Abstract

We propose and demonstrate a unified hierarchical method to measure n-point correlation functions that can be applied to driven, dissipative, or otherwise non-equilibrium systems. In this method, the time evolution of the system is repeatedly interrupted by interacting an ancillary qubit with the system through a controlled operation, and measuring the ancilla immediately afterwards. We discuss robustness of this method versus ancilla-enabled interferometric techniques (such as the Hadamard test), and implement the method on a quantum computer in order to measure single-particle Green’s functions of a driven-dissipative fermionic system. This work shows that dynamical correlation functions for driven-dissipative systems can be measured with near-term quantum computers.