QND Measurement Based On Atom-light Hybrid Interferometer Under Lossy Conditions

Precision measurement is very important in physics research,which is mainly used to accurately measure various physical quantities.However,its measurement accuracy is limited by the standard quantum limit within the classical range.In order to improve the measurement accuracy,scientists proposed the quantum precision measurement.Most of the research on quantum precision measurement focuses on how to reduce the noise,while quantum non-demolition measurement can avoid the "back-action" noise introduced by measurement,thus breaking through the standard quantum limit.Interferometer is one of the important ways to realize quantum non-demolition measurement.In the past two years,the light-atom hybrid SU(1,1)interferometer has attracted much attention.Because the interferometer’s two interference arms are light and atoms,there is a quantum correlation between the two arms,which can break the standard quantum limit and measure a wider range.Therefore,someone propose making quantum non-demolition measurement based on the hybrid atom-light SU(1,1)interferometer,and obtain good results.However,the effect of loss on the quantum nondemolition measurement system is not considered in this work.Loss is unavoidable in the experiment,it will have a great influence on the experimental results.Therefore,in response to this situation,we do the following work:Firstly,we propose a theoretical model for quantum non-demolition measurement of the photon number in the unknown optical field with a light-atom hybrid interferometer at loss.According to the input-output relation of the interferometer under the condition of loss and combining with the criterion of quantum non-demolition measurement,we obtain the theoretical formula of the criterion of the quantum non-demolition measurement system.Secondly,we substitute the actual experimental conditions of the hot atom system and the cold atom system respectively,and mainly analyze the results of non-demolition measurement of photon quantum particles when there are various kinds of losses in the interferometer.We compare the influence of different losses on quantum nondestructive measurement and the cold atom system and the hot atom system,and find the rule of their influence on the measurement effect and explain them in principle.In addition,we also provide some parameter Suggestions for the actual experiment according to the calculated results.It provides a theoretical reference for how to select experimental conditions to improve the effect of quantum non-demolition measurement.