Entanglement-based wavelength multiplexed quantum communication network (1801.06194v1)

Abstract: Quantum networks scale the advantages of quantum communication protocols to more than just two distant users. Here we present a fully connected quantum network architecture in which a single entangled photon source distributes quantum states to a multitude of users. Our network architecture thus minimizes the resources required of each user without sacrificing security or functionality. As no adaptations of the source are required to add users, the network can readily be scaled to a large number of clients, whereby no trust in the provider of the quantum source is required. Unlike previous attempts at multi-user networks, which have been based on active components, and thus limited to some duty cycle, our implementation is fully passive and thus provides the potential for unprecedented quantum communication speeds. We experimentally demonstrate the feasibility of our approach using a single source of bi-partite polarization entanglement which is multiplexed into 12 wavelength channels to distribute 6 states between 4 users in a fully connected graph using only 1 fiber and polarization analysis module per user.

• The paper demonstrates a scalable architecture by using a single entangled photon source to distribute quantum states via 12 wavelength channels without active switching.
• Experimental validation with four users over single-mode fibers confirmed high fidelity of entangled states and robust secure key distribution.
• The approach enhances network scalability and commercial viability by enabling passive, fully connected quantum communication infrastructures.

Entanglement-Based Wavelength Multiplexed Quantum Communication Network

The paper presents a novel approach to quantum communication networks leveraging entanglement-based wavelength multiplexing to significantly enhance scalability and efficiency. The primary innovation here is the utilization of a single entangled photon source to distribute quantum states across multiple users, forming a fully connected network without relying on active switching components. This methodology promises higher communication rates by eliminating output restrictions typically imposed by hardware switches, positioning it as an optimal candidate for large-scale quantum network applications.

Key Contributions

The design centers around a few core principles aimed at maximizing the practicality and robustness of quantum networks:

1. Single Source Architecture: The network operates with one entangled photon source, simplifying the resource requirements per user. This architecture supports the simultaneous entanglement distribution to all pairs of users.
2. Wavelength Division Multiplexing (WDM): The paper employs WDM to multiplex 12 wavelength channels to distribute bi-partite entangled states between any two users in a fully connected network. This is particularly advantageous as it streamlines scalability, allowing additional users to be incorporated without reconfiguring the central photon source.
3. Passive Implementation: Eschewing traditional active routing, the design maintains high-speed data transfer capabilities and operational longevity.

Experimental Validation

The proposed network structure was experimentally demonstrated by connecting four users through single-mode fibers, each equipped to handle a polarized entangled photon pair using WDM. This setup facilitated the generation of secure quantum keys across each pairwise user connection. Key experimental results include:

• Six polarization entangled states were distributed among four users across 12 wavelength channels.
• Photon detection and data analysis modules confirmed the high fidelity of the shared entangled states, indicating strong implementation feasibility.

Theoretical and Practical Implications

The network's design and successful validation bear several implications for the future of quantum communication:

• Scalability: The ability to add users without additional source reconfiguration or network downtime presents a significant scalability advantage. Furthermore, the design is adaptable to more complex network topologies beyond fully connected networks.
• Security: By eliminating the need for trusted nodes and using purely entangled states, the architecture inherently supports secure quantum communication.
• Commercial Viability: With ongoing advances in detector performances and multiplexing technology, such networks can be seamlessly integrated into existing telecommunication infrastructures and reflect promising prospects for commercial deployment.

Future Directions

The potential next steps stem primarily from extending this network architecture to larger scales and diversifying its applications:

• Exploring the integration with time division multiplexing (TDM) to enhance resource allocation and management.
• Investigating the network's adaptability to form more complex organizational structures like star or mesh topologies.
• The introduction of commercially viable, user-configurable networks using quantum mechanics to accommodate real-world communication needs efficiently.
• Enhancing the source brightness and detector quality would further elevate the rate and distance capabilities of the entanglement distribution.

This paper exemplifies a critical step forward in the development of robust, efficient, and scalable quantum networks. It sets the foundation for future practical implementations, making it a significant reference point for ongoing research in quantum networking and communication. The demonstrated ability to support flexible, high-speed communication between multiple parties offers a glimpse into the promising future of quantum communications.