Phase estimation via photon subtraction at the output of the hybrid interferometer

TL;DR

This paper proposes a photon subtraction-based quantum metrology scheme using a hybrid interferometer with a variable beam splitter, significantly improving phase estimation robustness against photon loss.

Contribution

It introduces a novel scheme combining photon subtraction and a variable beam splitter to enhance phase sensitivity and noise robustness in lossy quantum interferometry.

Findings

Photon subtraction improves phase sensitivity and quantum Fisher information.

Optimizing the beam splitter transmittance enhances robustness against photon loss.

Scheme surpasses the Heisenberg limit under 20% photon loss.

Abstract

The hybrid interferometer integrating an optical parametric amplifier and a beam splitter has the potential to outperform the SU(1,1) interferometer. However, photon loss remains a critical limitation for practical implementation. To address this challenge, we propose a quantum metrology scheme utilizing multi-photon subtraction at the output and replacing the conventional 50:50 beam splitter with a variable beam splitter to enhance robustness against photon loss. We employ a coherent state and a vacuum state as inputs and perform homodyne detection. Our results show that the selection of input modes significantly affects phase estimation, and optimizing the beam splitter's transmittance is crucial for maximizing phase sensitivity in lossy conditions. Furthermore, photon subtraction markedly improves phase sensitivity, quantum Fisher information, and robustness against noise. Our scheme achieves sensitivities beyond the Heisenberg limit even under 20% photon loss.