Hermitian Operators and Unitary Operators

Shu Hotta

Shu Hotta

Rami Shakarchi

Chandana Roy

Xinzhi Zhao, Chengjie Zhang

The theoretical framework for the uncertainty relation of Hermitian operators is perfect and has been applied in many fields. At the same time, non-Hermitian operators are also widely used in some other fields. However, the uncertainty relation of non-Hermitian operators remains to be explored. K.W. Bong and his co-workers proposed the theory of unitary uncertainty relation and verified it in the experiment [Phys. Rev. Lett. 120, 230402 (2018)]. In this work, we generalized this unitary uncertainty relation theory and proposed uncertainty relations of non-Hermitian operators. Due to the difficulties in the direct measurement of non-Hermitian operators in the uncertainty relations, we simplified the uncertainty relation of two non-Hermitian operators with pure states and proposed a realizable experimental measurement scheme by using the Mach–Zehnder interferometer. When the two non-Hermitian operators are unitary, our result can reduce to Bong et al.’s result. Furthermore, for two non-Hermitian operators but not unitary, we obtained a generalized and analogous result of theirs.

Chandana Roy

Using normal operators as a common footing, the basic properties of Hermitian operators, unitary operators, and anti-Hermitian operators are treated from a unified viewpoint. The interlinks among the eigenvalues of these operators are elucidated with the help of suitable prescriptions for mapping in the plane of complex eigenvalues. Further, we show that some of the characteristics of Hermitian operators hold good under a perspective which is broader than the defining criterion for Hermitian operators.