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Entropy

Enhanced Superdense Coding over Correlated Amplitude Damping Channel

Yan‐Ling Li, Dong-Mei Wei, Chuanjin Zu, Xing Mao Xiao

Published Jun 16, 2019• 8 citations
Publisher

Abstract

Quantum channels with correlated effects are realistic scenarios for the study of noisy quantum communication when the channels are consecutively used. In this paper, superdense coding is reexamined under a correlated amplitude damping (CAD) channel. Two techniques named as weak measurement and environment-assisted measurement are utilized to enhance the capacity of superdense coding. The results show that both of them enable us to battle against the CAD decoherence and improve the capacity with a certain probability. Remarkably, the scheme of environment-assisted measurement always outperforms the scheme of weak measurement in both improving the capacity and successful probability. These notable superiorities could be attributed to the fact that environment-assisted measurement can extract additional information from the environment and thus it performs much better.

DOI
10.3390/e21060598

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Quantum channels with correlated effects are realistic scenarios for the study of noisy quantum communication when the channels are consecutively used. In this paper, superdense coding is reexamined under a correlated amplitude damping (CAD) channel. Two techniques named as weak measurement and environment-assisted measurement are utilized to enhance the capacity of superdense coding. The results show that both of them enable us to battle against the CAD decoherence and improve the capacity with a certain probability. Remarkably, the scheme of environment-assisted measurement always outperforms the scheme of weak measurement in both improving the capacity and successful probability. These notable superiorities could be attributed to the fact that environment-assisted measurement can extract additional information from the environment and thus it performs much better.
From the perspective of quantum information transmission, one may be interested in the teleportation of quantum Fisher information (QFI) which provides the optimal precision of parameter estimation. In this paper, we investigate the teleportation of QFI under the correlated amplitude damping (CAD) decoherence. It is found that the correlated effects play a positive role in improving the teleported QFI, but the impact of decoherence is still serious. Therefore, we propose two schemes, which are based on weak measurement (WM) and environment-assisted measurement (EAM), to enhance the teleportation of QFI under the CAD decoherence. The results show that both schemes can significantly improve the teleported QFI with a certain success probability. The findings of our study suggest that the correlated effects can significantly increase the success probabilities of these two schemes. A detailed comparison confirms that the EAM scheme is more efficient than the WM scheme in improving the teleportation of QFI.
Abstract We study the performance of high-dimensional superdense coding (HD-SDC) over an amplitude damping (AD) channel with memory and propose a protocol that leverages partial measurement and its reversal to enhance the channel capacity. By considering a two-qutrit system, we model the memory AD noise using a convex mixture of memoryless and perfectly memory AD channels. We demonstrate that the memory effect alone can mitigate the decay of the SDC capacity under noise. More significantly, we show that the application of partial measurement before the channel and its reversal after the channel can not only recover the capacity degraded by noise but, for certain non-maximally entangled initial states, even amplify it beyond the initial capacity. This amplification effect is governed by three key factors: the ground-state probability in the initial entangled state, the memory strength, and the partial measurement strength. Our results provide a practical strategy for enhancing quantum communication protocols in realistic noisy environments and highlight the synergistic benefits of memory noise and measurement-based control.
The generalized amplitude damping (GAD) noise models the dynamical map of a qubit in contact with a non-zero temperature bosonic reservoir. When two qubits successively pass through the same GAD channel, correlation effects should be taken into account. Therefore, the dynamical map is modeled as correlated GAD (CGAD) noise. In this paper, we investigate the teleportation of quantum Fisher information (QFI) under CGAD noise. We first show that the correlation effects in CGAD noise can enhance the teleported QFI. We then present two probabilistic schemes to improve the teleportation of QFI in CGAD noise by weak measurement (WM) and environment-assisted measurement (EAM). We find the correlation effects of CGAD noise serve to improve the teleportation of QFI and increase the probability of success. Contrary to intuition, the thermal average photon number n doesn't always play a negative role in our probabilistic schemes. Although a larger n will cause the QFI to decay faster, the corresponding probability of success will be higher. Finally, we introduce a quantity called average QFI to demonstrate that the EAM scheme is superior to the WM scheme with respect to QFI improvement under CGAD noise.
Abstract We introduce an escort-qubit–assisted protocol that restores and stabilizes superdense coding capacity in the presence of amplitude damping channel (ADC) noise. The protocol is analyzed under three fundamental noisy configurations: amplitude damping acting on Alice’s subsystem, on Bob’s subsystem, and on both subsystems covering all practically relevant scenarios. In the absence of protection, we show that ADC effects cause a monotonic degradation of the superdense coding capacity, driving it below the classical limit in the strong decoherence regime and completely erasing the quantum advantage. Our escort-qubit protocol overcomes this limitation by coherently tracking the channel-induced Kraus trajectories during entanglement distribution. Post-selection of the no-flip trajectory, projects the shared state onto a maximally entangled resource state, thereby recovering the optimal superdense coding capacity of two classical bits, independent of the noise strength and noisy configuration. Importantly, when all ADC trajectories are taken into account, the resulting average capacity although inherently suboptimal remains strictly above both the classical limit and the unprotected capacity across the entire decoherence range. These results establish the escort-qubit protocol as a powerful, scalable, and experimentally viable approach for preserving quantum advantage and enhancing information throughput in noisy quantum communication networks.
Quantum communication protocols, such as superdense coding, offer significant advantages in information transfer by leveraging quantum entanglement. However, practical implementations are hindered by the presence of noise and decoherence in quantum systems. This study investigates the effectiveness of the Steane 7-qubit error correction code in mitigating the impact of noise on the superdense coding protocol. Simulations were performed using Qiskit Aer, incorporating depolarizing, amplitude damping, and phase damping noise models at varying strengths. The error rates were evaluated across multiple trials to assess the robustness of the encoded communication. The results demonstrate that the Steane code substantially improves the fidelity of information transmission, with varying levels of protection depending on the type of noise present. These findings contribute to a better understanding of error correction strategies for reliable quantum communication in noisy environments.