Showing papers on "Coherent information published in 2020"
TL;DR: In this paper, the authors focus on the recent rapid developments of magnon-based hybrid systems, which seek to combine magnonic excitations with diverse excitations for transformative applications in devices, circuits, and information processing.
Abstract: Hybrid dynamic systems have recently gained interest with respect to both fundamental physics and device applications, particularly with their potential for coherent information processing. In this perspective, we will focus on the recent rapid developments of magnon-based hybrid systems, which seek to combine magnonic excitations with diverse excitations for transformative applications in devices, circuits, and information processing. Key to their promising potentials is that magnons are highly tunable excitations and can be easily engineered to couple with various dynamic media and platforms. The capability of reaching strong coupling with many different excitations has positioned magnons well for studying solid-state coherent dynamics and exploiting unique functionality. In addition, with their gigahertz frequency bandwidth and the ease of fabrication and miniaturization, magnonic devices and systems can be conveniently integrated into microwave circuits for mimicking a broad range of device concepts that have been applied in microwave electronics, photonics, and quantum information. We will discuss a few potential directions for advancing magnon hybrid systems, including on-chip geometry, novel coherent magnonic functionality, and coherent transduction between different platforms. As a future outlook, we will discuss the opportunities and challenges of magnonic hybrid systems for their applications in quantum information and magnonic logic.
146 citations
TL;DR: In this article, the authors focus on the recent rapid developments of magnon-based hybrid systems, which seek to combine magnonic excitations with diverse excitations for transformative applications in devices, circuits and information processing.
Abstract: Hybrid dynamic systems have recently gained interests with respect to both fundamental physics and device applications, particularly with their potential for coherent information processing In this perspective, we will focus on the recent rapid developments of magnon-based hybrid systems, which seek to combine magnonic excitations with diverse excitations for transformative applications in devices, circuits and information processing Key to their promising potentials is that magnons are highly tunable excitations and can be easily engineered to couple with various dynamic media and platforms The capability of reaching strong coupling with many different excitations has positioned magnons well for studying solid-state coherent dynamics and exploiting unique functionality In addition, with their gigahertz frequency bandwidth and the ease of fabrication and miniaturization, magnonic devices and systems can be conveniently integrated into microwave circuits for mimicking a broad range of device concepts that have been applied in microwave electronics, photonics and quantum information We will discuss a few potential directions for advancing magnon hybrid systems, including on-chip geometry, novel coherent magnonic functionality, and coherent transduction between different platforms As future outlook, we will discuss the opportunities and challenges of magnonic hybrid systems for their applications in quantum information and magnonic logic
105 citations
TL;DR: It is demonstrated that neural networkStates are capable of efficiently representing quantum codes for quantum information transmission and quantum error correction, supplying further evidence for the usefulness of neural network states to describe multipartite entanglement.
Abstract: We examine the usefulness of applying neural networks as a variational state ansatz for many-body quantum systems in the context of quantum information-processing tasks. In the neural network state ansatz, the complex amplitude function of a quantum state is computed by a neural network. The resulting multipartite entanglement structure captured by this ansatz has proven rich enough to describe the ground states and unitary dynamics of various physical systems of interest. In the present paper, we initiate the study of neural network states in quantum information-processing tasks. We demonstrate that neural network states are capable of efficiently representing quantum codes for quantum information transmission and quantum error correction, supplying further evidence for the usefulness of neural network states to describe multipartite entanglement. In particular, we show the following main results: a) Neural network states yield quantum codes with a high coherent information for two important quantum channels, the generalized amplitude damping channel and the dephrasure channel. These codes outperform all other known codes for these channels, and cannot be found using a direct parametrization of the quantum state. b) For the depolarizing channel, the neural network state ansatz reliably finds the best known codes given by repetition codes. c) Neural network states can be used to represent absolutely maximally entangled states, a special type of quantum error-correcting codes. In all three cases, the neural network state ansatz provides an efficient and versatile means as a variational parametrization of these highly entangled states.
53 citations
13 Feb 2020
TL;DR: In this article, the authors employed cavity resonator spectroscopy to demonstrate the complete control of the coupling strength of hybridized cavity-magnon states, and they used two driving microwave inputs which can be tuned at will.
Abstract: The full coherent control of hybridized systems such as strongly coupled cavity-magnon states is a crucial step to enable future information processing technologies. Thus, it is particularly interesting to engineer deliberate control mechanisms such as the full control of the coupling strength which can act as a measure for coherent information exchange. In this work, we employ cavity resonator spectroscopy to demonstrate the complete
control of the coupling strength of hybridized cavity-magnon states. For this, we use two driving microwave inputs which can be tuned at will. For these inputs, both the relative phase φ and relative amplitude ratio δ0 can be independently controlled. We demonstrate that for specific quadratures between both tones we can increase the coupling strength, close the anticrossing gap, and enter a regime of level merging. At the transition, the absolute cavity signal is modified by 30 dB and we observe an additional linewidth decrease of 13% at resonance level merging. This kind of control over the coupling, and hence linewidth, opens an avenue to enable or suppress an exchange of information and bridges the gap between quantum information and spintronics applications.
47 citations
TL;DR: An efficient alternating optimization algorithm is developed that can achieve competitive or better performance in comparison with some representative approaches for multiview representation learning and its convergence analysis is given.
Abstract: For many machine learning algorithms, their success heavily depends on data representation. In this paper, we present an ${\ell }_{2,1}$ -norm constrained canonical correlation analysis (CCA) model, that is, $ {L}_{{2,1}}$ -CCA, toward discovering compact and discriminative representation for the data associated with multiple views. To well exploit the complementary and coherent information across multiple views, the ${\ell }_{{2,1}}$ -norm is employed to constrain the canonical loadings and measure the canonical correlation loss term simultaneously. It enables, on the one hand, the canonical loadings to be with the capacity of variable selection for facilitating the interpretability of the learned canonical variables, and on the other hand, the learned canonical common representation keeps highly consistent with the most canonical variables from each view of the data. Meanwhile, the proposed ${L}_{{2,1}}$ -CCA can also be provided with the desired insensitivity to noise (outliers) to some degree. To solve the optimization problem, we develop an efficient alternating optimization algorithm and give its convergence analysis both theoretically and experimentally. Considerable experiment results on several real-world datasets have demonstrated that ${L}_{{2,1}}$ -CCA can achieve competitive or better performance in comparison with some representative approaches for multiview representation learning.
29 citations
TL;DR: An experimental approach to construct a dephrasure channel that contains both dephasing and erasure noises and can be used as an efficient tool to study the superadditivity of coherent information is presented.
Abstract: We present an experimental approach to construct a dephrasure channel that contains both dephasing and erasure noises and can be used as an efficient tool to study the superadditivity of coherent information. Using a three-fold dephrasure channel, the superadditivity of coherent information is observed, and a substantial gap is found between the zero single-letter coherent information and zero quantum capacity. Particularly, we find that, when the coherent information of n channel uses is zero, with a larger number of channel uses the quantum capacity becomes positive. These phenomena exhibit a more obvious superadditivity of coherent information than previous works and demonstrate a higher threshold for nonzero quantum capacity. Such novel channels built in our experiment also can provide a useful platform to study the nonadditive properties of coherent information and quantum channel capacity.
14 citations
TL;DR: In this paper, the positivity and nonadditivity of the one-letter quantum capacity (maximum coherent information) $Q^{(1)}$ was studied for two simple examples of complementary quantum channel pairs.
Abstract: The positivity and nonadditivity of the one-letter quantum capacity (maximum coherent information) $Q^{(1)}$ is studied for two simple examples of complementary quantum channel pairs $(B,C)$. They are produced by a process, we call it gluing, for combining two or more channels to form a composite. (We discuss various other forms of gluing, some of which may be of interest for applications outside those considered in this paper.) An amplitude-damping qubit channel with damping probability $0\leq p \leq 1$ glued to a perfect channel is an example of what we call a generalized erasure channel characterized by an erasure probability $\lambda$ along with $p$. A second example, using a phase-damping rather than amplitude-damping qubit channel, results in the dephrasure channel of Ledtizky et al. [Phys. Rev. Lett. 121, 160501 (2018)]. In both cases we find the global maximum and minimum of the entropy bias or coherent information, which determine $Q^{(1)}(B_g)$ and $Q^{(1)}(C_g)$, respectively, and the ranges in the $(p,\lambda)$ parameter space where these capacities are positive or zero, confirming previous results for the dephrasure channel. The nonadditivity of $Q^{(1)}(B_g)$ for two channels in parallel occurs in a well defined region of the $(p,\lambda)$ plane for the amplitude-damping case, whereas for the dephrasure case we extend previous results to additional values of $p$ and $\lambda$ at which nonadditivity occurs. For both cases, $Q^{(1)}(C_g)$ shows a peculiar behavior: When $p=0$, $C_g$ is an erasure channel with erasure probability $1-\lambda$, so $Q^{(1)}(C_g)$ is zero for $\lambda \leq 1/2$. However, for any $p>0$, no matter how small, $Q^{(1)}(C_g)$ is positive, though it may be extremely small, for all $\lambda >0$. Despite the simplicity of these models we still lack an intuitive understanding of the nonadditivity of $Q^{(1)}(B_g)$ and the positivity of $Q^{(1)}(C_g)$.
13 citations
Posted Content•
TL;DR: In this article, the authors counterintuitively boost the quantum capacity of a channel by leaking almost all quantum information to the channel's environment, which exploits two-letter level non-additivity in the quantum channel's coherent information.
Abstract: Entanglement lies at the root of quantum theory. It is a remarkable resource that is generally believed to diminish when entangled systems interact with their environment. On the contrary, we find that engaging a system with its environment increases its ability to retain entanglement. The maximum rate of retaining entanglement is given by the quantum channel capacity. We counter-intuitively boost the quantum capacity of a channel by leaking almost all quantum information to the channel's environment. This boost exploits two-letter level non-additivity in the channel's coherent information. The resulting non-additivity has a far larger magnitude and a qualitatively wider extent than previously known. Our findings have a surprising implication for quantum key distribution: maximum rates for key distribution can be boosted by allowing leakage of information to the eavesdropping environment.
10 citations
01 Jun 2020
TL;DR: The convergence analysis is based on quantum entropy inequalities and leads to a priori additive ε-approximations after $\mathcal{O}\left( {{\varepsilon ^{ - 1}}\log N} \right)$ iterations, where N denotes the input dimension of the channel.
Abstract: We generalize alternating optimization algorithms of Blahut-Arimoto type to the quantum setting. In particular, we give iterative algorithms to compute the mutual information of quantum channels, the thermodynamic capacity of quantum channels, the coherent information of less noisy quantum channels, and the Holevo quantity of classical-quantum channels. Our convergence analysis is based on quantum entropy inequalities and leads to a priori additive e-approximations after $\mathcal{O}\left( {{\varepsilon ^{ - 1}}\log N} \right)$ iterations, where N denotes the input dimension of the channel. We complement our analysis with an a posteriori stopping criterion which allows us to terminate the algorithm after significantly fewer iterations compared to the a priori criterion in numerical examples. Finally, we discuss heuristics to accelerate the convergence.
8 citations
TL;DR: The properties of squeezing in relation to the different interaction frequencies of the input modes in three-mode Kerr nonlinear coupler consisting of two linearly-coupled Kerr waveguides were examined in this article.
Abstract: The properties of squeezing, in relation to the different interaction frequencies of the input modes in three-mode Kerr nonlinear coupler consisting of two linearly-coupled Kerr waveguides, were ex...
6 citations
TL;DR: In this article, the authors show that this phenomenon can be modeled on the basis of the recently developed social laser theory, which can be used to model stimulated amplification of coherent social actions, such as mass protests to votes and other collective decisions.
Abstract: During the last years our society was often exposed to the coherent information waves of high amplitudes. These are waves of huge social energy. Often they are of the destructive character, a kind of information tsunami. But, they can carry as well positive improvements in the human society, as waves of decision making matching rational recommendations of societal institutes. The main distinguishing features of these waves are their high amplitude, coherence (homogeneous character of social actions generated by them), and short time needed for their generation and relaxation. Such waves can be treated as large scale exhibition of the Bandwagon effect. We show that this socio-psychic phenomenon can be modeled on the basis of the recently developed {\it social laser theory}. This theory can be used to model {\it stimulated amplification of coherent social actions}. "Actions" are treated very generally, from mass protests to votes and other collective decisions, as, e.g., acceptance (often unconscious) of some societal recommendations. In this paper, we concentrate on theory of laser resonators, physical vs. social. For the latter, we analyze in very detail functioning of the internet based Echo-Chambers. Their main purpose is increasing of the power of the quantum information field as well as its coherence. Of course, the Bandwagon effect is well known and well studied in social psychology. However, the social laser theory gives the possibility to model it by using the general formalism of quantum field theory. The paper contains minimum of mathematics and it can be readable by researchers working in psychology, cognitive, social, and political sciences; it might also be interesting for experts in information theory and artificial intelligence.
Posted Content•
TL;DR: A small linear increase from zero in some eigenvalue of a density operator makes the derivative of its von-Neumann entropy logarithmic, a $\log$-singularity, and methods for checking non-additivity and positivity of the coherent information of a noisy quantum channel are developed.
Abstract: A small linear increase from zero in some eigenvalue of a density operator makes the derivative of its von-Neumann entropy logarithmic. We call this logarithmic derivative a $\log$-singularity and use it develop methods for checking non-additivity and positivity of the coherent information $\mathcal{Q}^{(1)}$ of a noisy quantum channel. One concrete application of our method leads to a novel type of non-additivity where a zero quantum capacity qubit amplitude damping channel in parallel with a simple qutrit channel is shown to have larger $\mathcal{Q}^{(1)}$ than the sum of $\mathcal{Q}^{(1)}$'s of the two individual channels. Another application shows that any noisy quantum channel has positive $\mathcal{Q}^{(1)}$ if its output dimension is larger than its complementary output (environment) dimension and this environment dimension equals the rank of some output state obtained from a pure input state. Special cases of this result prove $\mathcal{Q}^{(1)}$ is positive for a variety of channels, including the complement of a qubit channel, and a large family of incomplete erasure channels where the positivity of $\mathcal{Q}^{(1)}$ comes as a surprise.
Journal Article•
TL;DR: In this paper, the authors propose an equation alternative to Bekenstein's from the viewpoint of quantum information, rather than thermodynamics, to resolve this inconsistency without changing Hawking's original proposal for the radiation.
Abstract: Bekenstein argued that black holes should have entropy proportional to their areas to make black hole physics compatible with the second law of thermodynamics. However, the heuristic picture for Hawking radiation, creation of pairs of positive- and negative-energy particles, leads to an inconsistency among the first law of black hole mechanics, Bekenstein's argument and quantum mechanics. In this paper we propose an equation alternative to Bekenstein's from the viewpoint of quantum information, rather than thermodynamics, to resolve this inconsistency without changing Hawking's original proposal for the radiation. This argues that the area of a black hole is proportional to the coherent information, which is minus the conditional entropy, defined only in the quantum regime, from the outside, to positive-energy particles inside it. This hints that negative-energy particles inside a black hole behave as if they have negative entropy. Our result suggests that the black holes store pure quantum information, rather than classical information.
Dissertation•
01 Jan 2020
TL;DR: In this paper, the authors show that a socio-psychic phenomenon can be modeled based on the recently developed social laser theory, which can be used to model stimulated amplification of coherent social actions.
Abstract: During recent years our society has often been exposed to coherent information waves of high amplitudes. These are waves of huge social energy. Often they are of destructive character, a kind of information tsunami. However, they can also carry positive improvements in human society, as waves of decision-making matching rational recommendations of societal institutes. The main distinguishing features of these waves are their high amplitude, coherence (homogeneous character of social actions generated by them), and short time needed for their generation and relaxation. Such waves can be treated as large-scale exhibitions of the bandwagon effect. We show that this socio-psychic phenomenon can be modeled based on the recently developed social laser theory. This theory can be used to model stimulated amplification of coherent social actions. “Actions” are treated very generally, from mass protests to votes and other collective decisions, such as, e.g., acceptance (often unconscious) of some societal recommendations. In this paper, we concentrate on the theory of laser resonators, physical vs. social. For the latter, we analyze in detail the functioning of Internet-based echo chambers. Their main purpose is increasing of the power of the quantum information field as well as its coherence. Of course, the bandwagon effect is well known and well studied in social psychology. However, social laser theory gives the possibility to model it by using general formalism of quantum field theory. The paper contains the minimum of mathematics and it can be read by researchers working in psychological, cognitive, social, and political sciences; it might also be interesting for experts in information theory and artificial intelligence.
TL;DR: In this article, the possibility of organizing multiuser access based on the differentially coherent information transmission scheme using chaotic radio pulses as data carriers has been demonstrated, and theoretical estimates for the maximum number of subscribers and the information capacity of a multi-user system were made.
Abstract: The possibility of organizing multiuser access based on the differentially coherent information transmission scheme using chaotic radio pulses as data carriers has been demonstrated. Some theoretical estimates were made for the maximum number of subscribers and the information capacity of a multiuser system. Computer-aided modeling was performed to validate the obtained theoretical results.
TL;DR: In this article, the authors prove a general theorem concerning positivity of a channel's coherent information and apply it to all qubit channels whose complement has non-zero capacity, and show that changes in entropy caused by this singularity are responsible for both positivity and non-additivity of the coherent information.
Abstract: When can noiseless quantum information be sent across noisy quantum devices? And at what maximum rate? These questions lie at the heart of quantum technology, but remain unanswered because of non-additivity -- a fundamental synergy which allows quantum devices (aka quantum channels) to send more information than expected. Previously, non-additivity was known to occur in very noisy channels with coherent information much smaller than that of a perfect channel; but, our work shows non-additivity in a simple low-noise channel. Our results extend even further. We prove a general theorem concerning positivity of a channel's coherent information. A corollary of this theorem gives a simple dimensional test for a channel's capacity. Applying this corollary solves an open problem by characterizing all qubit channels whose complement has non-zero capacity. Another application shows a wide class of zero quantum capacity qubit channels can assist an incomplete erasure channel in sending quantum information. These results arise from introducing and linking logarithmic singularities in the von-Neumann entropy with quantum transmission: changes in entropy caused by this singularity are a mechanism responsible for both positivity and non-additivity of the coherent information. Analysis of such singularities may be useful in other physics problems.