space optical testbed developed at the University of Arizona, composed of the FSO link that is 1.5 km in length. We demonstrate that the amplified entanglement assisted communication system at $10 \mathrm{~Gb} / \mathrm{s}$, operated in strong turbulence regime, significantly outperforms the corresponding classical communication system operated in medium turbulence regime, clearly representing the quantum advantage. To reduce the system cost, the entanglement generation source is implemented by employing only the telecom C-band based devices.

International Conference on Transparent Optical Networks•Jul 14, 2024•0 citations

Entanglement assisted communication over the free-space optical link with azimuthal phase correction for atmospheric turbulence by adaptive optics

Vijay Nafria, Ivan B. Djordjević

To improve the reliability of entanglement-assisted (EA) communication over turbulent FSO channels we propose to perform the optical phase-conjugation on idler photons rather than turbulence affected signal photons and use adaptive optics. We experimentally demonstrate that reliable EA communication over outdoor 1.45 km FSO link, established at University of Arizona campus, is possible in strong turbulence regime.

Optics Express•Oct 30, 2023•26 citations

Entanglement Assisted Communication over Turbulent Free-Space Optical (FSO) Link with Phase Conjugation on Idler Photons and Adaptive Optics

Vijay Nafria, Ivan B. Djordjević

To improve the reliability of entanglement-assisted (EA) communication over turbulent FSO channels we propose to perform the phase conjugation on idler photons instead of turbulence affected signal photons and use adaptive optics. We experimentally demonstrate that reliable EA communication over outdoor 1.45km FSO link, established at University of Arizona, is possible.

OSA Advanced Photonics Congress•Jan 1, 2023•2 citations

Entanglement Assisted Communications with Phase-Conjugation on Idler Photons Outperforming Entanglement Assisted Systems with Phase-Conjugated Receivers

Ivan B. Djordjević

Optical communications over terrestrial free-space optical (FSO) channels are affected by various effects including diffraction, absorption, scattering, and turbulence effects. In several recent papers we have shown that entanglement assisted (EA) communication systems significantly outperform corresponding classical counterparts in strong turbulence regime. In traditional EA communications the phase-conjugation, required before the homodyne detection takes place, is performed on signal photons. However, given that many photons get lost due to diffraction, scattering, absorption, and turbulence effects, it is extremely difficult to perform the phase-conjugation on received signal photons when average number of received photons is smaller than 1. To solve this problem, we recently have proposed to perform phase-conjugation on bright idler photons instead. To operate the EA communication system over turbulent FSO links it is required to generate many bright entangled photons so that signal photons can survive beyond strong turbulence regime. To solve this problem, we have proposed to properly design periodically poled lithium niobate waveguides so that we can use telecom available lasers operated in S-, C-, and L-bands as the pump lasers instead of high-cost 780 nm pump lasers. In this invited paper, we will review our recent activities in EA communion studies over terrestrial FSO links and present recent experimental results demonstrating that EA communication systems performing the phase-conjugation on idler photons significantly outperforms both classical counterpart and the EA communications with phase-conjugated receiver in strong turbulence regime.

International Conference on Transparent Optical Networks•Jul 6, 2025•0 citations

Entanglement assisted free-space optical communication with two-pump-based entanglement generation outperforming classical laser communication in strong turbulence regime at 10 Gb/s

Vijay Nafria, Ivan B. Djordjević

A high-speed entanglement assisted communication that operates at 10 Gb/s is proposed, which performs a highly efficient, PPLN-waveguide-based, entanglement generation by making the simultaneous use of S- and L-band pumps. The two-pump-based entanglement generation source satisfies the quasi-phase-matching-condition over the entire C-band. To improve the system reliability, our system performs the phase-conjugation on idler photons in contrast to conventional ways of performing the phase-conjugation on signal photons. To study the performance of the proposed entanglement-assisted system we have developed the 1.5 km long outdoor free-space optical (FSO) link at the University of Arizona campus. Experimental results indicate that the proposed entanglement-assisted system significantly outperforms the classical counterpart at 10 Gb/s, operated in strong turbulence regime. We also demonstrate that the traditional entanglement-assisted system performing the optical phase conjugation on signal photons at the receiver side is not operational at all in strong turbulence regime given that it is extremely difficult to perform the phase-conjugation on weak signal photons when the number of received photons is low. To improve the system performance the adaptive optics is performed on signal photons.

Optics Express•Dec 4, 2024•7 citations

10Gb/s Entanglement Assisted Communication over Free-Space Optical Link with Phase Conjugation on Idler Photons and Improvements from Adaptive Optics

Vijay Nafria, Ivan B. Djordjević

We demonstrate record 10 Gb/s entanglement assisted communication over 1.5 km long turbulent free-space optical link in which optical phase-conjugation is performed on bright idler photons. To further improve the system performance adaptive optics is used.

•Jan 1, 2024•2 citations
In this paper, we are presenting results that go against the common belief that entanglement is destroyed by the amplification using an EDFA. Here we demonstrate the quantum advantage of entanglement-assisted communication at 10Gb/s, employing LDPC-coded BPSK, over classical laser communication even after the amplification of signal photons is performed by the EDFA in order to improve the reliability of entanglement-assisted (EA) communication operating in turbulent 1.5 km terrestrial FSO channels. To make the EA system more robust against various atmospheric effects such as scattering, absorption, and turbulence effects we perform the optical phase-conjugation on idler photons rather than turbulence-affected signal photons and use adaptive optics to make additional improvements in terms of the bit-error rate.
Contrary to the common belief that EDFA can destroy the entanglement, we demonstrate experimentally that in entanglement assisted communication systems dominated by attenuation effects rather than noise, the signal photons can be amplified by the EDFA without destroying the entanglement. We perform experiments over terrestrial free-space optical testbed developed at the University of Arizona, composed of the FSO link that is 1.5 km in length. We demonstrate that the amplified entanglement assisted communication system at 10 Gb/s10 \mathrm{~Gb} / \mathrm{s}10 Gb/s, operated in strong turbulence regime, significantly outperforms the corresponding classical communication system operated in medium turbulence regime, clearly representing the quantum advantage. To reduce the system cost, the entanglement generation source is implemented by employing only the telecom C-band based devices.
Optical communications over terrestrial free-space optical (FSO) channels are affected by various effects including diffraction, absorption, scattering, and turbulence effects. In several recent papers we have shown that entanglement assisted (EA) communication systems significantly outperform corresponding classical counterparts in strong turbulence regime. In traditional EA communications the phase-conjugation, required before the homodyne detection takes place, is performed on signal photons. However, given that many photons get lost due to diffraction, scattering, absorption, and turbulence effects, it is extremely difficult to perform the phase-conjugation on received signal photons when average number of received photons is smaller than 1. To solve this problem, we recently have proposed to perform phase-conjugation on bright idler photons instead. To operate the EA communication system over turbulent FSO links it is required to generate many bright entangled photons so that signal photons can survive beyond strong turbulence regime. To solve this problem, we have proposed to properly design periodically poled lithium niobate waveguides so that we can use telecom available lasers operated in S-, C-, and L-bands as the pump lasers instead of high-cost 780 nm pump lasers. In this invited paper, we will review our recent activities in EA communion studies over terrestrial FSO links and present recent experimental results demonstrating that EA communication systems performing the phase-conjugation on idler photons significantly outperforms both classical counterpart and the EA communications with phase-conjugated receiver in strong turbulence regime.
A high-speed entanglement assisted communication that operates at 10 Gb/s is proposed, which performs a highly efficient, PPLN-waveguide-based, entanglement generation by making the simultaneous use of S- and L-band pumps. The two-pump-based entanglement generation source satisfies the quasi-phase-matching-condition over the entire C-band. To improve the system reliability, our system performs the phase-conjugation on idler photons in contrast to conventional ways of performing the phase-conjugation on signal photons. To study the performance of the proposed entanglement-assisted system we have developed the 1.5 km long outdoor free-space optical (FSO) link at the University of Arizona campus. Experimental results indicate that the proposed entanglement-assisted system significantly outperforms the classical counterpart at 10 Gb/s, operated in strong turbulence regime. We also demonstrate that the traditional entanglement-assisted system performing the optical phase conjugation on signal photons at the receiver side is not operational at all in strong turbulence regime given that it is extremely difficult to perform the phase-conjugation on weak signal photons when the number of received photons is low. To improve the system performance the adaptive optics is performed on signal photons.