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Conference on Lasers and Electro-Optics

SU(1,1) Interferometer by Direct Detection

Nan Huo, Xueshi Guo, Wen Kui Zhao, Yunxiao Zhang, Xiaoying Li, Z. Y. Ou

Published Jan 1, 2021• 0 citations
Publisher

Abstract

We report an SU(1,1) interferometer with double injection and unit gain for precision phase measurement. This scheme can increase the phase probing intensity from nW to μW to improve absolute phase measurement sensitivity.
DOI
10.1364/cleo_at.2021.jw1a.64

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SU(1,1) interferometers, based on nonlinear optical processes, potentially offer better phase sensitivity than traditional instruments. Bright-seeded variants are important for applications with large numbers of photons, yet have remained uncharacterized experimentally, for lack of a real-time technique to measure phase sensitivity. This study uses a direct intensity-detection technique to demonstrate the quantum enhancement of phase sensitivity in real time for a bright-seeded SU(1,1) system, compared to the classical shot-noise limit. It is hoped that these results will promote applications of this class of interferometer in quantum metrology.
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The sensitivity properties of an SU(1,1) interferometer made of two cascaded parametric amplifiers, as well as of an ordinary SU(2) interferometer preceded by a squeezer and followed by an anti-squeezer, are theoretically investigated.Several possible experimental configurations are considered, such as the absence or presence of a seed beam, direct or homodyne detection scheme.In all cases we formulate the optimal conditions to achieve phase super-sensitivity, meaning a sensitivity overcoming the shotnoise limit.We show that for a given gain of the first parametric amplifier, unbalancing the interferometer by increasing the gain of the second amplifier improves the interferometer properties.In particular, a broader super-sensitivity phase range and a better overall sensitivity can be achieved by gain unbalancing.
With the help of quantum entanglement, quantum dense metrology (QDM) is a technique that can make joint estimates of two conjugate quantities such as phase and amplitude modulations of an optical field, with an accuracy beating the standard quantum limit simultaneously. SU(1,1) interferometers (SUIs) can realize QDM with detection loss tolerance but is limited in absolute sensitivity. Here, we present a QDM scheme with a linear or SU(2) interferometer nested inside an SUI. By using a degenerate SUI and controlling the phase angle of the phase-sensitive amplifiers in the SUI, we can achieve the optimum quantum enhancement in the measurement precision of an arbitrary mixture of phase and amplitude modulation.