Quantum effects brought to light, and sight

Yakir Aharonov, David Z. Albert, A. Casher +1 more

Cameron Simmons, Yoann Noblet, Alfonso Tello Castillo +1 more

Quantum key distribution (QKD) is a quantum communications protocol which provides the growth of encryption keys under guaranteed security. Due to the single-photon nature of many QKD protocols, QKD systems can be optically jammed by overwhelming a receiver with many photons at wavelengths at which the single photon detectors are responsive, causing a prohibitively high quantum bit error rate (QBER). In satellite QKD (SatQKD), which relies on communication during brief satellite visual contact, short jamming periods could prevent access to secure communications for much longer periods of time. Optical jamming (OJ) can be achieved both from within line-of-sight by targeting the receiver with a light source, or, in the case of downlink SatQKD, from without line-of-sight by reflecting OJ light off the transmitting satellite.1 The latter attack can be effective 1000km from the ground station, which presents challenges to the deployment of SatQKD in mission-critical applications. In this work, we present two investigations for OJ attacks on SatQKD. Firstly, we present an experimental demonstration utilizing SPAD array technology to locate and mitigate within line-of-sight OJ at long range. Secondly, we present simulations quantifying the effectiveness of without line-of-sight OJ against SatQKD systems and outline mitigation techniques inspired by RF communications. Implementation of the mitigation techniques will be essential for defence applications.

Solomon Budnik

WANG Jinyuan, YU Yinchang, LIN Shenghong +5 more

To improve the performance of physical-layer security, secure beamforming schemes were designed for artificial noise (AN)-aided multiple-input single-output visible light communication (VLC) systems. To address the issue that non-line-of-sight (NLoS) channel gains were easily overlooked, a system model that simultaneously considers line-of-sight and NLoS channel gains was established. Under perfect and imperfect channel state information conditions, optimal and robust secure beamforming problems were formulated, respectively. Considering the limitations of semidefinite relaxation (SDR) and Gaussian randomization methods, secure beamforming schemes combining semidefinite programming and penalty function were proposed. Numerical results show that, compared with SDR and Gaussian randomization methods, the proposed schemes can provide at least 3 dB of power gain. Moreover, both the adoption of AN technology and the consideration of NLoS channel gain can effectively reduce the system’s transmission power.

James Kevin Koga

It has been shown that laser sight shown in water can convert some of the light into nonclassical photon pairs. Also, photonic counterparts of Cooper pairs have been shown to occur when light scatters off of various media. Here, we consider the effects of non-classical light produced by such interactions on biological systems and whether there could be an influence.