Dependence of measured audio-band squeezing level on local oscillator intensity noise

Abstract

We investigate the dependence of the measured squeezing level on the local oscillator (LO) intensity noise. The theoretical results indicate that it produces a large measurement error with the increase of the LO intensity noise, but the measurement error has immunity to the product P of the common mode rejection ratio (CMRR) with the LO intensity noise. According to the investigation results and the LO intensity noise, we employ a detector with the CMRR of 67 dB to detect the quantum noise at audio frequencies, the product P of the CMRR with the LO intensity noise is 20 dB below the shot noise limit (SNL), which can induce the measurement error of 0.1 dB for 10 dB of squeezing. Finally, the squeezing level measured at 15.2 kHz is 9.9 ± 0.2 dB. The influence of the intensity noise of the LO, and the electronic noise of the detector is subtracted, the inferred squeezing level is approximately 10.2 ± 0.2 dB. It is extremely important to quantify the requirements of the CMRR of the detector for measuring the squeezing at audio frequency and inferring the real squeezing level.

Generation and Measurement of Squeezed Vacuum States at Audio-Band Frequencies

“…δâ and δb are fluctuations around the mean field values of the measured field (α) and LO (β), respectively. Assuming the mean field of the measured field α is far smaller than β, the items related to the mean field of the measured field can be ignored, and the photocurrent subtraction from the two photodetectors can be written by [19]…”

“…If we define an unbalanced factor related to the CMRR of photodetectors, i.e. G = ση det2 /η det1 , the variances of the photocurrent subtraction can be written as [19]…”

“…where P com is the measured power from one photodetector when the other one is blocked, and ∆ × P com is the measured power when both photodetectors are illuminated. G can be given as [19]…”

Laser Intensity Noise Suppression for Preparing Audio-Frequency Squeezed Vacuum State of Light

“…The squeezed vacuum state of light has great significance in gravitational wave detection [2][3][4] and can be used in quantum communication, quantum storage, and precision measurement [5][6][7][8] .At the analysis frequency of MHz, the influence of laser intensity noise upon producing and detecting the squeezed vacuum state of light can be neglected as its background noise is pretty quiet and the SNL can be achieved easily [9][10][11][12][13] . The squeezed vacuum state of light at audio frequency 14 plays a vital role in certain areas of research, such as gravitational wave detection [2][3][4] , magnetic measurements [15][16][17][18][19] , and biological measurement 20 , whose sensitivity is limited by the squeezing level due to the coupling of low frequency noise. With the further exploration of audio-frequency squeezed vacuum state of light, it will open a new door for more fields.…”

A low-noise, high-SNR balanced homodyne detector for the bright squeezed state measurement in 1–100 kHz range*

“…Squeezed states are usually divided into two types: one is the bright squeezed state that has a coherent amplitude, and the other is the squeezed vacuum state that has no coherent amplitude. [1][2][3][4][5] Which type of squeezed light is desirable is dependent on the applications. In interferometer, the squeezed vacuum state is usually used to reduce the cross-interference influence due to no coherent amplitude.…”