Robust Measurements of n-Point Correlation Functions of Driven-Dissipative Quantum Systems on a Digital Quantum...

Area of Science:

• Quantum Information Science
• Condensed Matter Physics
• Quantum Computing

Background:

• Measuring correlation functions is crucial for understanding complex quantum systems.
• Existing methods struggle with driven, dissipative, or open quantum systems.
• Near-term quantum computers offer new possibilities for simulating these systems.

Purpose of the Study:

• To propose and demonstrate a unified hierarchical method for measuring n-point correlation functions.
• To provide a robust technique applicable to nonequilibrium quantum systems.
• To enable accurate simulations of open quantum systems on near-term quantum hardware.

Main Methods:

• A unified hierarchical approach using an ancilla qubit.
• Controlled interaction between the ancilla and the quantum system.
• Repeated interruption of time evolution and immediate ancilla measurement.
• Comparison of robustness against interferometric techniques like the Hadamard test.

Main Results:

• Demonstration of a robust method for measuring dynamical correlation functions.
• Successful implementation on a quantum computer.
• Measurement of single-particle Green's functions for a driven-dissipative fermionic system.

Conclusions:

• The proposed method offers a robust way to measure correlation functions in driven-dissipative systems.
• This technique is advantageous for near-term quantum simulations of open quantum systems.
• Dynamical correlation functions in complex quantum systems can be reliably measured with current quantum technology.