A Trade-Off Between Path Entanglement and Quantum Sensitivity

TL;DR

This paper reveals that in certain quantum measurement setups using Gaussian states, entanglement between paths can actually reduce measurement sensitivity, establishing an inverse relationship between entanglement and sensitivity.

Contribution

It demonstrates that minimizing entanglement in Gaussian states enhances phase measurement sensitivity, challenging the common notion that entanglement always improves quantum measurement precision.

Findings

Entanglement degrades measurement sensitivity in Gaussian states.

An inverse relationship exists between entanglement entropy and sensitivity.

Minimizing entanglement maximizes phase sensitivity in multimode systems.

Abstract

Entanglement often increases quantum measurement schemes' sensitivity. However, we find that in precision measurements with zero-mean Gaussian states, such as squeezed states, entanglement between different paths degrades measurement sensitivity. We prove an inverse relationship between entanglement entropy and sensitivity for measurements of single-mode phase shifts in multimode systems and for phase shifts on both modes in two-mode systems. In the two-mode case, which models devices such as interferometers, we find that entanglement strongly degrades differential phase sensitivity. Finally, we show that minimizing entanglement between paths maximizes the phase sensitivity of $N$-mode systems with zero-mean Gaussian state inputs.