Quantum Networking

WOMANIUM Global Quantum Media Project Initiative — Winner of Global Quantum Media Project

Introduction

Quantum networking is an emerging field that aims to distribute useful entanglement over long distances, enabling secure and ultra-secure communication, as well as distributed sensing and computation. This article explores the practical aspects of quantum networking, including the design of instrumentation for field deployment, compatibility with existing telecommunication infrastructure, and the integration of quantum sensors and quantum computers. It also discusses the evolution of quantum communications and networking technologies, along with the challenges faced in implementing these systems in the real world. Additionally, it highlights the products and advancements made by Qunnect [1], prominent player in the quantum communications field in the field of quantum networking.

Photo by Christopher Burns on Unsplash

Practical Distribution of Useful Entanglement

The practical distribution of useful entanglement over long distances requires the design of instrumentation that is suitable for field deployment and scalability on existing telecommunication infrastructure. It is essential to ensure that communication qubits are not limited to communication alone but are also compatible with quantum sensors and quantum computers. Furthermore, overcoming fiber transmission losses and topology constraints is crucial to establish efficient and reliable quantum networking systems [2].

Image Credits: https://www.quantum-network.com/

Evolution of Quantum Communications

The evolution of quantum communications and networking has transitioned from digital communications to quantum communications and, eventually, to the concept of a quantum internet. In digital communications, information is carried in pulses of light and mathematically encrypted, providing secure communication. In contrast, quantum communications utilize single light particles to carry information, which is physically encrypted, resulting in ultra-secure communication. The quantum internet takes this a step further, enabling shared information between quantum devices via quantum networks, providing distributed sensing and computation capabilities [2].

How are we creating the quantum internet?

Qunnect’s Quantum Networking Products

Qunnect has developed several products to enable efficient quantum networking. These include:

1. Qu-Memory: The first commercial memory on the market, which does not require external cooling or vacuum support.
2. Qu-Swap: A Bell state measurement station that does not require cryogenic support (currently under development).
3. Qu-Source: The only source on the market that produces entangled photon pairs with a line width of less than 1 GHz at a rate of approximately 10 million pairs per second [3].

Top: A protocol called Hybrid QND-QR is implemented, utilizing nesting level n=1 and segment length L0. The entangled photon pairs are generated by sources on-board the satellite (represented as red stars) and transmitted to ground stations (I). Once the arrival of photons is confirmed by a QND detection, they are transferred to quantum memories (II). Bell State Measurement (BSM) is carried out between the memories to enhance the entanglement between the end stations (III). At the bottom, a novel design is introduced, wherein the QND and quantum memories are also situated on-board an orbiting satellite. Image credits: Fig. 1: Comparison of hybrid and fully space-based quantum repeater architectures. | npj Quantum Information (nature.com)

Other Quantum Internet Companies

Challenges in Quantum Networking

While quantum products and technologies have made significant advancements, several challenges still need to be addressed for the practical implementation of quantum networking systems. These challenges include:

1. Temperature and infrastructure requirements: Quantum systems typically operate at ultra-low temperatures, which necessitate specialized cooling and vacuum infrastructure. However, such requirements are not practical for real-world deployment.
2. Maintenance and stability: Instruments used in quantum networking must be low maintenance and stable to ensure reliable long-term operation.
3. Network losses: Losses incurred during inter-instrument and network transmissions can compound quickly and significantly impact system performance.
4. Environmental perturbations: Real-world telecom fiber is subject to various environmental perturbations, such as temperature fluctuations and physical disturbances, which can degrade the quality of quantum communication signals.
5. Precision and accuracy: Quantum instruments demand highly accurate local references across the network to maintain the precision of measurements and computations [2].

To overcome these challenges, supporting products are necessary to facilitate the deployment of quantum devices across a network. Qunnect offers several support products, including the QU-APC (Auto Polarization Compensator), QU-LOCK (atomic-based reference for telecom and NIR lasers), and QU-SYNC (global timing reference and orchestrator) [4].

Image Credits: Qunnect Debuts QU-APC Instrument with Interactive Demo at the 2023 Optical Fiber Communication Conference and Exhibition (OFC) — Inside Quantum Technology

Entanglement Distribution Networking

Entanglement distribution networking is a fundamental concept in quantum networking. It relies on entanglement swapping, a protocol that allows the distribution of entangled photons over distances beyond the fiber loss limit. In an elementary link, two entanglement sources produce a pair of photons, with each source emitting a different colored photon. One half of the photons is sent to a middling node, while the other half is stored in local quantum memories. At the middling node, the photons are interfered, mapping the entanglement of the remaining photons onto the same state. This process is repeated at other elementary nodes, effectively spreading the entanglement state across the network. By employing entanglement swapping, entanglement distribution networking enables long-distance entanglement between nodes [11].

Image Credits: Quantum Entanglement Conceptual Artwork High-Res Vector Graphic — Getty Images

Next Steps: Entanglement Swapping & Teleportation

To further advance quantum networking, it is crucial to focus on high-quality entangled photon pairs and high pair generation rates to overcome the limitations imposed by the Hz ceiling. Teleportation demonstrations over fiber at any distance utilize time-bin qubits, which are restricted to communication applications. With a high pair generation rate of 10 million pairs per second, the swapping rate can be estimated to be in the kilohertz range. Accounting for fiber loss, these rates would be reduced to approximately 25 Hz. Importantly, these demonstrations employ polarization qubits, which have applications beyond communication purposes [12].

Original Image: Teleportation of quantum entanglement with photons from artificial atoms | Dipartimento di Fisica (uniroma1.it)

Conclusion

Quantum networking holds immense potential for secure communication, distributed sensing, and computation. However, practical implementation requires careful consideration of instrumentation design, compatibility with existing infrastructure, and overcoming various challenges associated with real-world deployment. Qunnect’s quantum networking products, such as Qu-Memory, Qu-Swap, and Qu-Source, contribute to the advancement of this field. By leveraging entanglement swapping and addressing the limitations of current technologies, quantum networking systems can overcome distance constraints and provide a foundation for the future quantum internet.

References

Photo by Sigmund on Unsplash

[1] Qunnect. (n.d.). Enabling the Quantum Internet. [Online]. Available: https://www.qunnect.inc/ [Accessed: July 9, 2023].

[3] Kimble, H. J. (2008). The Quantum Internet. Nature, 453(7198), 1023–1030. https://doi.org/10.1038/nature07127

[4] A. S. Cacciapuoti, M. Caleffi, F. Tafuri, F. S. Cataliotti, S. Gherardini, and G. Bianchi, “Quantum Internet: Networking Challenges in Distributed Quantum Computing,” IEEE Network, vol. 34, no. 1, pp. 137–143, Jan. 2020, doi: 10.1109/mnet.001.1900092.

[2] Qunnect. (n.d.). Quantum Networking Products. Retrieved from https://www.qunnect.com/products/

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[10] WeLinq. (n.d.). Providing links to the future [Online]. Available:
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[11] Y. Wang et al., “Remote entanglement distribution in a quantum network via multinode indistinguishability of photons,” Phys. Rev. A, vol. 106, no. 3, p. 032609, Sep. 2022, doi: 10.1103/PhysRevA.106.032609.

[12] R. B. Jin, M. Takeoka, U. Takagi, et al., “Highly efficient entanglement swapping and teleportation at telecom wavelength,” Sci. Rep., vol. 5, p. 9333, 2015. doi: 10.1038/srep09333.