Simultaneous Classical and Quantum Communications Enable Integration, Addressing Challenges for Next-Generation Networks

The increasing sophistication of cyber threats demands innovative approaches to network security, and researchers are now investigating the potential of integrating quantum communications with existing classical infrastructure. Phuc V. Trinh from The University of Tokyo, alongside Shinya Sugiura and Carlo Ottaviani, lead a team that explores protocols enabling simultaneous classical and quantum data transmission using a single set of transceivers, significantly reducing the costs and complexities associated with deploying separate systems. This work, also involving Chao Xu and Lajos Hanzo from the University of Southampton, demonstrates a pathway towards more secure and efficient communication networks, extending beyond traditional optical frequencies into the terahertz spectrum and potentially even to millimeter-wave and microwave frequencies. By identifying key challenges to practical implementation, the team paves the way for a future where quantum-enhanced security becomes a readily available feature of everyday communication. Neural networks create opportunities for integrating quantum communications into existing classical infrastructure, but substantial challenges remain, including high costs, compatibility issues, and the need for extra hardware. To address these hurdles, researchers explore novel protocols that enable simultaneous classical and quantum communications, relying on a single set of transceivers to jointly modulate and decode information onto the same signal. This work emphasizes extending quantum communication capabilities beyond traditional optical bands into the terahertz, and potentially even to millimetre wave frequencies, aiming to reduce infrastructure costs, simplify deployment, and expand the bandwidth available for quantum communication systems. Simultaneous Classical and Quantum Communication System Researchers developed a novel approach to integrate classical and quantum communications, enabling simultaneous transmission over the same signal and utilizing a single set of transceivers. This system overcomes the limitations of existing quantum communication methods, which typically require dedicated hardware and separate channels, increasing costs and energy consumption. The study pioneers a technique called simultaneous classical and quantum communication (SCQC), where both types of information are jointly modulated and decoded onto the same carrier wave. This tightly integrated infrastructure improves hardware reuse and energy efficiency, making it suitable for deployment in resource-constrained platforms like satellites and unmanned aerial vehicles. The core of this work involves engineering a system capable of overcoming signal overlap that introduces noise and potentially degrades both classical and quantum performance. Scientists meticulously designed protocols to jointly modulate classical and quantum information, transmitting it over a shared physical channel. This approach contrasts with coexistent classical and quantum communication schemes, which allocate distinct time slots, frequency bands, or wavelengths, still requiring separate transceiver hardware and reducing spectral efficiency.

The team focused on SCQC to minimize implementation costs and maximize resource utilization, particularly in scenarios demanding modest infrastructure modifications. To assess the performance of SCQC, researchers conducted detailed comparisons with coexistent schemes, evaluating indicators such as hardware requirements, spectral efficiency, interference effects, data and key rates, and technological maturity. The study highlights the potential of SCQC to extend quantum communication beyond traditional optical bands, exploring terahertz, millimeter-wave, and microwave frequencies. This expansion broadens the scope of applications, including secure low-latency communication for robotic surgery, short-range links between base stations and mobile devices, and inter-satellite communication in low Earth orbit. While acknowledging the challenges of thermal noise and path loss at higher frequencies, the team demonstrates the feasibility of leveraging these bands for limited-range SCQC, bridging the gap between optical and microwave technologies. The research envisions a multi-band wireless infrastructure empowered by SCQC, supporting diverse applications across various frequency bands and communication ranges. Simultaneous Classical and Quantum Communication Demonstrated This research explores Simultaneous Classical and Quantum Communication (SCQC) as a promising solution for integrating quantum security into future wireless networks, particularly Satellite-Airborne-Ground Integrated Networks (SAGINs). SCQC allows the transmission of both classical and quantum information over the same physical channel, reducing hardware complexity, cost, and energy consumption compared to separate systems. Key benefits include reduced hardware requirements, lower deployment and operational costs, and suitability for resource-constrained platforms. The paper leans towards Continuous Variable QKD (CV-QKD) as a viable option for SCQC due to its compatibility with existing classical communication infrastructure, utilizing Frequency Division Multiplexing (FDM) to separate classical and quantum signals and leveraging existing optical fiber and wireless links. SCQC holds significant potential for enhancing the security of future wireless networks, and ongoing research and technological advancements are paving the way for practical implementation, particularly in the context of SAGINs. The paper emphasizes the need for continued research in areas like hardware development, propagation modeling, and protocol adaptation to overcome these challenges and realize the full benefits of SCQC. Terahertz SCQC for Wireless Quantum Security This research demonstrates a compelling solution for embedding quantum security into next-generation wireless networks through a technique called simultaneous classical and quantum communication (SCQC). By enabling the transmission of both classical and quantum signals using a shared system, the team significantly reduces the hardware requirements, deployment costs, and energy consumption associated with secure communication networks, particularly for resource-constrained platforms. This approach offers a pathway towards more practical and efficient quantum-secured networks.

The team successfully explored extending SCQC beyond traditional optical frequencies into the terahertz, millimeter-wave, and microwave bands, broadening the potential applications of this technology. While optical frequencies currently offer the most mature domain for SCQC, extending these concepts to other bands is essential for realizing multi-band networks. However, realizing SCQC in these higher frequency bands presents significant challenges, including thermal noise, atmospheric attenuation, and limitations in current hardware and propagation modeling. Future research must address these limitations to advance secure, unified quantum-classical communication across the full spectrum.

The team identifies the need for breakthroughs in materials science, such as silicon photonics, and the development of compact, high-speed quantum-capable electronics to fully realize the potential of SCQC in the terahertz band. Continued investigation into propagation modeling and protocol adaptation will also be crucial for overcoming the challenges associated with higher frequency bands. 👉 More information 🗞 Simultaneous Classical and Quantum Communications: Recent Progress and Three Challenges 🧠 ArXiv: https://arxiv.org/abs/2512.10176 Tags: