Research Of Phase Measurement Based On The Quantum-enhanced Interferometer

Precision measurement has important applications in many fields such as precise timing,information processing and high-sensitivity detection.Quantum-enhanced measurements arise as the precision of measurements is limited by the standard quantum limit（SQL）.The goal of this research field is to overcome the SQL using quantum resources such as squeezing and entanglement.In the field of precision measurement,many physical problems can be transformed into phase measurement,and the research on phase measurement has been received much attention.The advantage of the quantum interferometer is that the phase sensitivity can overcome the SQL,however,compared with the classical interferometer,the number of phasesensing particles is small,and the practical application is limited.In this paper,a new type of quantum-enhanced interferometer is proposed,whose phase sensitivity can beat SQL.And the intrinsic problem of a small number of phase-sensing particles is solved compared with a quantum interferometer.The phase measurement based on the interferometer is investigated.The details are as follows:1.A quantum-enhanced Mach-Zehnder interferometer（MZI）is proposed,which has the advantages of both MZI and SU（1,1）interferometer.Compared with the traditional MZI,besides the quantum state injection of the input port,also,a nonlinear beam splitter is used to realize the quantum-enhanced readout of the traditional MZI.Compared with the SU（1,1）interferometer that can overcome the SQL,it allows the more phase-sensing photon numbers.2.The phase estimation based on the quantum-enhanced MZI is investigated,including the linear phase estimation,the nonlinear phase estimation,and the simultaneous estimation of linear and nonlinear phase.In the linear phase estimation section,we theoretically study the quantum Cramér-Rao bound（QCRB）with the phase-averaging method.After this treatment,the term corresponding to the phase information of the input state is eliminated and a conclusive sensitivity limit can be obtained.And the phase sensitivities with the method of balanced homodyne detection and intensity detection are compared in the lossless and lossy cases.In the lossless case,the results of balanced homodyne detection and intensity detection can beat SQL and approach QCRB.In the lossy case,the result of balanced homodyne detection is better than that of intensity detection,and the effects of losses can be mitigated by optimizing the gain parameters.In the nonlinear phase estimation section,the sensitivity is improved compared to the linear phase.In the simultaneous estimation section,compared with the individual estimation,the precision of simultaneous estimation becomes worse,but it can still beat SQL,which has potential applications in the distributed quantum sensing and quantum network and so on.3.Different physical probes can be employed in the field of precision measurement,and the atom-light interferometer allows the measurement of physical quantities sensitive to both atoms and photons.In this thesis,the quantum-enhanced MZI is further broadened from the light-light system to the atom-light hybrid system,and a quantumenhanced atom-light hybrid interferometer is proposed.When atoms are illuminated by an off-resonant signal light,the AC-Stark effect will lead to phase shifts in atomic states without atomic absorption.The phase shifts are proportional to the photon number of the off-resonant signal light.By measuring the atomic phase with the quantumenhanced atom-light hybrid interferometer,we can achieve quantum non-demolition（QND）measurement of the photon number of the signal light.The condition of highquality QND measurement is obtained,and the corresponding experimental requirements and the effects of losses are analyzed.