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Laser Physics

Improving the capacity of quantum dense coding via non-Hermitian operation

Yang Leng, Fei Chen

Published Nov 7, 2023• 9 citations
Publisher

Abstract

Abstract We propose a novel method to enhance the capacity of quantum dense coding under amplitude damping noise using non-Hermitian operations. With the assistance of non-Hermitian operations, we show that the capacity of quantum dense coding can always be larger than 1 for any two-qubit states. In particular, the non-Hermitian operation can improve quantum dense coding more efficiently in the case of strong decoherence strength than those with small decoherence strength. Our results shed new light on the protection of quantum dense coding in a quantum environment.

DOI
10.1088/1555-6611/ad06a1

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Abstract We propose a novel method to enhance the capacity of quantum dense coding under amplitude damping noise using non-Hermitian operations. With the assistance of non-Hermitian operations, we show that the capacity of quantum dense coding can always be larger than 1 for any two-qubit states. In particular, the non-Hermitian operation can improve quantum dense coding more efficiently in the case of strong decoherence strength than those with small decoherence strength. Our results shed new light on the protection of quantum dense coding in a quantum environment.
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Abstract Using the non-Hermitian operation approach, the enhanceable capacity of quantum dense coding can be realized in the quantum spin chain channel. We derive the exact analytical expressions of the quantum dense coding and in detail investigate the influence of non-Hermitian operator parameters on the quantum dense coding. We find that the non-Hermitian operator process can obviously enhance the quantum dense coding. In particular, we show that the optimal capacity of quantum dense coding can always be larger than 1 with the assistance of non-Hermitian operations.
Abstract Entangled states with high-dimensional systems have been investigated widely because of their extended possibilities. We investigate the entanglement protection of a qubit–qutrit system under amplitude damping decoherence by employing non-Hermitian operation. We find that the qubit–qutrit entanglement decays monotonically as the decoherence strength increases, and may go through a sudden death for strong decoherence strength. However, we can completely defeat amplitude damping decoherence and recover or even magnify the initial entanglement perfectly by means of non-Hermitian operation. In particular, the non-Hermitian operation can protect entanglement more efficiently in the case of strong decoherence strength than those with small decoherence strength.
Quantum dense coding enables the transmission of two classical bits of information through the exchange of a single qubit, provided that an entangled state is shared between the communicating parties. While this protocol achieves a fundamental increase in channel capacity, its practical realization is strongly influenced by the presence of noise in realistic quantum channels. This work presents a simulation-based study of dense coding performance under two representative noise models: the depolarizing channel and the amplitude damping channel. Using Qiskit Aer, the bit error rate (BER), frame error rate (FER), and effective channel capacity are evaluated across a range of noise parameters. In addition, a classical threefold repetition strategy is examined as a lightweight error-mitigation technique. Results indicate that depolarizing noise produces more rapid degradation in both BER and channel capacity compared to amplitude damping, while repetition coding provides partial improvement in reliability at the expense of resource overhead. These findings highlight the trade-offs between efficiency and robustness in noisy implementations of dense coding and motivate further exploration of more advanced quantum error correction methods.