Quantum Key Distribution (QKD) can guarantee security for practical indoor optical wireless environments. The key challenges are to mitigate artificial lighting and ambient light at the receiver. A new spectral region for QKD is proposed and an ideal QKD link model is simulated with experimental ambient light power measurements. Simulation, modelling, and analysis indicates that the carbon dioxide and water absorption band (1370 nm) is a new wavelength region for QKD operation in indoor optical wireless environments. For a feasible QKD link, approximately 20 dB of signal to noise ratio (SNR) is required and a maximum quantum bit error rate (QBER) of 11% when using the BB84 protocol. Links in the new spectral region with a FOV of several degrees are feasible, depending on available components.
Quantum Key Distribution (QKD) can guarantee security for practical indoor optical wireless environments. The key challenges are to mitigate artificial lighting and ambient light at the receiver. A new spectral region for QKD is proposed and an ideal QKD link model is simulated with experimental ambient light power measurements. Simulation, modelling, and analysis indicates that the carbon dioxide and water absorption band (1370 nm) is a new wavelength region for QKD operation in indoor optical wireless environments. For a feasible QKD link, approximately 20 dB of signal to noise ratio (SNR) is required and a maximum quantum bit error rate (QBER) of 11% when using the BB84 protocol. Links in the new spectral region with a FOV of several degrees are feasible, depending on available components.
Quantum Key Distribution (QKD) has the potential to secure indoor optical wireless links. In a typical room scenario, an indoor optical wireless link will have a transmitter on the ceiling and a receiver on a desk. Ambient light from room (typically LED) lighting on the ceiling and sunlight coming through the windows present a challenging environment for free-space QKD links to operate, and a key challenge is to mitigate the noise induced by ambient light, particularly sunlight. A combination of spectral and spatial filtering can be used to reduce the effect of ambient light, with a narrowband optical filter typically used. Moreover, the wavelength of operation is key to further reduce the impact of ambient light. Wavelengths in ‘quiet’ regions of the solar spectrum, such as the atmospheric absorption bands, are promising candidates. We are currently working on a system that operates at 1370 nm, where water and carbon dioxide absorption band in the atmosphere attenuate the solar spectrum substantially. This paper reports the design and modelling of the system, with a series of validation measurements to characterise the effect of solar radiation on a typical photon-counting detector as would be used in a QKD system. The aim of this work is to show the feasibility of the wavelength region around 1370 nm as a necessary step towards a low noise QKD receiver for indoor optical wireless links in a practical environment.
We examine the applicability of wireless indoor quantum key distribution (QKD) in hybrid quantum-classical networks. We propose practical configurations that would enable wireless access to such networks. The proposed scenarios would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. QKD signals, sent through wireless indoor channels, are combined with classical ones and sent over the same fiber link to the remote user. Dense wavelength-division multiplexing would enable the simultaneous transmission of quantum and classical signals over the same fiber. We consider the adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to such an integration. In addition, we consider the loss and the background noise that arise from indoor environments. Decoy-state BB84 and measurement device-independent protocols are employed for the secret key rate analysis.
Among all emerging quantum information technologies, quantum key distribution (QKD) is one of the most developed techniques. QKD harnesses the intrinsic laws of quantum mechanics to provide a method for distributing secret random keys, which can be used for data encryption and decryption between two intended users. QKD has already been demonstrated in different scenarios over optical fibre and in atmospheric channels. QKD has also been used for security assurance in several network settings, in addition of being commercially available today. Despite remarkable progress in QKD systems, convenient access to the developing quantum communications networks is still missing. Adopting QKD in mobile devices would enable such a service, particularly, in indoor environments. This is in line with the recent advancement in fabricating microchip-scale QKD devices, which would ease this incorporation into mobile devices. This work focuses on the access networks, and, in particular, it addresses the wireless mode of access in indoor environments for QKD networks. We find a practical regime of operation, where, in the presence of external light sources and loss, secret keys can be exchanged. We then propose practical configurations that would enable wireless access to hybrid quantum-classical networks. The proposed setups would allow an indoor wireless user, equipped with a QKD-enabled mobile device, to communicate securely with a remote party on the other end of the access network. We account for adverse effects of the background noise induced by Raman scattered light on the QKD receivers due to the transmission of both quantum and classical signals over the same fibre. In addition, we consider the loss and the background noise that arise from indoor environments. We consider a number of discrete and continuous-variable QKD protocols and study their performance in different scenarios. In our analysis we consider the asymptotic scenario, as well as the finite-size key effects. In the former case, an infinite number of signals are assumed to be exchanged between the sender and the recipient, whereas in the latter, which represents the
practical scenario, a finite number of signals are exchanged between the two users. Our results indicate that a feasible regime of operation for wireless QKD exists. This makes the QKD technologies available to end users of a communications network.
The growing role of secure communication in defense networks has increased the need for systems that remain dependable even under advanced cyber-threat conditions. In this work, we study a Quantum Key Distribution (QKD)-enabled Optical Wireless Communication (OWC) link for short-range building-to-building applications. The system is evaluated using a MATLAB-based simulation framework that models a terrestrial free-space optical channel affected by attenuation, beam divergence, pointing misalignment, turbulence-related penalties, and additive noise. Accordingly, the performance of channel impairments is investigated with respect to QBER and the achievable secret key rate using the BB84 protocol. At the same time, a regression model based on ANN is developed to estimate the secret key rate from the measurable channel parameters. Finally, the derived key is used in the example of QOTP encryption to illustrate the secure end-to-end communication. It is concluded from the results that attenuation of channels has the most profound effect on the performance of QKD, particularly under high-loss situations where the key rate significantly decreases. In summary, the results provide a practical baseline for understanding QKD behavior over terrestrial FSO links and point to the need for future experimental verification.
Abstract With increasing demands for secure high-speed wireless communications, integration of quantum key distribution (QKD) into light fidelity (LiFi) systems is a promising method for boosting data confidentiality in optical wireless networks. The BB84 protocol and Mach–Zehnder modulator (MZM) are utilized with a pump-assisted continuous wave laser at 1,550 nm and polarization control components to encode quantum states onto photons. They are transmitted on free space optical (FSO) links with a length ranging from 2 km to 8 km and received using Avalanche photodiodes (APDs) and optical filters. Performance analysis conducted using bit error rate (BER) and Q-factor analysis. BER maintained at zero across all tested configuration and transmission distance up to 8 km indicating excellent signal integrity and security. A highest Q-factor achieved a maximum of 3,055.9, which ensures signal integrity and low interference noise. The system operates at a simulated data rate of 10 Gbps, suitable for high speed optical wireless communication. Consistently high eye height (∼172,210 units) and stable decision thresholds confirm minimal inter-symbol interference and accurate symbol recognition. And the Poincaré sphere showed even polarization stability for different optical power levels. This work presents a simulation-based implementation of a polarization encoded QKD system over a LiFi-enabled FSO communication channel, aiming to enhance secure optical wireless communication. Calculated based on quantum bit error rate (QBER) and included in the theoretical analysis to demonstrate practical secure throughput.