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.
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.
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.
Quantum dense coding could be used to transmit two classical bits with one qubit when a maximally entangled state is shared. In realistic channels, entanglement degradation reduces the channel capacity, while bit-flip noise increases decoding errors. To address these issues, we propose a novel probabilistic controlled dense coding protocol that employs the three-qubit repetition code for error correction and an auxiliary qubit for probabilistic decoding. Moreover, this proposed scheme includes a third party to supervise the communication based on a three-qubit entanglement state. The implementation steps of our protocol are presented in detail, and numerical simulations show that it achieves higher average information than dense coding without error correction. The scheme provides a robust solution for quantum communication under noisy conditions and non-maximally entangled state.
Quantum communication protocols such as superdense coding enable high-capacity information transfer using quantum entanglement. However, their performance is significantly affected by environmental noise and decoherence. This study presents an enhanced simulation framework for evaluating the Steane 7-qubit error correction code applied to superdense coding under realistic noise conditions. Building upon earlier models, the proposed work introduces robust circuit depth control mechanism and noise-aware simulation using Qiskit Aer to analyze depolarizing, amplitude damping, and phase damping errors. The system automatically encodes, decodes, and measures fidelity across varying noise probabilities, classifying results into performance tiers based on resilience. Comprehensive visualization through trend plots, heatmaps, and tier distributions offers clear insights into the impact of noise on quantum communication fidelity. The findings demonstrate that Steane encoding stabilizes fidelity within moderate noise levels, thereby improving the robustness of dense coding. This enhanced model provides a reproducible and scalable approach for studying quantum error correction, contributing to the design of noise-tolerant quantum communication networks.
Quantum computing holds immense promise for revolutionizing various fields, but its inherent susceptibility to noise poses a significant challenge to achieving reliable computations. This work investigates the degradation of quantum information due to noise and proposes an optimized approach to error-correcting codes specifically tailored for quantum systems. We establish a precise noise degradation model, incorporating various noise types and their statistical properties, represented as (σi). This model allows for a more realistic simulation of quantum noise compared to traditional approaches. Subsequently, we employ an optimization algorithm, based on the principle of minimizing bit-flip error rates, to design error-correcting codes. The core of our design strategy leverages information theory concepts, particularly channel capacity and mutual information, represented as (Cch, Imn), to determine the optimal code parameters. The optimization process aims to find the most efficient code that can effectively protect quantum information from noise, ultimately enhancing the reliability of quantum computations. The final optimized code is characterized by its encoding rate (R), decoding rate (D), and the minimum distance (dmin) of the code, represented as (R, D, dmin). The results demonstrate the effectiveness of our approach in mitigating noise degradation and improving the performance of quantum error correction.
We consider the fundamental protocol of dense coding of classical information assuming that noise affects both the forward and backward communication lines between Alice and Bob. Assuming that this noise is described by the same quantum channel, we define its dense coding capacity by optimizing over all adaptive strategies that Alice can implement, while Bob encodes the information by means of Pauli operators. Exploiting techniques of channel simulation and protocol stretching, we are able to establish the dense coding capacity of Pauli channels in arbitrary finite dimension, with simple formulas for depolarizing and dephasing qubit channels.
We introduce noise-adaptive quantum key distribution (QKD) protocols, in which the honest parties optimize the encoding (state preparation) and decoding (measurement basis) operations according to the noise models affecting the honest subsystems induced by an eavesdropper. This extends conventional QKD schemes that employ fixed encoding and decoding strategies independent of the noise characteristics of the communication channel. We investigate three representative protocols: entanglement-based secure dense coding (SDC), the entanglement-free Lucamarini and Mancini (LM05), and a two-way prepare-and-measure Bennett Brassard (BB84) protocols. Using entropic uncertainty relations, we derive the corresponding secret key rates for both adaptive and conventional non-adaptive scenarios under collective attacks. For independent but identical noise acting on the forward and backward transmission channels, as well as for correlated and non-Markovian environments, we identify classes of channels for which adaptive schemes yield enhanced secret key rates for the considered protocols. In contrast, we also determine Pauli channels, including depolarizing and bit flip channels, for which adaptive strategies provide no benefit. We further show that these optimal sets are generally non-unique and can differ substantially from the unitaries that maximize dense-coding capacity in the absence of security constraints. Our results establish noise-adaptive encoding and decoding as a powerful framework for improving secure communication over realistic noisy quantum channels.