Dynamical mean-field theory for the Hubbard-Holstein model on a quantum device

Recent developments in quantum hardware and quantum algorithms have made it possible to utilize the capabilities of current noisy intermediate-scale quantum devices for addressing problems in quantum chemistry and condensed-matter physics. Here we report a demonstration of solving the dynamical mean-field theory (DMFT) impurity problem for the Hubbard-Holstein model on the IBM Quantum Processor Kawasaki, including self-consistency of the DMFT equations. This opens up the possibility to investigate strongly correlated electron systems coupled to bosonic degrees of freedom and impurity problems with frequency-dependent interactions. The problem involves both fermionic and bosonic degrees of freedom to be encoded on the quantum device, which we solve using a recently proposed Krylov variational quantum algorithm to obtain the impurity Green's function. We find the resulting spectral function to be in good agreement with the exact result, exhibiting both correlation and plasmonic satellites and significantly surpassing the accuracy of standard Trotter-expansion approaches. Our results provide an essential building block to study electronic correlations and plasmonic excitations on future quantum computers with modern ab initio techniques.

Automated summary

Recent developments in quantum hardware and algorithms have enabled us to address problems in quantum chemistry and condensed-matter physics using current noisy intermediate-scale quantum devices. In this study, we demonstrate the solution of the dynamical mean-field theory (DMFT) impurity problem for the Hubbard-Holstein model on the IBM Quantum Processor Kawasaki. We encode both fermionic and bosonic degrees of freedom on the quantum device and use a Krylov variational quantum algorithm to obtain the impurity Green's function, achieving high accuracy.