Modified quantum Wheatstone bridge based on current circulation

Abstract We investigate a simple fermionic system designed to detect an unknown hopping rate between two sites by analyzing current circulation. The system exploits geometric asymmetry and utilizes the connection between the additional energy degeneracy point (AEDP) and current circulation for precise parameter detection. In the low-temperature, low-bias regime, with baths’ chemical potentials aligned near the degenerate energy, a balanced Wheatstone bridge condition emerges when the direction of current circulation reverses, providing a direct means to determine the unknown hopping strength. We further examine the impact of environmental interactions, demonstrating that the device remains functional under moderately strong dephasing and particle losses, though extreme environmental effects eventually degrade performance. Extending the analysis to general operating conditions, it is seen that the device continues to function effectively at higher voltages and temperatures. Finally, an analysis of the quantum Fisher information qualitatively supports our findings, revealing a sharp increase in the coherence contribution and a corresponding decrease in the population contribution near the AEDP. These results highlight geometric asymmetry as a robust and practical tool for quantum metrology.