31 citations · 107 across the 16 of their papers we have counts for
16 papers
Diagrammatic category theory
Kenji Nakahira
In category theory, the use of string diagrams is well known to aid in the intuitive understanding of certain concepts, particularly when dealing with adjunctions and monoidal cate…
Identifying quantum change points for Hamiltonians
Kenji Nakahira
The identification of environmental changes is crucial in many fields. The present research is aimed at investigating the optimal performance for detecting change points in a quant…
Matrix differentiation with diagrammatic notation
Kenji Nakahira
We propose a diagrammatic notation for matrix differentiation. Our new notation enables us to derive formulas for matrix differentiation more easily than the usual matrix (or index…
Generalized quantum process discrimination problems
Kenji Nakahira, Kentaro Kato
We study a broad class of quantum process discrimination problems that can handle many optimization strategies such as the Bayes, Neyman-Pearson, and unambiguous strategies, where…
Quantum process discrimination with restricted strategies
Kenji Nakahira
The discrimination of quantum processes, including quantum states, channels, and superchannels, is a fundamental topic in quantum information theory. It is often of interest to ana…
Discrimination of symmetric states in operational probabilistic theory
Kenji Nakahira
A state discrimination problem in an operational probabilistic theory (OPT) is investigated in diagrammatic terms. It is well-known that, in the case of quantum theory, if a state…
Simple upper and lower bounds on the ultimate success probability for discriminating arbitrary finite-dimensional quantum processes
Kenji Nakahira, Kentaro Kato
We consider the problem of discriminating finite-dimensional quantum processes, also called quantum supermaps, that can consist of multiple time steps. Obtaining the ultimate perfo…
Derivation of quantum theory with superselection rules
Kenji Nakahira
We reconstruct finite-dimensional quantum theory with superselection rules, which can describe hybrid quantum-classical systems, from four purely operational postulates: symmetric…
Local unambiguous discrimination of symmetric ternary states
Kenji Nakahira, Kentaro Kato, Tsuyoshi Sasaki Usuda
We investigate unambiguous discrimination between given quantum states with a sequential measurement, which is restricted to local measurements and one-way classical communication.…
Optimal discrimination of optical coherent states cannot always be realized by interfering with coherent light, photon counting, and feedback
Kenji Nakahira, Kentaro Kato, Tsuyoshi Sasaki Usuda
It is well known that a minimum error quantum measurement for arbitrary binary optical coherent states can be realized by a receiver that comprises interfering with a coherent refe…
Generalized bipartite quantum state discrimination problems with sequential measurements
Kenji Nakahira, Kentaro Kato, Tsuyoshi Sasaki Usuda
We investigate an optimization problem of finding quantum sequential measurements, which forms a wide class of state discrimination problems with the restriction that only sequenti…
Upper and Lower Bounds on Optimal Success Probability of Quantum State Discrimination with and without Inconclusive Results
Kenji Nakahira, Tsuyoshi Sasaki Usuda, Kentaro Kato
We propose upper and lower bounds on the maximum success probability for discriminating given quantum states. The proposed upper bound is obtained from a suboptimal solution to the…
Finding optimal solutions for generalized quantum state discrimination problems
Kenji Nakahira, Tsuyoshi Sasaki Usuda, Kentaro Kato
We try to find an optimal quantum measurement for generalized quantum state discrimination problems, which include the problem of finding an optimal measurement maximizing the aver…
Optimal quantum state discrimination with confidentiality
Kenji Nakahira, Tsuyoshi Sasaki Usuda, Kentaro Kato
We investigate quantum state discrimination with confidentiality. observers share a given quantum state belonging to a finite set of known states. The observers want to determi…
Optimal discrimination of quantum states on a two-dimensional Hilbert space by local operations and classical communication
Kenji Nakahira, Tsuyoshi Sasaki Usuda
We study the discrimination of multipartite quantum states by local operations and classical communication. We derive that any optimal discrimination of quantum states spanning a t…
Generalized quantum state discrimination problems
Kenji Nakahira, Kentaro Kato, Tsuyoshi Sasaki Usuda
We address a broad class of optimization problems of finding quantum measurements, which includes the problems of finding an optimal measurement in the Bayes criterion and a measur…