Quantum metrology with quantum Wheatstone bridge composed of Bose systems

TL;DR

This paper introduces a quantum Wheatstone bridge using Bose systems for precise coupling measurement, demonstrating optimal measurement precision via homodyne detection, especially effective at low temperatures.

Contribution

It proposes a novel quantum Wheatstone bridge with Bose systems that can accurately determine unknown couplings through homodyne detection, extending classical concepts into quantum metrology.

Findings

Balanced quantum Wheatstone bridge yields optimal measurement precision.

Homodyne detection closely approaches optimal measurement at low temperatures.

Quantum Fisher information confirms measurement optimality.

Abstract

The quantum version of a special classical Wheatstone bridge built with a boundary-driven spin system has recently been proposed. We propose a quantum Wheatstone bridge consisting of Bose systems, which can simulate the general classical Wheatstone bridge. Unknown coupling can be obtained when the quantum Wheatstone bridge is balanced, which can be determined simply by the homodyne detection. When the expectation value of the homodyne detection is 0, the quantum Wheatstone bridge is unbalanced. Regulate a known coupling strength to make the expectation value of the homodyne detection be proportional to the square root of the initial number of bosons, which means that the quantum Wheatstone bridge is balanced. By calculating the quantum Fisher information, we show that the measurement precision is optimal when the quantum Wheatstone bridge is balanced. And the homodyne detection is close to the optimal measurement in the case of low-temperature baths.