We revisit the practical implementation of high-dimensional quantum key distribution protocol using path entanglement reported in [Phys.Rev.Lett.~127,~110505,~2021]. Here we refine the noise robustness analysis performed there by simulating the effect of different types of channel noise on the noiseless experimental data. Further, we extend the analysis to two kinds of asymmetric scenarios. In the first scenario the entanglement source is placed in Alice's lab and thus Only one noisy channel has to be considered. In the second scenario, Bob's detectors are placed at different physical locations and therefore such scenario implements a simple communication network. Our analysis can also be extended to other experimental platforms and therefore provides a novel framework for fair noise robustness comparison of high-dimensional quantum key distribution protocols.
We revisit the practical implementation of high-dimensional quantum key distribution protocol using path entanglement reported in [Phys.Rev.Lett.~127,~110505,~2021]. Here we refine the noise robustness analysis performed there by simulating the effect of different types of channel noise on the noiseless experimental data. Further, we extend the analysis to two kinds of asymmetric scenarios. In the first scenario the entanglement source is placed in Alice's lab and thus Only one noisy channel has to be considered. In the second scenario, Bob's detectors are placed at different physical locations and therefore such scenario implements a simple communication network. Our analysis can also be extended to other experimental platforms and therefore provides a novel framework for fair noise robustness comparison of high-dimensional quantum key distribution protocols.
Quantum cryptography has emerged as a rapidly advancing field in recent years and represents one of the first practical applications of quantum physics beyond purely theoretical research. Despite its potential, current quantum cryptographic systems remain highly sensitive to noise. High- dimensional implementations offer a promising strategy to en- hance robustness. In this work, we investigate high-dimensional quantum key distribution protocols. Particular emphasis is placed on maritime communication scenarios, where harsh environ- mental conditions, atmospheric turbulence, and platform motion introduce significant noise and instability.
We investigate the resilience to noise of single-qubit quantum key distribution (QKD) protocols in the scenario of security against independent eavesdropping attacks and key distillation based on one-way classical communication. To this end, we introduce a noise-based metric that quantifies the efficiency of QKD protocols. Within this framework, we analyze the maximal noise levels that allow Alice and Bob to asymptotically establish a secure secret key. Using this assumption, we compare the noise tolerance of general single-qubit QKD protocols, in particular the BB84, B92, E91, and six-state protocols. Our main result determines the noise level threshold for QKD allowing one to distill an asymptotically secure secret key. Additionally, we demonstrate that the six-state protocol achieves the greatest resistance to noise while simultaneously yielding a higher post-selection efficiency than the other analyzed single-qubit protocols, confirming its robustness within the considered security model. Finally, we perform an analysis of the proposed noise-based metric and the conventional quantum bit error rate (QBER) metric.
The idea of semi-quantum communication protocols provides a theoretical solution for the high costs of quantum resources. In this study, we propose an efficient semi-quantum key distribution protocol that allows Alice and quantum-capable restricted Bob to establish a secure key. Then, we demonstrate that the protocol is information-theoretic secure in the asymptotic scenario. As long as the channel noise is less than the noise tolerance of the protocol, Alice and Bob can withdraw a secure key. The proposed protocol has advantages over previous protocols regarding qubit efficiency and communication cost. Besides, our efficiency analysis is more fair and practical because noise factors are taken into account. Based on these features, it may have potential applications in future quantum communications.
Abstract Discrete-variable (DV) and continuous-variable (CV) schemes constitute the two major families of quantum key distribution (QKD) protocols. Unfortunately, since the setup elements required by these schemes are quite different, making a fair comparison of their potential performance in particular applications is often troublesome, limiting the experimenters’ capability to choose an optimal solution. In this work we perform a general comparison of the major entanglement-based DV and CV QKD protocols in terms of their resistance to the channel noise, with the otherwise perfect setup, showing the definite superiority of the DV family. We analytically derive fundamental bounds on the tolerable channel noise and attenuation for entanglement-based CV QKD protocols. We also investigate the influence of DV QKD setup imperfections on the obtained results in order to determine benchmarks for the parameters of realistic photon sources and detectors, allowing the realistic DV protocols to outperform even the ideal CV QKD analogs. Our results indicate the realistic advantage of DV entanglement-based schemes over their CV counterparts and suggests the practical efforts for maximizing this advantage.
Quantum key distribution(QKD) is an important area in quantum information theory. There are two kinds of QKD protocols, one is so-called prepare-measure protocols and the other is entanglement-based protocols. For long-distance communications in a noisy environment, entangled-based protocols might be more reliable since they could be supplied by distilled procedures which protect them from noises. In this paper, entanglement-based QKD over certain noisy channels are discussed. We give schemes against collective noises, including collective dephasing(CD) and collective rotation(CR), Pauli noises, amplitude damping(AD) noises, phase damping(PD) noises and mixtures of them. Our discussions are in a direction about how to implement a QKD protocol over noisy channels as in a noiseless channels with no errors, in theoretical. Also, we analyse the efficiency of our schemes, demonstrating that they could be more efficient than the standard entanglement-based QKD scheme.
Quantum communication is at the heart of the quantum information theory. We study two types of quantum communication protocols over noisy transmission channels, i.e. super dense coding and cryptography protocols. In the first part of this thesis, for various scenarios, it is discussed how the super dense coding capacity is influenced by noisy quantum channels. The case of memoryless channels as well as those channels with memory which are modelled by uncorrelated and correlated noise, respectively, are considered. Explicitly Pauli channels over arbitrary dimensions are treated and the super dense coding capacity for some resource states is derived. For the qubit depolarizing channel, when noise is uncorrelated, the super dense coding capacity with respect to the input state is also optimized. This illustrates a threshold value of the noise parameter below which the super dense coding capacity is optimized by a maximally entangled initial state, while above the threshold value the super dense coding capacity is optimized by a product state. For Pauli channels, with correlated noise, the case of non unitary encoding is studied and the super dense coding capacity is derived. The first part of this thesis is concluded with an example for multipartite super dense coding.
In the second part of the thesis, the problem of optimal eavesdropping on noisy states in quantum key distribution is investigated. The case of the six state protocol, when the signal states are mixed with white noise, is considered. This situation may arise either when Alice deliberately adds noise to the signal states before they leave her lab, or, in a realistic scenario when the eavesdropper (referred to as Eve) is not assumed to replace the noisy quantum channel by a noiseless one. For individual attacks, we find Eve's optimal mutual information with Alice as a function of the quantum bit error rate. Finally, the results illustrate that adding noise on the quantum level can make quantum key distribution more robust against eavesdropping.