Non-Hermitian Parent Hamiltonian from Generalized Quantum Covariance Matrix

TL;DR

This paper extends the quantum covariance matrix method to non-Hermitian systems, enabling the reconstruction of non-Hermitian Hamiltonians from biorthogonal eigenstates, with applications demonstrated in spin chains and fermion models.

Contribution

It introduces a systematic approach to determine non-Hermitian Hamiltonians from eigenstates, expanding the inverse quantum problem to non-Hermitian physics.

Findings

Successfully reconstructs non-Hermitian Hamiltonians from eigenstates.

Applies method to spin chain with Lee-Yang singularity.

Demonstrates approach on non-Hermitian interacting fermion model.

Abstract

Quantum inverse problem is defined as how to determine a local Hamiltonian from a single eigenstate? This question is valid not only in Hermitian system but also in non-Hermitian system. So far, most attempts are limited to Hermitian systems, while the possible non-Hermitian solution remains outstanding. In this work, we generalize the quantum covariance matrix method to the cases that are applicable to non-Hermitian systems, through which we are able to explicitly reconstruct the non-Hermitian parent Hamiltonian from an arbitrary pair of biorthogonal eigenstates. As concrete examples, we successfully apply our approach in spin chain with Lee-Yang singularity and a non-Hermitian interacting fermion model. Some generalization and further application of our approach are also discussed. Our work provides a systematical and efficient way to construct non-Hermitian Hamiltonian from a single pair of biorthogonal eigenstates and shed light on future exploration on non-Hermitian physics.