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Local copying of orthogonal maximally entangled states and its relationship to local discrimination
Masaki Owari, Masahito Hayashi
In the quantum system, perfect copying is impossible without prior knowledge. But, perfect copying is possible, if it is known that unknown states to be copied is contained by the…
Asymptotic performance of optimal state estimation in quantum two level system
Masahito Hayashi, Keiji Matsumoto
We derived an asymptotic bound the accuracy of the estimation when we use the quantum correlation in the measuring apparatus. It is also proved that this bound can be achieved in a…
Parallel Treatment of Estimation of SU(2) and Phase Estimation
Masahito Hayashi
We discuss the accuracy of the estimation of the identical unknown actions of $\SU(2)$ by using entanglement. This problem has a similar structure with the phase estimation pro…
Finding a maximally correlated state - Simultaneous Schmidt decomposition of bipartite pure states
Tohya Hiroshima, Masahito Hayashi
We consider a bipartite mixed state of the form, $ρ=\sum_{α, β=1}^{l}a_{αβ} | ψ_α> < ψ_ β}| $, where are normalized bipartite state vectors, and matrix is posit…
Qubit Channels Which Require Four Inputs to Achieve Capacity: Implications for Additivity Conjectures
Masahito Hayashi, Hiroshi Imai, Keiji Matsumoto +2
An example is given of a qubit quantum channel which requires four inputs to maximize the Holevo capacity. The example is one of a family of channels which are related to 3-state c…