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Coherent information
About: Coherent information is a research topic. Over the lifetime, 1225 publications have been published within this topic receiving 46672 citations.
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28 Dec 1999
TL;DR: It was shown that the calculated coherent information is equal to zero for all types of the full measurement procedures, whereas it completely preserves its value for the quantum duplication procedure.
Abstract: The coherent information concept is used to analyze a variety of simple quantum systems. Coherent information was calculated for the information decay in a two-level atom in the presence of an external resonant field, for the information exchange between two coupled two-level atoms, and for the information transfer from a two-level atom to another atom and to a photon field. The coherent information is shown to be equal to zero for all full-measurement procedures, but it completely retains its original value for quantum duplication. Transmission of information from one open subsystem to another one in the entire closed system is analyzed to learn quantum information about the forbidden atomic transition via a dipole active transition of the same atom. It is argued that coherent information can be used effectively to quantify the information channels in physical systems where quantum coherence plays an important role.
3 citations
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03 Oct 2005
TL;DR: The paper is devoted to consideration of a number of recently published results, possessing a conceptual feature, and related with attempts of generalization of the notion of "entropy".
Abstract: The paper is devoted to consideration of a number of recently published results, possessing, in main, a conceptual feature, and related with attempts of generalization of the notion of "entropy". It has been shown the attempts to be scientific delusions. A correct variant of a generalized description for the entropy within the framework is proposed.
3 citations
TL;DR: In this paper, it was shown that the noise threshold for classical advantage distillation of a specific kind is substantially lower than the threshold for quantum entanglement distillation if the eavesdropper can perform powerful coherent attacks.
Abstract: The security of a cryptographic key that is generated by communication through a noisy quantum channel relies on the ability to distill a shorter secure key sequence from a longer insecure one. We show that - for protocols that use quantum channels of any dimension and completely characterize them by state tomography - the noise threshold for classical advantage distillation of a specific kind is substantially lower than the threshold for quantum entanglement distillation if the eavesdropper can perform powerful coherent attacks. In marked contrast, earlier investigations had shown that the thresholds are identical for incoherent attacks on the same classical distillation scheme. It remains an open question whether other schemes for classical advantage distillation have higher thresholds for coherent eavesdropping attacks.
3 citations
12 Jul 2021
TL;DR: In this paper, a generalization of quantum polar codes to quantum channels with qudit-input, achieving the symmetric coherent information of the channel, was proposed, which relies on channel combining and splitting construction, where a two-qudit unitary randomly chosen from a unitary 2-design is used to combine two instances of a qudit input channel.
Abstract: We provide a generalization of quantum polar codes to quantum channels with qudit-input, achieving the symmetric coherent information of the channel. Our scheme relies on a channel combining and splitting construction, where a two-qudit unitary randomly chosen from a unitary 2-design is used to combine two instances of a qudit-input channel. The inputs to the synthesized bad channels are frozen by sharing EPR pairs between the sender and the receiver, so our scheme is entanglement assisted. Using the fact that the generalized two-qudit Clifford group forms a unitary 2-design, we conclude that the channel combining operation can be chosen from this set. Moreover, we show that polarization also happens for a much smaller subset of two-qudit Cliffords, which is not a unitary 2-design. Finally, we show how to decode the proposed quantum polar codes on Pauli qudit channels.
3 citations
07 Nov 2002
TL;DR: A modified variational model based on the coherent diffusion for enhancing SNR is proposed, using the coherence in the difference image as a feedback to re-estimate diffusivities in places where coherent leakage was detected.
Abstract: Anisotropic diffusion has proved efficiency in filtering wide range of images. However, its application to improve SNR in MR images was limited due to the minute details existing in many medical image modalities e.g., MR and CT images. Therefore, these types of images require sophisticated sensitive filtering methods. In this paper we propose a modified variational model based on the coherent diffusion for enhancing SNR. The difference between the filtered and the degraded image may contain some residual coherent information. This coherent information means that the applied diffusion parameters in these areas were overestimated. In this paper, the coherence in the difference image is used as a feedback to re-estimate diffusivities in places where coherent leakage was detected. Results show that information associated with resolved-object structure, even minute structures, were substantially preserved.
3 citations