关键词: 量子精密测量/
低频真空压缩态光场/
光纤马赫-曾德尔干涉仪/
光通信波段
English Abstract
Measurement of low-frequency signal based on quantum-enhanced fiber Mach-Zehnder interferometer
Cheng Jian1,Feng Jin-Xia1,2,
Li Yuan-Ji1,2,
Zhang Kuan-Shou1,2
1. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Shanxi University, Taiyuan 030006, China;
2. Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan 030006, China
Fund Project:Project supported by the National Key Research and Develop Program of China (Grant No. 2016YFA0301401) and the Fund for Shanxi “1331Project” Key Subjects Construction, China (Grant No. 1331KSC).Received Date:10 July 2018
Accepted Date:30 October 2018
Published Online:20 December 2019
Abstract:Generation of squeezed state at telecommunication wavelength has been recently a very interesting issue due to the lowest optical power attenuation of light at a wavelength of 1550 nm in a standard telecommunication fiber. The low-frequency vacuum squeezed state at 1550 nm in combination with fiber based interferometer offers the possibility to implement quantum precision measurement beyond standard quantum limit (SQL). In this paper, we experimentally realize a quantum-enhanced fiber Mach-Zehnder interferometer (FMZI) for measuring the low-frequency phase modulation signal by using low-frequency vacuum squeezing at 1550 nm. Firstly, the low-frequency vacuum squeezed state at the telecommunication wavelength of 1550 nm is generated by using a degenerate optical parametric oscillator (DOPO). The DOPO is a semi-monolithic construction based on a type I periodically poled KTiOPO4 (PPKTP) crystal and a concave mirror. The pump threshold of DOPO is 270 mW. When the pump power is 120 mW that is below the pump threshold of DOPO and the temperature of PPKTP is controlled at 34.8℃, a vacuum squeezing of 3 dB is generated at an analysis frequency range from 10 kHz to 500 kHz. The quadrature phase vacuum squeezing is obtained by locking the squeezed quadrature angle through using a coherent control scheme, in which two acousto-optic modulators are used to shift the frequency and produce the auxiliary beam acting as a coherent control field. Based on the constructed FMZI, a quantum-enhanced FMZI is realized by injecting the generated low-frequency vacuum squeezed state at 1550 nm into the vacuum channel of FMZI. The relative phase between two injected light fields is locked at π by using the Pound-Drever-Hall (PDH) locking technology, and the relative phase between light fields of its arms in FMZI is also locked at π/2 by using the PDH locking technology. When a phase modulation signal at the frequency of 500 kHz is loaded in the signal arm of FMZI, the noise power spectrum of the output from FMZI is measured by a balance homodyne detect system. A 2 dB quantum improvement beyond shot-noise-level at the frequency of 500 kHz is obtained experimentally by using the quantum-enhanced FMZI. The experimental results demonstrate a potential application in quantum precision measurement beyond the SQL based on fiber sensor technique.
Keywords: quantum precision measurement/
low-frequency vacuum squeezed light/
fiber Mach-Zehnder interferometer/
telecommunication wavelength
