Country：Japan

Award type：Award from international society, conference, symposium, etc.  Country：China

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： https://doi.org/10.22331/q-2023-03-02-936

DOI： https://doi.org/10.22331/q-2023-03-02-936

Other Link： https://doi.org/10.22331/q-2023-03-02-936

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

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：APS  

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

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：IEEE  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Nature  

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

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

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

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

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

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevApplied.16.054021

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2021.3077269

Scopus

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT45174.2021.9517794

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TCOMM.2021.3067907

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2021.3064009

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2021.3060452

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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

DOI： 10.1109/TCOMM.2021.3057112

Scopus

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

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

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

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

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2020.3022515

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：EPJ Quantum Technology  

Quantum private information retrieval (QPIR) for quantum messages is a quantum communication task, in which a user retrieves one of the multiple quantum states from the server without revealing which state is retrieved. In the one-server setting, we find an exponential gap in the communication complexities between the presence and absence of prior entanglement in this problem with the one-server setting. To achieve this aim, as the first step, we prove that the trivial solution of downloading all messages is optimal under QPIR for quantum messages, which is a similar result to that of classical PIR but different from QPIR for classical messages. As the second step, we propose an efficient one-server one-round QPIR protocol with prior entanglement by constructing a reduction from a QPIR protocol for classical messages to a QPIR protocol for quantum messages in the presence of prior entanglement.

DOI： 10.1140/epjqt/s40507-024-00266-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quantum Science and Technology  

Quantum information bottleneck was proposed by Grimsmo and Still (2016 Phys. Rev. A 94 012338) as a promising method for quantum supervised machine learning. To study this method, we generalize the quantum Arimoto-Blahut algorithm by Ramakrishnan et al (2021 IEEE Trans. Inf. Theory 67 946) to a function defined over a set of density matrices with linear constraints so that our algorithm can be applied to optimizations of quantum operations. This algorithm has wider applicability, and we apply our algorithm to the quantum information bottleneck with three quantum systems. We numerically compare our obtained algorithm with the existing algorithm by Grimsmo and Still. Our numerical analysis shows that our algorithm is better than their algorithm.

DOI： 10.1088/2058-9565/ad6eb1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：New Journal of Physics  

In quantum theory, a quantum state on a composite system of two parties realizes a non-negative probability with any measurement element with a tensor product form. However, there also exist non-quantum states which satisfy the above condition. Such states are called beyond-quantum states, and cannot be detected by standard Bell tests. To distinguish a beyond-quantum state from quantum states, we propose a measurement-device-independent (MDI) test for beyond-quantum state detection, which is composed of quantum input states on respective parties and quantum measurements across the input system and the target system on respective parties. The performance of our protocol is independent of the forms of the tested states and the measurement operators, which provides an advantage in practical scenarios. We also discuss the importance of tomographic completeness of the input sets to the detection.

DOI： 10.1088/1367-2630/ad787c

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：International Journal of Quantum Information  

This paper reviews Holevo's contributions to quantum information theory during the 20 century. At that time, he mainly studied three topics, classical-quantum channel coding, quantum estimation with Craméro-Rao approach and quantum estimation with the group covariant approach. This paper addresses these three topics.

DOI： 10.1142/S0219749924400069

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review A  

We study the detection of beyond-quantum nonlocal states that can exist in a theoretical model whose local systems are standard quantum theory in the framework of general probabilistic theories (GPTs). We find that device-dependent detections are possible for beyond-quantum nonlocal states in GPTs even though device-independent detections are not valid. We give a device-dependent detection based on local observables to distinguish any beyond-quantum nonlocal state from all standard quantum states. In particular, we give a way to detect any beyond-quantum nonlocal state of the two-qubit system by observing only spin observables on local systems. Our results will help in the experimental detection of beyond-quantum nonlocality or justification of standard quantum theory.

DOI： 10.1103/PhysRevA.110.L010201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

This paper studies the secrecy results for the two-way wiretap channel (TW-WC) with an external eavesdropper under a strong secrecy metric. Employing non-adaptive coding, we analyze the information leakage and the decoding error probability, and derive inner bounds on the secrecy capacity regions for the TW-WC under strong joint and individual secrecy constraints. For the TW-WC without cost constraint, both the secrecy and error exponents could be characterized by the conditional Rényi mutual information in a concise and compact form. And, some special cases secrecy capacity region and sum-rate capacity results are established, demonstrating that adaption is useless in some cases or the maximum sum-rate that could be achieved by non-adaptive coding. For the TW-WC with cost constraint, we consider the peak cost constraint and extend our secrecy results by using the constant composition codes. Accordingly, we characterize both the secrecy and error exponents by a modification of Rényi mutual information, which yields inner bounds on the secrecy capacity regions for the general discrete memoryless TW-WC with cost constraint. Our method works even when a pre-noisy processing is employed based on a conditional distribution in the encoder and can be easily extended to other multi-user communication scenarios.

DOI： 10.1109/TIT.2023.3343362

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Ramanujan Journal  

We introduce a certain discrete probability distribution Pn,m,k,l;q having non-negative integer parameters n, m, k, l and quantum parameter q which arises from a zonal spherical function of the Grassmannian over the finite field Fq with a distinguished spherical vector. Using representation theoretic arguments and hypergeometric summation technique, we derive the presentation of the probability mass function by a single q-Racah polynomial, and also the presentation of the cumulative distribution function in terms of a terminating 4ϕ3-hypergeometric series.

DOI： 10.1007/s11139-024-00859-w

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Letters in Mathematical Physics  

We discuss dense coding with n copies of a specific preshared state between the sender and the receiver when the encoding operation is limited to the application of group representation. Typically, to act on multiple local copies of these preshared states, the receiver needs quantum memory, because in general the multiple copies will be generated sequentially. Depending on available encoding unitary operations, we investigate what preshared state offers an advantage of using quantum memory on the receiver’s side.

DOI： 10.1007/s11005-024-01831-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：New Journal of Physics  

It is a key issue to characterize the model of standard quantum theory out of general models by an operational condition. The framework of general probabilistic theories (GPTs) is a new information theoretical approach to single out standard quantum theory. It is known that traditional properties, for example, Bell-CHSH inequality, are not sufficient to single out standard quantum theory among possible models in GPTs. As a more precise property, we focus on the bound of the performance for an information task called state discrimination in general models. We give an equivalent condition for outperforming the minimum discrimination error probability under the standard quantum theory given by the trace norm. Besides, by applying the equivalent condition, we characterize standard quantum theory out of general models in GPTs by the bound of the performance for state discrimination.

DOI： 10.1088/1367-2630/ad4d18

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Advanced Quantum Technologies  

Oblivious transfer is considered as a cryptographic primitive task for quantum information processing over a quantum network. It is an essential building block for secure multiparty computation. It is known that one-server oblivious transfer is impossible. When the task is the transmission of classical messages, protocols for two-server oblivious transfer exist, i.e., existing protocols work under the assumption that two servers do not communicate with each other. However, when the task is the transmission of a quantum state, no existing method works even under the above two-server assumption. Two-server oblivious transfer protocols for quantum messages are proposed for the first time.

DOI： 10.1002/qute.202300184

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

There exists a gap for the proofs of the converse parts of (49) and (50) in Theorem 1 and (74) of Theorem 3. These converse parts use Lemma 4, whose proofs contain a gap. We fix these errors when the rate is larger than the critical rate. A special case of (50) does not coincide the recent result (Li and Yao, 2022, arXiv:2209.00554v1) when the rate is smaller than the critical rate.

DOI： 10.1109/TIT.2024.3355506

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

We propose a covert communication protocol for the spread-spectrum multiple random access with additive white Gaussian noise (AWGN) channel. No existing paper has studied covert communication for the random access channel. Our protocol assumes binary discrete phase-shift keying (BPSK) modulation, and it works well under imperfect channel state information (I-CSI) for both the legitimate and adversary receivers, which is a realistic assumption in the low power regime. Also, our method assumes that the legitimate users share secret variables in a similar way as the preceding studies. Although several studies investigated the covert communication for the point-to-point communication, no existing paper considers the covert communication under the above uncertainty assumption even for point-to-point communication. Our protocol under the above uncertainty assumption allows O(n) legitimate senders and O(n/n) active legitimate senders. Furthermore, our protocol can be converted to a protocol for point-to-point communication that works under the above uncertainty assumption.

DOI： 10.1109/TCOMM.2023.3332861

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE/ACM Transactions on Networking  

Secret sharing is a useful method for secure distributed data storage. Such a distributed data storage can avoid the information leakage under an attack to a limited number of distributed servers. While such distributed servers send their shares to an end user according to the request, there is a risk that malicious distributed servers send incorrect shares. To detect or identify such malicious servers, we need verifiable secure distributed data storage, which can be constructed from verifiable secret sharing. However, many of previous protocols for verifiable secret sharing are constructed in a specific form. This paper proposes an adaptive construction of verifiable secret sharing, which uses an existing secret sharing protocol as a subprotocol. Also, our method can be applied to any existing secret sharing protocol. This type construction realizes an economical construction.

DOI： 10.1109/TNET.2023.3283577

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Information Geometry  

Iterative minimization algorithms appear in various areas including machine learning, neural networks, and information theory. The em algorithm is one of the famous iterative minimization algorithms in the area of machine learning, and the Arimoto–Blahut algorithm is a typical iterative algorithm in the area of information theory. However, these two topics had been separately studied for a long time. In this paper, we generalize an algorithm that was recently proposed in the context of the Arimoto–Blahut algorithm. Then, we show various convergence theorems, one of which covers the case when each iterative step is done approximately. Also, we apply this algorithm to the target problem of the em algorithm, and propose its improvement. In addition, we apply it to other various problems in information theory.

DOI： 10.1007/s41884-024-00140-5

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Information Geometry  

The recent paper (IEEE Trans. IT 69, 1680) proposed an analytical calculation method for the channel capacity without iteration. However, it has restrictions for its application. Also, it does not explain why the channel capacity can be solved analytically in this special case. To expand the applicability of this method, we recall the reverse em-problem, which was proposed by Toyota (Information Geometry, 3, 1355 (2020)) as the repetition of the inverse map of the em iteration to calculate the channel capacity, which is given as the maximum of the mutual information. However, it left several open problems. We formulate the reverse em-problem based on Bregman divergence, and solve these open problems. Using these results, we convert the reverse em-problem into em-problems, and derive a non-iterative formula for the reverse em-problem, which can be considered as a generalization of the above analytical calculation method. Additionally, this derivation explains the information geometrical structure of this special case.

DOI： 10.1007/s41884-024-00147-y

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：npj Quantum Information  

Blind quantum computation (BQC) is a secure quantum computation method that protects the privacy of clients. Measurement-based quantum computation (MBQC) is a promising approach for realizing BQC. To obtain reliable results in blind MBQC, it is crucial to verify whether the resource graph states are accurately prepared in the adversarial scenario. However, previous verification protocols for this task are too resource-consuming or noise-susceptible to be applied in practice. Here, we propose a robust and efficient protocol for verifying arbitrary graph states with any prime local dimension in the adversarial scenario, which leads to a robust and efficient protocol for verifying the resource state in blind MBQC. Our protocol requires only local Pauli measurements and is thus easy to realize with current technologies. Nevertheless, it can achieve optimal scaling behaviors with respect to the system size and the target precision as quantified by the infidelity and significance level, which has never been achieved before. Notably, our protocol can exponentially enhance the scaling behavior with the significance level.

DOI： 10.1038/s41534-023-00783-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

After completing the review process of the above article, the author found the reference Muroga (1953), which has already derived an analytical calculation method for the channel capacity under a certain condition. This comment explains the relation between Muroga's article and this article.

DOI： 10.1109/TIT.2023.3299885

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

This paper unifiedly addresses two kinds of key quantum secure tasks, i.e., quantum versions of secret sharing (SS) and symmetric private information retrieval (SPIR) by using multi-target monotone span program (MMSP), which characterizes the classical linear protocols of SS and SPIR. SS has two quantum extensions; One is the classical-quantum (CQ) setting, in which the secret to be sent is classical information and the shares are quantum systems. The other is the quantum-quantum (QQ) setting, in which the secret to be sent is a quantum state and the shares are quantum systems. The relation between these quantum protocols and MMSP has not been studied sufficiently. We newly introduce the third setting, i.e., the entanglement-assisted (EA) setting, which is defined by modifying the CQ setting with allowing prior entanglement between the dealer and the end-user who recovers the secret by collecting the shares. Showing that the linear version of SS with the EA setting is directly linked to MMSP, we characterize linear quantum versions of SS with the CQ ad QQ settings via MMSP. Further, we introduce the EA setting of SPIR, which is shown to link to MMSP. In addition, we discuss the quantum version of maximum distance separable codes.

DOI： 10.1109/TIT.2023.3282940

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

We study commitment scheme for classical-quantum channels. To accomplish this we define various notions of commitment capacity for these channels and prove matching upper and lower bound on it in terms of the conditional entropy. Our achievability (lower bound) proof is quantum generalisation of the work of one of the authors (arXiv:2103.11548) which studied the problem of secure list decoding and its application to bit-string commitment. The techniques we use in the proof of converse (upper bound) is similar in spirit to the techniques introduced by Winter, Nascimento and Imai (Cryptography and Coding 2003) to prove upper bound on the commitment capacity of classical channels. However, generalisation of this technique to the quantum case is not so straightforward and requires some new constructions, which can be of independent interest.

DOI： 10.1109/TIT.2023.3268321

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

We formulate em algorithm in the framework of Bregman divergence, which is a general problem setting of information geometry. That is, we address the minimization problem of the Bregman divergence between an exponential subfamily and a mixture subfamily in a Bregman divergence system. Then, we show the convergence and its speed under several conditions. We apply this algorithm to rate distortion and its variants including the quantum setting, and show the usefulness of our general algorithm. In fact, existing applications of Arimoto-Blahut algorithm to rate distortion theory make the optimization of the weighted sum of the mutual information and the cost function by using the Lagrange multiplier. However, in rate distortion theory, it is needed to minimize the mutual information under the constant constraint for the cost function. Our algorithm directly solves this minimization. In addition, we have numerically checked the convergence speed of our algorithm in the classical case of rate distortion problem.

DOI： 10.1109/TIT.2023.3239955

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

We derive an analytical algorithm for the channel capacity of a classical channel without any iteration, while its existing algorithms require iterations and the number of iterations depends on the required precision level. Hence, our algorithm is its first analytical algorithm for this task without any iteration, while this algorithm needs several conditions for the channel. We apply the obtained algorithm to examples, and see how the obtained algorithm works in these examples. Then, we extend it to the channel capacity of a classical-quantum (cq-) channel. Many existing studies proposed algorithms for a cq-channel and all of them require iterations. Our extended analytical algorithm has also no iteration, and outputs the exactly optimum value.

DOI： 10.1109/TIT.2022.3215178

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

The max-relative entropy together with its smoothed version is a basic tool in quantum information theory. In this paper, we derive the exact exponent for the asymptotic decay of the small modification of the quantum state in smoothing the max-relative entropy based on purified distance. We then apply this result to the problem of privacy amplification against quantum side information, and we obtain an upper bound for the exponent of the asymptotic decreasing of the insecurity, measured using either purified distance or relative entropy. Our upper bound complements the earlier lower bound established by Hayashi, and the two bounds match when the rate of randomness extraction is above a critical value. Thus, for the case of high rate, we have determined the exact security exponent. Following this, we give examples and show that in the low-rate case, neither the upper bound nor the lower bound is tight in general. This exhibits a picture similar to that of the error exponent in channel coding. Lastly, we investigate the asymptotics of equivocation and its exponent under the security measure using the sandwiched Rényi divergence of order s (1,2] , which has not been addressed previously in the quantum setting.

DOI： 10.1109/TIT.2022.3217671

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quantum  

The ability to extract relevant information is critical to learning. An ingenious approach as such is the information bottleneck, an optimisation problem whose solution corresponds to a faithful and memory-efficient representation of relevant information from a large system. The advent of the age of quantum computing calls for efficient methods that work on information regarding quantum systems. Here we address this by proposing a new and general algorithm for the quantum generalisation of information bottleneck. Our algorithm excels in the speed and the definiteness of convergence compared with prior results. It also works for a much broader range of problems, including the quantum extension of deterministic information bottleneck, an important variant of the original information bottleneck problem. Notably, we discover that a quantum system can achieve strictly better performance than a classical system of the same size regarding quantum information bottleneck, providing new vision on justifying the advantage of quantum machine learning.

DOI： 10.22331/q-2023-03-02-936

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：New Journal of Physics  

An experimental verification of the maximally entangled state ensures that the constructed state is close to the maximally entangled state, but it does not guarantee that the state is exactly the same as the maximally entangled state. Further, the entanglement structure is not uniquely determined in general probabilistic theories even if we impose that the local subsystems are fully equal to quantum systems. Therefore, the existence of the maximally entangled state depends on whether the standard entanglement structure (SES) is valid. To examine this issue, we introduce pseudo SES as a structure of quantum composite system under natural assumptions based on the existence of projective measurements and the existence of approximations of all maximally entangled standard states. Surprisingly, there exist infinitely many pseudo SESs different from the SES. In our setting, any maximally entangled state can be arbitrarily approximated by an entangled state that belongs to our obtained pseudo standard entanglement structure. That is, experimental verification does not exclude the possibility of our obtained pseudo standard entanglement structure that is different from the standard entanglement structure. On the other hand, such pseudo structures never possess global unitary symmetry, i.e. global unitary symmetry is essential condition for the SES.

DOI： 10.1088/1367-2630/acb565

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quantum  

In the quest to unlock the maximum potential of quantum sensors, it is of paramount importance to have practical measurement strategies that can estimate incompatible parameters with best precisions possible. However, it is still not known how to find practical measurements with optimal precisions, even for uncorrelated measurements over probe states. Here, we give a concrete way to find uncorrelated measurement strategies with optimal precisions. We solve this fundamental problem by introducing a framework of conic programming that unifies the theory of precision bounds for multiparameter estimates for uncorrelated and correlated measurement strategies under a common umbrella. Namely, we give precision bounds that arise from linear programs on various cones defined on a tensor product space of matrices, including a particular cone of separable matrices. Subsequently, our theory allows us to develop an efficient algorithm that calculates both upper and lower bounds for the ultimate precision bound for uncorrelated measurement strategies, where these bounds can be tight. In particular, the uncorrelated measurement strategy that arises from our theory saturates the upper bound to the ultimate precision bound. Also, we show numerically that there is a strict gap between the previous efficiently computable bounds and the ultimate precision bound.

DOI： 10.22331/Q-2023-08-29-1094

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PRX Quantum  

We investigate practical dense coding by imposing locality restrictions on decoders and symmetry restrictions on encoders within the resource theory of asymmetry framework. In this task, the sender Alice and the helper Fred preshare an entangled state. Alice encodes a classical message into the quantum state using a symmetric preserving encoder and sends the encoded state to Bob through a noiseless quantum channel. The receiver Bob and helper Fred are limited to performing quantum measurements satisfying certain locality restrictions to decode the classical message. We are interested in the ultimate dense coding capacity under these constraints. Our contributions are summarized as follows. First, we derive both one-shot and asymptotic optimal achievable transmission rates of the dense coding task under different encoder and decoder combinations. Surprisingly, our results reveal that the transmission rate cannot be improved even when the decoder is relaxed from one-way local operations and classical communication (LOCC) to two-way LOCC, separable measurements, and partial transpose positive measurements of the bipartite system. Second, depending on the class of allowed decoders with certain locality restrictions, we relax the class of encoding operations to superquantum encoders in the general probability theory framework and derive dense coding transmission rates under this setting. For example, when the decoder is fixed to a separable measurement, theoretically, a positive operation is allowed as an encoding operation. Remarkably, even under this superquantum relaxation, the transmission rate still cannot be lifted. This fact highlights the universal validity of our analysis on practical dense coding beyond quantum theory.

DOI： 10.1103/PRXQuantum.3.030346

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PRX Quantum  

Self-testing is a technology to certify states and measurements using only the statistics of the experiment. Self-testing is possible if some extremal points in the set BQ of quantum correlations for a Bell experiment are achieved, up to isometries, with specific states and measurements. However, BQ is difficult to characterize, so it is also difficult to prove whether or not a given matrix of quantum correlations allows for self-testing. Here, we show how some tools from graph theory can help to address this problem. We observe that BQ is strictly contained in an easy-to-characterize set associated with a graph, Θ(G). Therefore, whenever the optimum over BQ and the optimum over Θ(G) coincide, self-testing can be demonstrated by simply proving self-testability with Θ(G). Interestingly, these maxima coincide for the quantum correlations that maximally violate many families of Bell-like inequalities. Therefore, we can apply this approach to prove the self-testability of many quantum correlations, including some that are not previously known to allow for self-testing. In addition, this approach connects self-testing to some open problems in discrete mathematics. We use this connection to prove a conjecture [M. Araújo et al., Phys. Rev. A, 88, 022118 (2013)] about the closed-form expression of the Lovász theta number for a family of graphs called the Möbius ladders. Although there are a few remaining issues (e.g., in some cases, the proof requires the assumption that measurements are of rank 1), this approach provides an alternative method to self-testing and draws interesting connections between quantum mechanics and discrete mathematics.

DOI： 10.1103/PRXQuantum.3.030344

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quantum Information Processing  

We propose a new cryptographic resource, secure modulo zero-sum randomness, as a resource to implement a task of secure modulo summation, and its quantum protocol. Secure modulo summation is the calculation of modulo summation Y1+ ⋯ + Ym when m players have their individual variables Y1, … , Ym with keeping the secrecy of the individual variables. Secure modulo zero-sum randomness is a set of m variables X1, … , Xm held by m players that satisfy the zero sum condition X1+ ⋯ + Xm= 0 with a certain security condition. This paper explains the relation between these two concepts and proposes a quantum verifiable protocol for secure modulo summation. The advantage for quantum protocol is the verifiability based on self-testing, which does not need to trust measurement devices and can be realized by using a statistical concept, significance level, while any classical method needs to trust several components of the protocol. Then, we propose various cryptographic applications for secure modulo zero-sum randomness. We also compare our quantum verifiable protocol with the conventional method for secure modulo summation.

DOI： 10.1007/s11128-022-03639-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：npj Quantum Information  

Complex processes often arise from sequences of simpler interactions involving a few particles at a time. These interactions, however, may not be directly accessible to experiments. Here we develop the first efficient method for unravelling the causal structure of the interactions in a multipartite quantum process, under the assumption that the process has bounded information loss and induces causal dependencies whose strength is above a fixed (but otherwise arbitrary) threshold. Our method is based on a quantum algorithm whose complexity scales polynomially in the total number of input/output systems, in the dimension of the systems involved in each interaction, and in the inverse of the chosen threshold for the strength of the causal dependencies. Under additional assumptions, we also provide a second algorithm that has lower complexity and requires only local state preparation and local measurements. Our algorithms can be used to identify processes that can be characterized efficiently with the technique of quantum process tomography. Similarly, they can be used to identify useful communication channels in quantum networks, and to test the internal structure of uncharacterized quantum circuits.

DOI： 10.1038/s41534-022-00578-4

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Applied  

We study quantum secure direct communication using a general preshared quantum state and a generalization of dense coding. In this scenario, Alice is allowed to apply a unitary operation on the preshared state to encode her message, and the set of allowed unitaries forms a group. To decode the message, Bob is allowed to apply a measurement across his system and the system he receives. In the worst scenario, we guarantee that Eve obtains no information for the message even when Eve accesses the joint system between the system that she intercepts and her original system of the preshared state. For a practical application, we propose a concrete protocol and derive an upper bound of information leakage in the finite-length setting. We also discuss how to apply our scenario to the case with discrete Weyl-Heisenberg representation when the preshared state is unknown.

DOI： 10.1103/PhysRevApplied.17.064011

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2022.3150498

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Quantum Science and Technology  

Heisenberg scaling characterizes the ultimate precision of parameter estimation enabled by quantum mechanics, which represents an important quantum advantage of both theoretical and technological interest. Here, we present a comprehensive and rigorous study of the attainability of strong, global notions of Heisenberg scaling (in contrast to the commonly studied local estimation based on e.g. quantum Fisher information) in the fundamental problem of quantum metrology, in noisy environments. As our first contribution, we formally define two useful notions of Heisenberg scaling in global estimation respectively based on the average estimation error and the limiting distribution of estimation error (which we highlight as a practically important figure of merit). A main result of this work is that for the standard phase damping noise, an O(n -1) noise rate is a necessary and sufficient condition for attaining global Heisenberg scaling. We first prove that O(n -1) is an upper bound on the noise rate for Heisenberg scaling to be possible, and then show by constructing a 'robust' estimation procedure that global Heisenberg scaling in both senses can indeed be achieved under Θ(n -1) noise. In addition, we provide a practically more friendly adaptive protocol using only an one-qubit memory, which achieves global Heisenberg scaling in terms of limiting distribution as well under O(n -1) noise.

DOI： 10.1088/2058-9565/ac5d7e

Web of Science

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Journal on Selected Areas in Communications  

We study the equivalence between non-perfect secret sharing (NSS) and symmetric private information retrieval (SPIR) with arbitrary response and collusion patterns. NSS and SPIR are defined with an access structure, which corresponds to the authorized/forbidden sets for NSS and the response/collusion patterns for SPIR. We prove the equivalence between NSS and SPIR in the following two senses. 1) Given any SPIR protocol with an access structure, an NSS protocol is constructed with the same access structure and the same rate. 2) Given any linear NSS protocol with an access structure, a linear SPIR protocol is constructed with the same access structure and the same rate. We prove the first relation even if the SPIR protocol has imperfect correctness and secrecy. From the first relation, we derive an upper bound of the SPIR capacity for arbitrary response and collusion patterns. For the special case of \mathsf {n} -server SPIR with \mathsf {r} responsive and \mathsf {t} colluding servers, this upper bound proves that the SPIR capacity is (\mathsf {r}-\mathsf {t})/\mathsf {n}. From the second relation, we prove that a SPIR protocol exists for any response and collusion patterns.

DOI： 10.1109/JSAC.2022.3142375

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Journal on Selected Areas in Communications  

In quantum private information retrieval (QPIR), a user retrieves a classical file from multiple servers by downloading quantum systems without revealing the identity of the file. The QPIR capacity is the maximal achievable ratio of the retrieved file size to the total download size. In this paper, the capacity of QPIR from MDS-coded and colluding servers is studied for the first time. Two general classes of QPIR, called stabilizer QPIR and dimension-squared QPIR induced from classical strongly linear PIR are defined, and the related QPIR capacities are derived. For the non-colluding case, the general QPIR capacity is derived when the number of files goes to infinity. A general statement on the converse bound for QPIR with coded and colluding servers is derived showing that the capacities of stabilizer QPIR and dimension-squared QPIR induced from any class of PIR are upper bounded by twice the classical capacity of the respective PIR class. The proposed capacity-achieving scheme combines the star-product scheme by Freij-Hollanti et al. and the stabilizer QPIR scheme by Song et al. by employing (weakly) self-dual Reed-Solomon codes.

DOI： 10.1109/JSAC.2022.3142363

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2021.3131575

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.105.022419

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3150/21-BEJ1344

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Scopus

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3390/e24010047

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Access  

Inspired by quantum key distribution, we consider wireless communication between Alice and Bob when the noise generated in the intermediate space between Alice and Bob is controlled by Eve. Our model divides the channel noise into two parts, the noise generated during the transmission and the noise generated in the detector. Eve is allowed to control the former, but is not allowed to do the latter. While the latter is assumed to be a Gaussian random variable, the former is not assumed to be a Gaussian random variable. In this situation, using backward reconciliation and random sampling, we propose a protocol to generate secure keys between Alice and Bob under the assumption that Eve's detector has a Gaussian noise and Eve is not so close to Alice's transmitting device. In our protocol, the security criteria are quantitatively guaranteed even with finite block-length code based on the evaluation of error of the estimation of the channel.

DOI： 10.1109/ACCESS.2022.3159331

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Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

We derive an analytical calculation formula for the channel capacity of a classical channel without any iteration while its existing algorithms require iterations and the number of iteration depends on the required precision level. Hence, our formula is its first analytical formula without any iteration. We apply the obtained formula to examples and see how the obtained formula works in these examples.

DOI： 10.1109/ISIT50566.2022.9834600

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

This paper is eligible for the Jack Keil Wolf ISIT Student Paper Award.The smooth max-relative entropy is a basic tool in quantum information theory and cryptography. In this paper, we derive the exact exponent for the decay of the small modification of the quantum state in smoothing the max-relative entropy. We then apply this result to the problem of privacy amplification against quantum side information and obtain an upper bound for the exponent of the decreasing of the insecurity, measured using either purified distance or relative entropy. Our upper bound complements the earlier lower bound established by Hayashi, and the two bounds match when the rate of randomness extraction is above a critical value. Thus, for the case of high rate, we have determined the exact security exponent. Following this, we give examples and show that in the low-rate case, neither the upper bound nor the lower bound is tight in general.Lastly, we investigate the asymptotics of equivocation and its exponent under the security measure using the sandwiched Rényi divergence of order between 1 and 2, which has not been addressed previously in the quantum setting.

DOI： 10.1109/ISIT50566.2022.9834595

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

We study commitment scheme for classical-quantum channels. To accomplish this we define various notions of commitment capacity for these channels and prove matching upper and lower bound on it in terms of the conditional entropy. Our achievability (lower bound) proof is quantum generalisation of the work of one of the authors (arXiv:2103.11548) which studied the problem of secure list decoding and its application to bit-string commitment. The techniques we use in the proof of converse (upper bound) is similar in spirit to the techniques introduced by Winter, Nascimento and Imai (Cryptography and Coding 2003) to prove upper bound on the commitment capacity of classical channels. However, generalisation of this technique to the quantum case is not so straightforward and requires some new constructions, which can be of independent interest.

DOI： 10.1109/ISIT50566.2022.9834801

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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

DOI： 10.1088/1367-2630/ac3c61

Scopus

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT45174.2021.9517803

Scopus

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

DOI： 10.1109/TIT.2021.3078812

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1751-8121/ab8b78

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Letters  

As a modern approach for the foundation of quantum theory, existing studies of general probabilistic theories gave various models of states and measurements that are quite different from quantum theory. In this Letter, to seek a more realistic situation, we investigate models approximately close to quantum theory. We define larger measurement classes that are smoothly connected with the class of POVMs via a parameter, and investigate the performance of perfect discrimination. As a result, we give a sufficient condition of perfect discrimination, which shows a significant improvement beyond the class of POVMs.

DOI： 10.1103/PhysRevLett.125.150402

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PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

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

We discuss the effect of sequential error injection on information leakage under a network code. We formulate a network code for the single transmission setting and the multiple transmission setting. Under this formulation, we show that the eavesdropper cannot increase the power of eavesdropping by sequential error injection when the operations in the network are linear operations. We demonstrated the usefulness of this reduction theorem by applying a concrete example of network.

DOI： 10.3390/e22091053

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

In this work we study the problem of secure communication over a fully quantum Gel'fand-Pinsker channel. The best known achievability rate for this channel model in the classical case was proven by Goldfeld, Cuff and Permuter, and here we generalize their result. One key feature of the results obtained in this work is that all the bounds are based on error exponents. We obtain our achievability result via the technique of simultaneous pinching. This in turn allows us to show the existence of a simultaneous decoder. Further, to obtain our encoding technique and to prove the security feature of our coding scheme we prove a bivariate classical-quantum channel resolvability lemma and a conditional classical-quantum channel resolvability lemma. As a byproduct of the achievability result obtained in this work, we also obtain an achievable rate for a fully quantum Gel'fand-Pinsker channel in the absence of Eve. The form of this achievable rate matches with its classical counterpart. The Gel'fand-Pinsker channel model had earlier only been studied for the classical-quantum case and in the case where Alice (the sender) and Bob (the receiver) have shared entanglement between them.

DOI： 10.1109/TIT.2020.3005015

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Research  

Quantum communication over network is particularly appealing in a similar way to classical network communication, but a partially corrupted quantum network has not been sufficiently studied. We discuss quantum state transmission over a partially corrupted quantum network, in which the sender transmits m0 qudits, i.e., d-level systems, to the receiver via network, but m1 channels are corrupted. As our result, we show that the optimal transmission rate is at least (m0-2m1+1)logd under the following two settings. In the first case, the unitaries on intermediate nodes are arbitrary and the corruptions on the m1 channels are individual. In the second case, the unitaries on intermediate nodes are restricted to Clifford operations and the corruptions on the m1 channels are adaptive, i.e., they are caused by an attack with a quantum memory. Further, our code in the second case realizes the noiseless communication even with the single-shot setting and is constructed dependently only on the network topology and the places of the m1 corrupted channels.

DOI： 10.1103/PhysRevResearch.2.033079

Scopus

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

Compute-and-forward (CAF) relaying is an effective way to increase bandwidth efficiency of wireless two-way relay channels. Design of error-correcting codes and their decoding algorithms suitable for CAF relaying schemes remains an important issue to be studied. In this paper, we will analyze an asymptotic behavior of LDPC codes over two-way relay channels based on density evolution (DE). Because of the asymmetric characteristics of the channel, we use the population dynamics DE combined with DE formulas for asymmetric channels to obtain the belief propagation (BP) thresholds. Additionally, we also evaluate the asymptotic performance of spatially coupled LDPC codes for two-way relay channels. The results indicate that the spatially coupled codes yield improvements in the BP threshold compared with corresponding uncoupled codes for two-way relay channels.

DOI： 10.1109/TCOMM.2020.2987891

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

Quantum private information retrieval (QPIR) is a protocol that a user retrieves one of f files from non-communicating n servers by downloading quantum systems without revealing the identity of the target file. As variants of the QPIR with stronger security requirements, the symmetric QPIR is that the files except for the target file are not leaked to the user, and the t-private QPIR is that the identity of the target file is kept secret even if at most t servers may collude to reveal the identity. The QPIR capacity is the maximum ratio of the one file size to the size of downloaded quantum systems, and we prove that the symmetric t-private QPIR capacity is min {1, 2(n - t)/n} for any 1 ≤ t < n. We construct a capacity-achieving QPIR protocol by the stabilizer formalism and prove the optimality of our protocol. The proposed capacity is greater than the classical counterpart.

DOI： 10.1109/ISIT44484.2020.9174005

Scopus

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

In the proof of Theorem 5, we stated that Eq. (47) follows from Eq. (59) of Lemma 4. However, the derivation of Eq. (59) is incorrect, and the inequality used in the derivation of Eq. (47) is not Eq. (59). Eq. (47) follows from another inequality. This correction fixes the error of our derivation of Eq. (47).

DOI： 10.1109/TIT.2020.2979957

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

We give a capacity formula for the classical communication over a noisy quantum channel, when local operations and global permutations allowed in the encoding and bipartite states preshared between the sender and the receiver. The two endpoints of this formula are the Holevo capacity (without entanglement assistance) and the entanglement assisted capacity (with unlimited entanglement assistance). What's more, we show that the capacity satisfies the strong converse property and thus the formula serves as a sharp dividing line between achievable and unachievable rates of communication. We prove that the difference between the assisted capacity and the Holevo capacity is upper bounded by the discord of formation of the preshared state. As examples, we derive analytically the classical capacity of various quantum channels of interests. Our result witnesses the power of random permutation in classical communication, whenever entanglement assistance is available.

DOI： 10.1109/ISIT44484.2020.9174125

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE International Symposium on Information Theory - Proceedings  

Differential privacy (DP) is an influential privacy measure and has been studied to protect private data. DP has been often studied in classical probability theory, but few researchers studied quantum versions of DP. In this paper, we consider classical-quantum DP mechanisms which (i) convert binary private data to quantum states and (ii) satisfy a quantum version of the DP constraint. The class of classical-quantum DP mechanisms contains classical DP mechanisms. As a main result, we show that some classical DP mechanism optimizes any information quantity satisfying the information processing inequality. Therefore, the performance of classical DP mechanisms attains that of classical-quantum DP mechanisms.

DOI： 10.1109/ISIT44484.2020.9174484

Scopus

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

CiNii Research

Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

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

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

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

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PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Letters  

DOI： 10.1103/PhysRevLett.124.120502

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PubMed

Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

DOI： 10.1109/TIT.2019.2957078

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Theory  

DOI： 10.1109/TIT.2019.2933422

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE Transactions on Information Forensics and Security  

DOI： 10.1109/TIFS.2019.2963771

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Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Letters  

DOI： 10.1103/PhysRevLett.123.260504

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review A  

DOI： 10.1103/PhysRevA.100.062335

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Review Applied  

DOI： 10.1103/PhysRevApplied.12.054047

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

DOI： 10.1088/1751-8121/ab4b64

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Scientific Reports  

DOI： 10.1038/s41598-019-49968-3

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2019.2917200

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DOI： 10.1103/PhysRevA.99.052346

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00220-019-03433-4

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIFS.2018.2868538

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1098/rspa.2019.0052

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Authorship：Lead author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ITW.2018.8613524

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ITW.2018.8613516

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Authorship：Lead author,　Last author,　Corresponding author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ITW.2018.8613305

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

DOI： 10.1088/1361-6455/aaf348

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

DOI： 10.1109/TIT.2018.2877456

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT.2018.8437491

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT.2018.8437751

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT.2018.8437744

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1109/ISIT.2018.8437783

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

DOI： 10.1088/1751-8121/aacde9

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Authorship：Last author   Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.4230/LIPIcs.TQC.2018.10

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2017.2788407

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Authorship：Last author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2017.2786669

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

DOI： 10.1103/PhysRevA.97.052308

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DOI： 10.1109/TIT.2018.2792495

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DOI： 10.1098/rspa.2017.0773

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.97.022342

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DOI： 10.1109/TIT.2017.2775612

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DOI： 10.1109/TIT.2017.2776900

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.120.030404

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.97.012302

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/2058-9565/aa8ac4

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DOI： 10.1103/PhysRevE.97.012129

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DOI： 10.1103/PhysRevA.96.062321

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DOI： 10.1088/1751-8121/aa8ffc

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DOI： 10.1103/PhysRevA.96.030301

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DOI： 10.1109/ISIT.2017.8007087

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DOI： 10.1109/ISIT.2017.8006874

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DOI： 10.1109/ISIT.2017.8006819

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DOI： 10.1109/ISIT.2017.8006713

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DOI： 10.1109/ISIT.2017.8006662

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevE.96.012128

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DOI： 10.1109/TIT.2017.2687932

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DOI： 10.1109/TIT.2017.2694012

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DOI： 10.1103/PhysRevLett.118.160502

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1214/16-AAP1216

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DOI： 10.1109/TIT.2017.2657514

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.95.032132

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DOI： 10.1109/TIT.2016.2645223

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DOI： 10.1109/TIT.2016.2636154

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DOI： 10.1007/978-3-662-49725-8_1

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Academy  

<p>Coding technology is used in several information processing tasks. In particular, when noise during transmission disturbs communications, coding technology is employed to protect the information. However, there are two types of coding technology: coding in classical information theory and coding in quantum information theory. Although the physical media used to transmit information ultimately obey quantum mechanics, we need to choose the type of coding depending on the kind of information device, classical or quantum, that is being used. In both branches of information theory, there are many elegant theoretical results under the ideal assumption that an infinitely large system is available. In a realistic situation, we need to account for finite size effects. The present paper reviews finite size effects in classical and quantum information theory with respect to various topics, including applied aspects.</p>

DOI： 10.2183/pjab.93.007

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DOI： 10.1007/978-3-662-49725-8_7

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DOI： 10.1007/978-3-662-49725-8_6

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DOI： 10.1007/978-3-662-49725-8_3

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DOI： 10.1007/978-3-662-49725-8_5

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DOI： 10.1007/978-3-662-49725-8_10

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DOI： 10.1007/978-3-662-49725-8_2

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DOI： 10.1007/978-3-662-49725-8_8

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DOI： 10.1007/978-3-662-49725-8_4

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DOI： 10.1007/978-3-662-49725-8_9

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/978-3-319-72089-0_10

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.4964755

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DOI： 10.1007/s00220-016-2738-0

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.117.090502

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1214/15-AOS1420

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2016.2567440

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DOI： 10.1109/TIT.2016.2535174

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2016.2530088

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DOI： 10.1088/1751-8113/49/16/165301

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2016.2526018

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DOI： 10.1109/TIT.2016.2530084

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.116.070403

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

There are several interesting results in quantum information theory behind the recent remarkable progress in information theory. This article focuses on the contribution of quantum information theory to information theory, and explains the role of quantum information theory in the progress in information theory, which indicates that the results of quantum information theory are applicable to other research areas.

DOI： 10.1587/essfr.10.1_4

CiNii Research

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DOI： 10.1109/TIT.2015.2495258

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2015.2492958

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.115.220502

PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.92.052308

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DOI： 10.1109/JPROC.2015.2463678

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DOI： 10.1109/TIT.2015.2464215

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00220-014-2174-y

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.70.1.0_2811

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.70.2.0_2648

CiNii Research

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DOI： 10.1109/TIT.2014.2337884

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.90.032327

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DOI： 10.1063/1.4892761

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DOI： 10.1088/1367-2630/16/6/063009

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DOI： 10.1109/ISIT.2014.6875121

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DOI： 10.1109/ISIT.2014.6875160

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DOI： 10.1109/TIT.2013.2278971

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DOI： 10.1109/TIT.2013.2276628

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.111.130407

PubMed

Publishing type：Research paper (scientific journal)   Publisher：京都大学数理解析研究所  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：京都大学数理解析研究所  

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2013.2250576

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00220-013-1678-1

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DOI： 10.1142/s0217979212430084

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CiNii Research

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DOI： 10.1088/1367-2630/14/9/093014

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

We explain second-order asymptotic theory via the information spectrum method. From a unified viewpoint based on the generality of the information spectrum method, we consider second-order asymptotic theory for use in fixed-length data compression, uniform random number generation, and channel coding. Additionally, we discuss its application to quantum cryptography, folklore in source coding, and security analysis.

DOI： 10.1587/essfr.6.12

CiNii Research

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10463-009-0254-0

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DOI： 10.1103/PhysRevA.84.012325

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2011.2110950

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DOI： 10.1007/s00220-011-1239-4

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DOI： 10.1103/PhysRevA.83.052328

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Publishing type：Research paper (scientific journal)   Publisher：国立情報学研究所  

位相推定問題についての多くの研究ではNoon 状態を入力状態として用いる方法が提案されている.理由はNoon 状態を入力状態とした場合,ある点でFisher 情報量が最大となるからである.しかし,Fisher 情報量が必ずしも達成可能な推定誤差を与えるとは限らない.本稿では,Mini-max 基準に加え,局所漸近Mini-max 基準を考え,これらの場合に,Fisher 情報量が達成可能な推定誤差を与えないことを示す.さらに,Noon 状態に代わり,漸近的に最適な入力状態を光子数に関する制約条件の下で与える.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.83.022331

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Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

In this paper, we introduce the concept of dual universality of hash functions and present its applications to various quantum and classical communication models including cryptography. We begin by establishing the one-to-one correspondence between a linear function family F and a code family C, and thereby defining ε-almost dual universal_2 hash functions, as a generalization of the conventional universal_2 hash functions. Then we give a security proof for the Bennett-Brassard 1984 protocol, where the Shor-Preskill-type argument is used, but nevertheless ε-almost dual universal_2 functions can be used for privacy amplification.

Language：English   Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

In this paper, we introduce the concept of dual universality of hash functions and present its applications to various quantum and classical communication models including cryptography. We begin by establishing the one-to-one correspondence between a linear function family F and a code family C, and thereby defining ε-almost dual universal_2 hash functions, as a generalization of the conventional universal_2 hash functions. Then we give a security proof for the Bennett-Brassard 1984 protocol, where the Shor-Preskill-type argument is used, but nevertheless ε-almost dual universal_2 functions can be used for privacy amplification.

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DOI： 10.1080/01630563.2011.557917

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DOI： 10.1080/01630563.2011.595602

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DOI： 10.2201/NiiPi.2011.8.9

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DOI： 10.1109/ISNETCOD.2011.5979076

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DOI： 10.1088/1367-2630/12/8/083002

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2010.2050805

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DOI： 10.1103/PhysRevA.81.062327

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s10463-008-0182-4

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00220-009-0909-y

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DOI： 10.1080/03610920802460761

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DOI： 10.1109/ISIT.2010.5513794

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DOI： 10.1063/1.3271041

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2009.2030478

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DOI： 10.1063/1.3234186

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1007/s00220-009-0825-1

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DOI： 10.1109/TIT.2009.2023726

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Publishing type：Research paper (scientific journal)   Publisher：一般社団法人電子情報通信学会  

We derive a new upper bound for Eve's information in secret key generation from a common random number without communication. This bound improves on Bennett's bound based on the Renyi entropy of order 2 because the bound obtained here uses the Renyi entropy of order 1+s for s∈[0,1]. This bound is applied to a wire-tap channel. Then, we derive an exponential upper bound for Eve's information. Our exponent is compared with Hayashi's exponent. For the additive case, the bound obtained here is better. The result is applied to secret key agreement by public discussion.

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1367-2630/11/4/043028

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DOI： 10.1088/1367-2630/11/4/043034

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevA.79.020303

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DOI： 10.1103/PhysRevA.79.019901

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

DOI： 10.1587/essfr.3.1_44

CiNii Research

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：The Physical Society of Japan  

DOI： 10.11316/jpsgaiyo.64.1.2.0_306_3

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1063/1.2988130

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1109/TIT.2008.928985

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Publishing type：Research paper (scientific journal)   Publisher：The Institute of Electronics, Information and Communication Engineers  

Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevLett.100.210504

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1367-2630/10/4/043029

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1088/1367-2630/10/1/013006

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DOI： 10.1103/PhysRevA.77.012104

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DOI： 10.1103/PhysRevA.76.062301

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DOI： 10.1088/1367-2630/9/8/284

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