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Applied Optics

Optimization of FSO quantum backscatter communication

Shlomi Arnon

Published May 14, 2019• 1 citation
Publisher

Abstract

In this paper, the free-space optics (FSO) quantum backscatter communication (QBC), inspired by the quantum illumination concept, is described. In this method, the transmitter generates entangled photon pairs. The signal photon is transmitted in the direction of the modulated retro reflector (MRR) or the tag antenna, and the idler photon is moved to the receiver. The MRR communicates by modulating the received photon and retro-reflecting it back to the receiver. QBC could provide performance improvement in comparison to conventional backscatter communications. In this work, a mathematical model of the FSO QBC systems is derived. In an FSO system, the pointing direction jitter is a stochastic process that reduces the communication performance. In this paper, optimization of FSO QBC performance is proposed to minimize the error probability. This could be done by adapting the telescope gain to jitter a standard deviation amplitude.

DOI
10.1364/ao.58.000f10

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In this paper, the free-space optics (FSO) quantum backscatter communication (QBC), inspired by the quantum illumination concept, is described. In this method, the transmitter generates entangled photon pairs. The signal photon is transmitted in the direction of the modulated retro reflector (MRR) or the tag antenna, and the idler photon is moved to the receiver. The MRR communicates by modulating the received photon and retro-reflecting it back to the receiver. QBC could provide performance improvement in comparison to conventional backscatter communications. In this work, a mathematical model of the FSO QBC systems is derived. In an FSO system, the pointing direction jitter is a stochastic process that reduces the communication performance. In this paper, optimization of FSO QBC performance is proposed to minimize the error probability. This could be done by adapting the telescope gain to jitter a standard deviation amplitude.
In this paper, we propose a novel quantum backscatter communications (QBC) protocol, inspired by the quantum illumination (QI) concept. In the QBC paradigm, the transmitter generates entangled photon pairs. The signal photon is transmitted and the idler photon is kept at the receiver. The tag antenna communicates by performing the pulse amplitude modulation (PAM), binary phase shift keying (BPSK) or quadratic phase shift keying (QPSK) on the signal impinging at the antenna. Using the sum-frequency-generation receiver, our QBC protocol achieves a 6 dB error exponent gain for PAM and BPSK, and 3 dB gain for QPSK over its classical counterpart. Finally, we discuss the QI-enhanced secure backscatter communication.
We present a quantum-correlation-based free-space optical(FSO) link over 250 m using an outdoor active reflector 125 m from the transceiver station. The performance of free-space optical communication can be significantly degraded by atmospheric turbulence effects, such as beam wander and signal fluctuations. We used a 660 nm tracking laser to reduce atmospheric effects, by analyzing the fast beam wander and slow temporal beam drift, using this information to correct the quantum channel alignment of the 810 nm signal photons. In this work, the active reflector consisted of a mirror, a 6-axis hexapod stage, and a long-range wireless bridge. The slow drift of the beam path due to outdoor temperature changes was steered and controlled using wireless optical feedback between the receiver units and the active reflector. Our work provides useful knowledge for improved control of beam paths in outdoor conditions, which can be developed to ensure high quality quantum information transfer in real-world scenarios, such as an unmanned FSO link for urban quantum communication or retro-reflective quantum communication links.
Quantum illumination (QI) is a revolutionary photonic quantum sensing paradigm that enhances the sensitivity of photodetection in noisy and lossy environments. In this paper, we propose to use QI in a quantum backscatter communication (QBC), with the aim of increasing the receiver sensitivity beyond the limits of its classical counterpart. One of the practical challenges in microwave QI is the slow rate at which the entangled microwave modes can be generated. Here, we propose to mitigate this problem by using a multiple-input multiple-output antenna system to synthetically increase the number of efficiently- distinguishable modes in the QBC context.
Multiphoton Quantum Key Distribution (QKD) has recently been proposed to exchange the secret keys using the rotational of polarization over a multi-stage protocol. It has the ability to outperform the weaknesses of a single photon QKD by improving the generation of key rate and distance range. This paper investigates the theoretical aspects of multiphoton QKD protocol’s performance over free space optic (FSO) networks. The most common setup for quantum communication is the single-beam approach. However, the single-beam setup has limitations in terms of high geometrical loss. In this paper, the symmetry multiple-beam for quantum communication which is called as Multiphoton Quantum Communication-Multiple Beam (MQC-MB) is proposed to transmit the multiphoton from the sender to the receiver in order to minimize the impact of geometrical loss that is faced by the single-beam setup. The analysis was carried out through mathematical analysis by establishing the FSO quantum model with the effects of atmospheric and geometrical loss as well as considering atmospheric turbulence modeled by log-normal distribution. The design criteria of FSO, such as the transmitter, receiver, beam divergence, and diameter of apertures, are analytically investigated. The numerical results demonstrate that the MQC-MB outperforms the single-beam in terms of reducing channel loss by about 8 dB and works well under strong turbulence channel. Furthermore, the MQC-MB reduces the quantum bit error rate (QBER) and improves the secret key rate (SKR) as compared to the single-beam system even though the distance between the sender and receiver increases.
Information Reconciliation (IR) in QKD is a fundamental step in ensuring Alice and Bob share identical set of bits (reconciled key). IR could be done by one-way or two-way channel coding using an auxiliary public authenticated channel to send parities to correct the actual labels so that the sample labels at Alice and Bob match. We assume that communication is performed through an Optical Wireless (OW) or Free Space Optics (FSO) channel, which effects the received signal by a stochastic fading due to jitter in pointing. The effect is that the received samples do not match with the transmitted ones, this is the reason why IR is necessary in such a system. In a previous work, we analyzed the system performance over FSO channel, uncovering the dependence between performance and system parameters such as fading variance or the telescope gain. In this paper we want to study the overall performance and try to obtain optimal values for the parameters that influence the sign error probability.
Unmanned aerial vehicles (UAVs)-based free-space optics (FSO)/quantum key distribution (QKD) systems require high-precision pointing mechanisms. This increases system complexity and limits rapid deployment for lightweight and energy-constrained UAVs. This paper proposes a modulating retroreflector (MRR)-equipped UAV architecture for BB84-QKD systems that enables simplified yet accurate tracking while relaxing pointing requirements. A realistic quantum channel model is developed, for which we newly derive the channel probability distribution of transmittance (PDT). Capitalizing on the derived channel PDT, several QKD performance metrics are analytically obtained. Numerical results verify the feasibility of the proposed MRR-aided UAV for practical QKD deployment, highlight its effectiveness over conventional UAV-ground systems, and validate the accuracy of the developed analytical framework.