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arXiv:2611.01732

Decoherence suppression in quantum dense coding

Xi Yan, Wen-Jie Zhang, Jun-Hong An

quant-phSubmitted Nov 1, 2026• Announced Nov 3, 2026
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Abstract

By harnessing entanglement to transmit information beyond the limits of classical communication, quantum dense coding serves as a key component in various quantum technologies. However, in the noisy intermediate-scale quantum era, noise-induced decoherence poses inevitable challenges to its practical implementation. By investigating the non-Markovian decoherence dynamics of the two categories of quantum dense coding protocols realized in discrete- and continuous-variable systems, we demonstrate a physical mechanism to suppress the decoherence in quantum dense coding. It is found that the formation of a bound state in the energy spectrum of the entire system consisting of each subsystem and its local environment of the quantum channel restores the quantum advantage of dense coding in the presence of decoherence. Refreshing our understanding on the noisy effect on quantum dense coding, our finding offers a guide toward the practical realization of noise-tolerant quantum dense coding.

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Quantum dense coding of continuous variables via a two-mode squeezed vacuum state is considered for a noisy quantum channel. Classical information is encoded in the two quadrature components of one mode of a two-mode squeezed vacuum state and the encoded mode is sent through a noisy quantum channel which is assumed to be linearly dissipative. Decoding at the receiver side is performed by simultaneous measurement of two quadrature components of the two-mode state. By calculating the error probability of a binary communication system, we examine whether the dense coding is effective or not when a quantum channel is noisy.
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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.