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arXiv:2505.19270 · Quantum Computing, Communication, and Simulation

Effect of noise and topologies on multi-photon quantum protocols

Nitin Jha, Abhishek Parakh, Mahadevan Subramaniam

Published Mar 12, 2024• 2 citations
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Abstract

Quantum-augmented networks aim to use quantum phenomena to improve detection and protection against malicious actors in a classical communication network. This may include multiplexing quantum signals into classical fiber optical channels and incorporating purely quantum links alongside classical links in the network. In such hybrid networks, quantum protocols based on single photons become a bottleneck for transmission distances and data speeds, thereby reducing entire network performance. Furthermore, many of the security assumptions of the single-photon protocols do not hold up in practice because of the impossibility of manufacturing single-photon emitters. Multi-photon quantum protocols, on the other hand, are designed to operate under practical assumptions and do not require single photon emitters. As a result, they provide higher levels of security guarantees and longer transmission distances. However, the effect of channel and device noise on multiphoton protocols in terms of security, transmission distances, and bit rates has not been investigated. In this paper, we focus on channel noise and present our observations on the effect of various types of noise on multi-photon protocols. We also investigate the effect of topologies such as ring, star, and torus on the noise characteristics of the multi-photon protocols. Our results show the possible advantages of switching to multi-photon protocols and give insights into the repeater placement and topology choice for quantum-augmented networks.

DOI
10.1117/12.3000586

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Quantum-augmented networks aim to use quantum phenomena to improve detection and protection against malicious actors in a classical communication network. This may include multiplexing quantum signals into classical fiber optical channels and incorporating purely quantum links alongside classical links in the network. In such hybrid networks, quantum protocols based on single photons become a bottleneck for transmission distances and data speeds, thereby reducing entire network performance. Furthermore, many of the security assumptions of the single-photon protocols do not hold up in practice because of the impossibility of manufacturing single-photon emitters. Multi-photon quantum protocols, on the other hand, are designed to operate under practical assumptions and do not require single photon emitters. As a result, they provide higher levels of security guarantees and longer transmission distances. However, the effect of channel and device noise on multiphoton protocols in terms of security, transmission distances, and bit rates has not been investigated. In this paper, we focus on channel noise and present our observations on the effect of various types of noise on multi-photon protocols. We also investigate the effect of topologies such as ring, star, and torus on the noise characteristics of the multi-photon protocols. Our results show the possible advantages of switching to multi-photon protocols and give insights into the repeater placement and topology choice for quantum-augmented networks.
Abstract Quantum key distribution (QKD) will most likely be an integral part of any practical quantum network setup in the future. However, not all QKD protocols can be used in today's networks because of the lack of single photon emitters and noisy intermediate quantum hardware. Attenuated photon transmission typically used to simulate single photon emitters severely limits the achievable transmission distances and the integration of QKD into existing classical networks that use tens of thousands of photons per bit of transmission. Furthermore, it has been found that different protocols perform differently in different network topologies. In order to remove the reliance of QKD on single photon emitters and increase transmission distances, it is worthwhile exploring QKD protocols that do not rely on single-photon transmissions for security, such as the 3-stage QKD protocol; the 3-stage protocol can tolerate multiple photons in each burst without leakage of information. This paper compares and contrasts the 3-stage QKD protocol and its efficiency in different network topologies and conditions. Further, we establish a mathematical relationship between achievable key rates for increasing transmission distances in various topologies. Our results provide insight to a network engineer in designing QKD networks of the future.
Quantum key distribution (QKD) will most likely be an integral part of any practical quantum network in the future. However, not all QKD protocols can be used in today’s networks because of the lack of single-photon emitters and noisy intermediate quantum hardware. Attenuated-photon transmission, typically used to simulate single-photon emitters, severely limits the achievable transmission distances and makes the integration of the QKD into existing classical networks, that use tens of thousands of photons per bit of transmission, difficult. Furthermore, it has been found that protocol performance varies with topology. In order to remove the reliance of QKD on single-photon emitters and increase transmission distances, it is worthwhile to explore QKD protocols that do not rely on single-photon transmissions for security, such as the 3-stage QKD protocol, which can tolerate multiple photons in each burst without information leakage. This paper compares and contrasts the 3-stage QKD protocol with conventional QKD protocols and its efficiency in different network topologies and conditions. Furthermore, we establish a mathematical relationship between achievable key rates to increase transmission distances in various topologies.
Aiming at the hybrid transmission of quantum signals and classical optical signals in the same networks, we analyze the noise interference of classical high-intensity optical signals on quantum signals to obtain the performance of the practical hybrid quantum-classical networks. With two common quantum key distribution protocols, BB84 and measurement-device-independent (MDI) protocol, we discuss the influence of the spontaneous Raman scattering noise from the classical optical signals and the insertion loss of the main network components on the quantum key generation rate, secure transmission distance and number of users of the networks. The numerical results show that under the same conditions, compared with the BB84 hybrid optical networks, the quantum signals in the MDI hybrid optical networks are more strongly interfered by the classical glare signals, and the performance degradation is more obvious. For the small and medium-sized access networks (the number of users does not exceed 31), the transmission distance of the MDI protocol is farther. For larger-scale networks, the key generation rate of the BB84 protocol is higher when the transmission distance does not exceed 46 km.
Near-term quantum networks face a bottleneck due to low quantum communication rates. This degrades performance both by lowering operating speeds and increasing qubit storage time in noisy memories, making some quantum internet applications infeasible. One way to circumvent this bottleneck is multiplexing: combining multiple signals into a single signal to improve the overall rate. Standard multiplexing techniques are classical in that they do not make use of coherence between quantum channels nor account for decoherence rates that vary during a protocol's execution. In this paper, we first derive semiclassical limits to multiplexing for many-qubit protocols and then introduce two techniques: single click quantum multiplexing and multiserver multiplexing. These can enable beyond-classical multiplexing advantages. We illustrate these techniques through three example applications: (1) entanglement generation between two asymetric quantum network nodes (i.e., repeaters or quantum servers with unequal memories), (2) remote state preparation between many end user devices and a single quantum node, and (3) remote state preparation between one end user device and many internetworked quantum nodes. By utilizing many noisy internetworked quantum devices instead of fewer low-noise devices, our multiplexing strategies enable new paths towards achieving high-speed many-qubit quantum network applications.
We present and compare the characteristic performance of single-photons, correlatedphotons, and entangled-photons for quantum key distribution over various fiber optic network topologies. The networks include the RING, BUS, and STAR. Quantum biterror rate is determined for each network as function of number of users, and transmission distance. The trade-off between number of users and transmission distance is presented. The robustness of the QKD against eavesdropping is evaluated for each architecture.
The efficacy of a communication network hinges upon both its physical architecture and the protocols that are employed within it. In the context of quantum communications, there exists a fundamental rate-loss trade-off for point-to-point quantum channels such that the rate for distributing entanglement, secret keys, or quantum states decays exponentially with respect to transmission distance. Quantum networks are the solution to overcome point-to-point limitations, but they simultaneously invite a challenging open question: How should quantum networks be designed to effectively and efficiently guarantee high rates? Now that performance and physical topology are inexorably linked, this question is not easy, but the answer is essential for a future quantum internet to be successful. In this work, we offer crucial insight into this open question for complex optical-fiber quantum networks. Using realistic descriptions of quantum networks via random network models and practical end-to-end routing protocols, we reveal critical phenomena associated with large-scale quantum networks. Our work reveals the weaknesses of applying single-path routing protocols within quantum networks, observing an inability to achieve reliable rates over long distances. Adapting algorithms for multipath routing, we employ an efficient and practical multipath routing algorithm capable of boosting performance while minimizing costly quantum resources.