In this research work, a simulator with time-domain visualizers and configurable parameters using a continuous time simulation approach with Matlab R2019a is presented for modeling and investigating the performance of optical fiber and free-space quantum channels as a part of a generic quantum key distribution system simulator. The modeled optical fiber quantum channel is characterized with a maximum allowable distance of 150 km with 0.2 dB/km at =1550nm. While, at =900nm and =830nm the attenuation values are 2 dB/km and 3 dB/km respectively. The modeled free space quantum channel is characterized at 0.1 dB/km at =860 nm with maximum allowable distance of 150 km also. The simulator was investigated in terms of the execution of the BB84 protocol based on polarizing encoding with consideration of the optical fiber and free-space quantum channel imperfections and losses by estimating the quantum bit error rate and final secure key. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result that emerged from the simulated data generated and detected is that the modeling process provides guidance for optical quantum channels design and characterization for other quantum key distribution protocols.
In this research work, a simulator with time-domain visualizers and configurable parameters using a continuous time simulation approach with Matlab R2019a is presented for modeling and investigating the performance of optical fiber and free-space quantum channels as a part of a generic quantum key distribution system simulator. The modeled optical fiber quantum channel is characterized with a maximum allowable distance of 150 km with 0.2 dB/km at =1550nm. While, at =900nm and =830nm the attenuation values are 2 dB/km and 3 dB/km respectively. The modeled free space quantum channel is characterized at 0.1 dB/km at =860 nm with maximum allowable distance of 150 km also. The simulator was investigated in terms of the execution of the BB84 protocol based on polarizing encoding with consideration of the optical fiber and free-space quantum channel imperfections and losses by estimating the quantum bit error rate and final secure key. This work shows a general repeatable modeling process for significant performance evaluation. The most remarkable result that emerged from the simulated data generated and detected is that the modeling process provides guidance for optical quantum channels design and characterization for other quantum key distribution protocols.
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.
Quantum Key Distribution (QKD) is a potential defense against future quantum attacks that can break traditional encryption algorithms, such as RSA and ECC. The current work is based on the development of the BB84 protocol with the features of utilizing quantum mechanics and eavesdropping detection through signal disturbance. A simulation of the BB84 protocol was built using polarization encoding over a 10 km single-mode optical fiber using OptiSystem software. The system consists of standard telecom equipment, such as a continuous wave laser at a frequency of 193.1 THz, polarization controllers, and single-photon detectors. Both secure and insecure cases were simulated, where an attacker (Eve) had used an intercept-resend attack. The outcome showed significant Bit Error Rate (BER) and Quantum Bit Error Rate (QBER) increases during attacks, thus proving the protocol's vulnerability to interference. In addition, a special intrusion detection system based on BER was used to identify such anomalies in real-time. The simulation illustrates the feasibility of using QKD in today's optical networks to secure communications.
Abstract Quantum key distribution (QKD) is a process that utilizes the principles of quantum mechanics to securely share a secret key between two parties, ensuring unconditional security. Diverse QKD protocols are established to guarantee the security and integrity of information against any attempts by an eavesdropper monitoring the transferred photons. One of these protocols is the six-state protocol. This work employs OptiSystem 21.1 simulation software to design and emulate the six-state protocol, wherein polarization states are produced through random switching control rather than optical modulators. The protocol’s performance, indicated by quantum bit error rate and secure key rate, is analytically examined for both free space optical (FSO) channel and optical fiber channel, incorporating parameters from two types of commercial single-photon detectors to enhance realism. The maximum secure key rate attains 5.439 Mbps at 10 km of optical fiber, in contrast to 1.674 Mbps at 0.2 km under clear weather conditions in the FSO quantum channel utilizing ID 281 single-photon detector modules across both channels. The maximum distance that guarantees secure key rate with ID 281 for FSO channel is 2 km with 1760 bps with heavy haze compared to 100 km optical fiber with secure key rate of 15,000 bps.
Abstract As quantum computing continues to demonstrate its potential to break through existing cryptographic systems, quantum key distribution (QKD) provides a novel approach to protect communications in the post-quantum era, but presents complex challenges in terms of research and widespread adoption. Although the resource-intensive nature of QKD setups limits experimental studies to specialized laboratories, we present an end-to-end simulation that models photon generation, transmission, and detection, thereby lowering the barrier to testing hypotheses regarding experimental setups under realistic conditions. In this study, a fiber optic-based simulation was utilized along with a quantum circuit and a detailed noise model within the BB84 protocol to recreate an experimental setup. Our BB84 simulation retained ≈50% of transmitted bits after sifting, matching the experimental expectations, and produced quantum bit error rate (QBER) values that rose with increasing channel length. Our model incorporates customizable noise, such as multi-photon emissions and channel disturbances, directly into the key exchange process, yielding QBER values of ≈4.5% at 20 km and ≈11% at 120 km, consistent with physical systems under the same conditions. Our findings support the development of QKD as a scalable solution for securing the quantum internet and future communication networks.
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.
A complete fiber-based polarization encoding quantum key distribution (QKD) system based on the BB84 protocol has been developed at National Institute of Standard and Technology (NIST). The system can be operated at a sifted key rate of more than 4 Mbit/s over optical fiber of length 1 km and mean photon number 0.1. The quantum channel uses 850 nm photons from attenuated high speed VCSELs and the classical channel uses 1550 nm light from normal commercial coarse wavelength division multiplexing devices. Sifted-key rates and quantum error rates at different transmission rates are measured as a function of distance (fiber length). A polarization auto-compensation module has been developed and utilized to recover the polarization state and to compensate for temporal drift. An automatic timing alignment device has also been developed to quickly handle the initial configuration of quantum channels so that detection events fall into the correct timing window. These automated functions make the system more practical for integration into existing optical local area networks.