title: Scheme for efficient extraction of low-frequency signal beyond the quantum limit by frequency-shift detection.
abstract: Low-frequency (Hz~kHz) squeezing is very important in many schemes of quantum precision measurement. But it is more difficult than that at megahertz-frequency because of the introduction of laser low-frequency technical noise. In this paper, we propose a scheme to obtain a low-frequency signal beyond the quantum limit from the frequency comb in a non-degenerate frequency and degenerate polarization optical parametric amplifier (NOPA) operating below threshold with type I phase matching by frequency-shift detection. Low-frequency squeezing immune to laser technical noise is obtained by a detection system with a local beam of two-frequency intense laser. Furthermore, the low-frequency squeezing can be used for phase measurement in Mach-Zehnder interferometer, and the signal-to-noise ratio (SNR) can be enhanced greatly.
authors.forename: R G
authors.initials: RG
authors.lastname: Yang
authors.forename: J
authors.initials: J
authors.lastname: Zhang
authors.forename: Z H
authors.initials: ZH
authors.lastname: Zhai
authors.forename: S Q
authors.initials: SQ
authors.lastname: Zhai
authors.forename: K
authors.initials: K
authors.lastname: Liu
authors.forename: J R
authors.initials: JR
authors.lastname: Gao