Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Journal of the Physical Society of Japan

Non-Equilibrium Dynamics of Quantum Dense Coding Process

Tomoko Yonemura, Sachiko Kitajima, Fumiaki Shibata

Published Apr 15, 2004• 8 citations
Publisher

Abstract

Theory of quantum mechanical communication channel under the influence of environmental fluctuations is formulated on the basis of non-equilibrium statistical mechanics. The formalism is explicitly applied to the quantum dense coding process where a qubit signal is sent into the channel in which the temperature and/or quantum fluctuations disturb an initial coherency of the signal. A quantum channel matrix, the Shannon's mutual information and quantum mechanical mutual information are analytically obtained and numerically evaluated. It is shown that the temperature effect is quite large in the signal transmission processes.

DOI
10.1143/jpsj.73.855

Related papers

Dynamics of Quantum Fluctuations in a Communication Channel –Quantum Dense Coding–

Sachiko Kitajima

The dynamics of a quantum dense coding process is formulated and exactly solved on the basis of a boson detector model previously used to study decoherence processes. When classical information encoded in entangled states is transmitted through a quantum mechanical communication channel, an environment exerts quantum noise causing decoherence and disentanglement. Shannon's mutual information and error probability function are obtained explicitly as functions of time.

Journal of the Physical Society of Japan•May 15, 2004•5 citations

A Model of Quantum Mechanical Communication Channel with Quantum and Thermal Noises

Sachiko Kitajima, Masashi Ban, Fumiaki Shibata

Dynamics of quantum information channel is studied with the use of a boson detector model. Explicit results are given for quantum dense coding process on the basis of an equivalence relation between a classical capacity and von Neumann mutual information. Reduced density matrices for an entangled spin degree of freedom of an incoming particle are exactly solved to give complete time evolution under influence of fluctuations due to a detector. Quantum mechanical channel matrix and the classical capacity are determined as functions of time and temperature. Decoherence properties of the entangled states under quantum and thermal noises are fully discussed.

Journal of the Physical Society of Japan•May 15, 2005•1 citation

Decoherence of entanglement in the Bloch channel

Masashi Ban, Sachiko Kitajima, Fumiaki Shibata

Decoherence of entanglement of qubits is investigated which is caused by the phenomenological quantum channel (the Bloch channel) equivalent to the Bloch equations. It is shown how the decoherence of entanglement depends on the longitudinal and transverse relaxation times and the equilibrium value of the qubit. The quantum dense coding system under the influence of the Bloch channel is also investigated. The Shannon mutual information obtained by the Bell measurement and the Holevo capacity is calculated. Furthermore, the microscopic system-reservoir model which yields the Bloch equations is considered. The result shows that the temperature of the thermal reservoir significantly affects the decoherence of entanglement.

Journal of Physics A Mathematical and General•Apr 25, 2005•23 citations

Quantum communication via noisy channels

Z. Shadman

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.

•Jan 1, 2011•0 citations

Quantum channels and memory effects

Filippo Caruso, Vittorio Giovannetti, Cosmo Lupo +1 more

Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allow one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far has been focused on the case in which a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appear to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory and other branches of physics. A survey is taken of the field of quantum channels theory while also embracing these specific and complex settings.

arXiv:1207.5435•Reviews of Modern Physics•Dec 10, 2014•329 citations

Decoherence suppression in quantum dense coding

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

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.

quant-pharXiv:2611.01732•Nov 3, 2026
Theory of quantum mechanical communication channel under the influence of environmental fluctuations is formulated on the basis of non-equilibrium statistical mechanics. The formalism is explicitly applied to the quantum dense coding process where a qubit signal is sent into the channel in which the temperature and/or quantum fluctuations disturb an initial coherency of the signal. A quantum channel matrix, the Shannon's mutual information and quantum mechanical mutual information are analytically obtained and numerically evaluated. It is shown that the temperature effect is quite large in the signal transmission processes.
Dynamics of quantum information channel is studied with the use of a boson detector model. Explicit results are given for quantum dense coding process on the basis of an equivalence relation between a classical capacity and von Neumann mutual information. Reduced density matrices for an entangled spin degree of freedom of an incoming particle are exactly solved to give complete time evolution under influence of fluctuations due to a detector. Quantum mechanical channel matrix and the classical capacity are determined as functions of time and temperature. Decoherence properties of the entangled states under quantum and thermal noises are fully discussed.
Decoherence of entanglement of qubits is investigated which is caused by the phenomenological quantum channel (the Bloch channel) equivalent to the Bloch equations. It is shown how the decoherence of entanglement depends on the longitudinal and transverse relaxation times and the equilibrium value of the qubit. The quantum dense coding system under the influence of the Bloch channel is also investigated. The Shannon mutual information obtained by the Bell measurement and the Holevo capacity is calculated. Furthermore, the microscopic system-reservoir model which yields the Bloch equations is considered. The result shows that the temperature of the thermal reservoir significantly affects the decoherence of entanglement.
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.
Any physical process can be represented as a quantum channel mapping an initial state to a final state. Hence it can be characterized from the point of view of communication theory, i.e., in terms of its ability to transfer information. Quantum information provides a theoretical framework and the proper mathematical tools to accomplish this. In this context the notion of codes and communication capacities have been introduced by generalizing them from the classical Shannon theory of information transmission and error correction. The underlying assumption of this approach is to consider the channel not as acting on a single system, but on sequences of systems, which, when properly initialized allow one to overcome the noisy effects induced by the physical process under consideration. While most of the work produced so far has been focused on the case in which a given channel transformation acts identically and independently on the various elements of the sequence (memoryless configuration in jargon), correlated error models appear to be a more realistic way to approach the problem. A slightly different, yet conceptually related, notion of correlated errors applies to a single quantum system which evolves continuously in time under the influence of an external disturbance which acts on it in a non-Markovian fashion. This leads to the study of memory effects in quantum channels: a fertile ground where interesting novel phenomena emerge at the intersection of quantum information theory and other branches of physics. A survey is taken of the field of quantum channels theory while also embracing these specific and complex settings.
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.