Faculty Profiles - HAYASHI Masahito

Papers - HAYASHI Masahito

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Capacity of Quantum Private Information Retrieval with Colluding Servers Reviewed International coauthorship

2020.6

Asymptotic properties for Markovian dynamics in quantum theory and general probabilistic theories Reviewed International coauthorship

Yoshida Y., Hayashi M.

Journal of Physics A: Mathematical and Theoretical Vol. 53 ( 21 ) 2020.5

Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Physics A: Mathematical and Theoretical

We address asymptotic decoupling in the context of Markovian quantum dynamics. Asymptotic decoupling is an asymptotic property on a bipartite quantum system, and asserts that any correlation between two quantum systems is broken after a sufficiently long time passes. In this paper, we show that asymptotic decoupling is equivalent to local mixing which asserts the convergence to a unique stationary state on at least one quantum system. If dynamics is asymptotically decoupling, any correlation between two quantum systems is broken exponentially. Also, we give a criterion of mixing that is a system of linear equations. All results in this paper are proved in the framework of general probabilistic theories, but we also summarize them in quantum theory.

DOI： 10.1088/1751-8121/ab8599

Scopus

Two-Way Physical Layer Security Protocol for Gaussian Channels Reviewed International coauthorship

Hayashi M., Vazquez-Castro Á.

IEEE Transactions on Communications Vol. 68 ( 5 ) page： 3068 - 3078 2020.5

Authorship：Lead author Language：English Publishing type：Research paper (scientific journal) Publisher：IEEE Transactions on Communications

In this paper we propose a two-way protocol of physical layer security using the method of privacy amplification against eavesdroppers. First we justify our proposed protocol by analyzing the physical layer security provided by the classic wiretap channel model (i.e. one-way protocol). In the Gaussian channels, the classic one-way protocol requires Eve's channel to be degraded w.r.t. Bob's channel. However, this channel degradation condition depends on Eve's location and whether Eve's receiving antenna is more powerful than Bob's. To overcome this limitation, we introduce a two-way protocol inspired in IEEE TIT (1993) that eliminates the channel degradation condition. In the proposed two-way protocol, on a first phase, via Gaussian channel, Bob sends randomness to Alice, which is partially leaked to Eve. Then, on a second phase, Alice transmits information to Bob over a public noiseless channel. We derive the secrecy capacity of the two-way protocol when the channel to Eve is also Gaussian. We show that the capacity of the two-way protocol is always positive. We present numerical values of the capacities illustrating the gains obtained by our proposed protocol. We apply our result to simple yet realistic models of satellite communication channels.

DOI： 10.1109/TCOMM.2020.2973618

Scopus

Finite-Length Analyses for Source and Channel Coding on Markov Chains. Reviewed International coauthorship

Hayashi M, Watanabe S

Entropy (Basel, Switzerland) Vol. 22 ( 4 ) 2020.4

Authorship：Lead author,　Corresponding author Language：English Publishing type：Research paper (scientific journal) Publisher：Entropy

We derive finite-length bounds for two problems with Markov chains: source coding with side-information where the source and side-information are a joint Markov chain and channel coding for channels with Markovian conditional additive noise. For this purpose, we point out two important aspects of finite-length analysis that must be argued when finite-length bounds are proposed. The first is the asymptotic tightness, and the other is the efficient computability of the bound. Then, we derive finite-length upper and lower bounds for the coding length in both settings such that their computational complexity is low. We argue the first of the above-mentioned aspects by deriving the large deviation bounds, the moderate deviation bounds, and second-order bounds for these two topics and show that these finite-length bounds achieve the asymptotic optimality in these senses. Several kinds of information measures for transition matrices are introduced for the purpose of this discussion.

DOI： 10.3390/e22040460

Scopus

PubMed

Application of the Resource Theory of Channels to Communication Scenarios. Reviewed International coauthorship

Takagi R, Wang K, Hayashi M

Physical review letters Vol. 124 ( 12 ) page： 120502 2020.3