117 citations · 207 across the 16 of their papers we have counts for
16 papers
An attainable Gill-Massar-type bound for spin-factor models
Koichi Yamagata
We determine the exact local precision limits for single-copy estimation of smooth multiparameter quantum statistical models contained in spin factors, a class of matrix Jordan alg…
Bayesian Gill-Massar Bound: An Attainable Lower Bound for Qubit Parameter Estimation
Ke-Han Zhao, Koichi Yamagata, Jun Suzuki
We study lower bounds for Bayesian quantum parameter estimation, with a particular focus on qubit models. While several lower bounds on the Bayes risk have been proposed, including…
Bayesian Monotone Metrics for Multiparameter Quantum Estimation
Jianchao Zhang, Koichi Yamagata, Jun Suzuki
Bayesian quantum estimation offers a finite-data framework for quantum sensing and metrology, yet a unified geometric formulation for multiparameter Bayes risk has been lacking. We…
Quantum Sufficiency for Self-Adjoint Statistical Models via Likelihood-Type Operators on Real -Subalgebras and Real Jordan Algebras
Koichi Yamagata
We develop a theory of quantum sufficiency on real *-subalgebras and real Jordan algebras for models consisting of general self-adjoint operators, including derivatives of states.…
Sufficient support size of measurements for quantum estimation
Koichi Yamagata
In quantum estimation for a -parameter family of density operators on a finite-dimensional Hilbert space , an estimator is specified by a pair $\left(M,\hatθ\right)…
A game-theoretic probability approach to loopholes in CHSH experiments
Takara Nomura, Koichi Yamagata, Akio Fujiwara
We study the CHSH inequality from an informational, timing-sensitive viewpoint using game-theoretic probability, which avoids assuming an underlying probability space. The locality…
Gill and Massar type bound for estimation of channel
Koichi Yamagata
In the estimation for a parametric family of quantum state on a Hilbert space , the Gill and Massar bound is known as a lower bound of weighted traces of covariances o…
Efficiency of estimators for locally asymptotically normal quantum statistical models
Akio Fujiwara, Koichi Yamagata
We herein establish an asymptotic representation theorem for locally asymptotically normal quantum statistical models. This theorem enables us to study the asymptotic efficiency of…
Maximum logarithmic derivative bound on quantum state estimation as a dual of the Holevo bound
Koichi Yamagata
In quantum estimation theory, the Holevo bound is known as a lower bound of weighed traces of covariances of unbiased estimators. The Holevo bound is defined by a solution of a min…
Quantum monotone metrics induced from trace non-increasing maps and additive noise
Koichi Yamagata
Quantum monotone metric was introduced by Petz,and it was proved that quantum monotone metrics on the set of quantum states with trace one were characterized by operator monotone f…
Noncommutative Lebesgue decomposition and contiguity with applications in quantum statistics
Akio Fujiwara, Koichi Yamagata
We herein develop a theory of contiguity in the quantum domain based upon a novel quantum analogue of the Lebesgue decomposition. The theory thus formulated is pertinent to the wea…
Noncommutative Lebesgue decomposition with application to quantum local asymptotic normality
Akio Fujiwara, Koichi Yamagata
We develop a theory of local asymptotic normality in the quantum domain based on a noncommutative extension of the Lebesgue decomposition. This formulation gives a substantial gene…
Data processing for qubit state tomography: An information geometric approach
Akio Fujiwara, Koichi Yamagata
A statistically feasible data post-processing method for the conventional qubit state tomography is studied from an information geometrical point of view. It is shown that the spac…
Experimental Demonstration of Adaptive Quantum State Estimation
Ryo Okamoto, Minako Iefuji, Satoshi Oyama +4
The first experimental demonstration of an adaptive quantum state estimation (AQSE) is reported. The strong consistency and asymptotic efficiency of AQSE have been mathematically p…
Quantum local asymptotic normality based on a new quantum likelihood ratio
Koichi Yamagata, Akio Fujiwara, Richard D. Gill
We develop a theory of local asymptotic normality in the quantum domain based on a novel quantum analogue of the log-likelihood ratio. This formulation is applicable to any quantum…
Efficiency of quantum state tomography for qubits
Koichi Yamagata
The efficiency of quantum state tomography is discussed from the point of view of quantum parameter estimation theory, in which the trace of the weighted covariance is to be minimi…