Fluctuation-dissipation relations of a tunnel junction driven by a quantum circuit

Area of Science:

• Quantum electronics
• Mesoscopic physics
• Nonlinear dynamics

Background:

• Quantum fluctuations in tunnel junctions are crucial for understanding their behavior.
• Strong quantum fluctuations in resonators can significantly alter junction dynamics.
• Classical fluctuation-dissipation relations may require modification in quantum regimes.

Purpose of the Study:

• To derive and validate fluctuation-dissipation relations for a tunnel junction driven through a resonator with strong quantum fluctuations.
• To investigate the applicability of classical fluctuation-dissipation relations in a quantum fluctuating environment.
• To demonstrate a method for reconstructing time-dependent measurements from DC bias measurements.

Main Methods:

• Derivation of fluctuation-dissipation relations incorporating quantum fluctuations.
• Modification of nonlinear current-voltage characteristics to account for circuit quantum fluctuations.
• Application of photoassisted tunneling relations for data reconstruction.
• Experimental implementation and measurement of DC current, high-frequency admittance, and current noise.

Main Results:

• Classical fluctuation-dissipation relations remain valid when quantum fluctuations are incorporated into modified nonlinear current-voltage characteristics.
• Photoassisted tunneling relations successfully reconstruct time-dependent measurements from DC bias measurements.
• Experimental measurements confirm the theoretical predictions for DC current, admittance, and noise.

Conclusions:

• The study confirms the applicability of fluctuation-dissipation relations in quantum-driven systems.
• Modified nonlinear characteristics effectively capture the impact of quantum fluctuations.
• Photoassisted tunneling provides a powerful tool for analyzing dynamic processes in quantum circuits.