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Masahito Hayashi

Publications and source records attributed to Masahito Hayashi.

314 records · Page 18Linked to original sources
arXiv2000

Subnormal operators regarded as generalized observables and compound-system-type normal extension related to su(1,1)

In this paper, subnormal operators, not necessarily bounded, are discussed as generalized observables. In order to describe not only the information about the probability distribution of the output data of their measurement but also a framework of their implementations, we introduce a new concept compound-system-type normal extension, and we derive the compound-system-type normal extension of a subnormal operator, which is defined from an irreducible unitary representation of the algebra su(1,1). The squeezed states are characterized as the eigenvectors of an operator from this viewpoint, and the squeezed states in multi-particle systems are shown to be the eigenvectors of the adjoints of these subnormal operators under a representation. The affine coherent states are discussed in the same context, as well.

quant-ph↗
arXiv1999

su(1,1) coherent states and a normal extension of su(1,1) annihilation operator: squeezed states and the simultaneous measurement of Q^{-1}P+PQ^{-1} and Q^{-2}

The the over-complete eigenvector system of the operator Q^{-1}P (Q:position, P:momentum) which consists of the squeezed states |0; s, t > with various s and t are investigated from the viewpoint of the annihilation and creation relations related to the algebra su(1,1). We derive a positive operator-valued measure(POVM) for the simultaneous measurement between the self-adjoint and anti-self-adjoint parts of PQ^{-1}.

quant-ph↗
arXiv1998

Asymptotic quantum estimation theory for the displaced thermal states family

Concerning state estimation, we will compare two cases. In one case we cannot use the quantum correlations between samples. In the other case, we can use them. In addition, under the later case, we will propose a method which simultaneously measures the complex amplitude and the expected photon number for the displaced thermal states.

quant-ph↗
arXiv1997

Asymptotic Quantum Parameter Estimation in Spin 1/2 System

For the precise estimation of the unknown quantum state, the independent samples should be prepared. Can we reduce the error of the estimation by the measurement using the quantum correlation between every sample? In this paper, this question is treated in the parameter estimation for the unknown state.

quant-ph↗