The Preparation And Application Of Stable Squeezed Vacuum States At 1550 Nm

With the rapid development of quantum technology,the preparation of high-quality non-classical light fields(such as squeezed states and quantum entangled states)is essential demand for applications such as quantum information and quantum metrology.The quality of the non-classical light field is directly related to the output performances of the laser source.The output performances of the output laser,including power stability,noise characteristics and so on,affect the quality of the generated non-classical light fields.The use of Mach-Zehnder Interferometer(MZI)can be used to improve the performances of the laser source,such as improvement for the power stability,and suppress the extra noise of the output laser.Subsequently the level of the squeezed states and entangled states would be improved.In the classical optical field for optical measurement,the measurement accuracy is limited by the quantum noise caused by the vacuum fluctuation of the electromagnetic field.The maximum measurement limit of a classical light source in the precise measurement process is called the standard quantum limit(shot quantum limit,SQL).Squeezed state light field can break the limitation of quantum noise on measurement and improve measurement accuracy.The noise fluctuation of one component of the squeezed light field is lower than the shot noise limit(SNL).Using the squeezed light field to measure the phase and amplitude signals beyond SQL is of great significance in the field of quantum precision measurement.The research contents of this paper are: 1.This paper first uses MZI to improve the output performance of 1550 nm output laser,and provides a high-quality laser light source for the preparation of 1550 nm non-classical light field.The working principle of MZI stabilized laser power is theoretically analyzed.The MZI is designed and constructed experimentally.The effects of the beam splitting ratio of the MZI beam splitter and the locked transmittance on the suppression of additional noise in the low frequency band of the laser are studied.When the beam splitting ratio of the optimized MZI is 90.9% and the transmittance is 85% after locking,the power stability of the 1550 nm fiber laser output laser is improved from ± 0.20% to ± 0.09%,within the analysis frequency range of 10 k Hz-35 k Hz The intensity noise of the 1550 nm laser is suppressed,especially at the analysis frequency of 15 k Hz,the intensity noise is reduced by about 8 d B.2.This paper studies the scheme and technical means of using the degenerate optical parametric oscillator(DOPO)to prepare a stable output squeezed vacuum light field.In the experiment,the cavity length of DOPO was locked by pump light,and the squeezed angle of the squeezed vacuum state at 1550 nm and the relative phase between the Local light field and the squeezed vacuum light field were locked by coherent control technology.Stable output squeezed vacuum light field at 1550 nm was obtained.Based on the experimentally prepared stable squeezed vacuum light field,orthogonal phase squeezed vacuum light field at 1550 nm was obtained by controlling the squeezed angle of the squeezed vacuum light field to fill the fiber Mach-Zehnder interferometer vacuum channel for phase signal measurement at low frequencies.The phase modulation signals were measured at 120 k Hz,140 k Hz,160 k Hz,180 k Hz,and 200 k Hz,and the phase signals were measured below SQL.The noise floor was lower than SQL by about 2.5 d B.Then,by controlling the squeezed angle of squeezed vacuum light field,orthogonal amplitude squeezed vacuum light field was obtained to achieve the measurement of the amplitude signal that breaks through SQL.The amplitude modulation signal was loaded by the amplitude modulator,and an amplitude signal measurement of about 0.5 d B lower than the SQL was obtained.The spectrum analyzer(Spectrum analyzer,SA)was used for measurement.Compared with SQL,the amplitude signal modulation sensitivity was improved by 0.5 dB.