基于相干反馈的相敏放大器强度差压缩增强研究

Research on intensity-difference squeezing enhancement of phase-sensitive amplifier based on coherent feedback

基于原子四波混频的光参量放大器是实现强度差压缩态光场的最有效手段之一.然而,受限于原子蒸气对光场的吸收损耗,其输出的压缩度仍有待提升.光参量放大器输出的非经典光场部分反馈回输入端口,可实现其输出光场量子特性的增强.本文对相干反馈的相敏放大器开展理论分析,研究了其输出光场的强度差压缩与反馈强度、强度增益和损耗的依赖关系.研究结果表明,在无损耗的理想情况下,通过调控反馈强度和位相可实现无穷大的压缩输出.在考虑实际的实验参数条件下,此方案也可在一定的反馈强度范围内和特定的位相条件下,实现显著的压缩增强.本研究结果可为实验实现高质量非经典光场提供有益的参考.

The intensity-difference squeezed state is an important concept in quantum optics,which is not only of great significance for fundamental research in quantum physics,but also an important quantum resource in the fields of quantum communication,quantum computing,and quantum precision measurement.The optical parametric amplifier based on atomic four-wave mixing is one of the most effective means to achieve intensitydifference squeezed light.However,due to the absorption loss of atomic vapor in the light field,the output squeezing still needs improving.By feeding the non-classical optical field from the optical parametric amplifier back to the input port,the quantum characteristics of its output optical field can be enhanced.However,the intensity-difference squeezing enhancement from a phase-insensitive amplifier is experimentally realized based on coherent feedback control.The intensity-difference squeezing enhancement of the phase-sensitive amplifier has not been discussed.In this work,a two-port coherent feedback-controlled phase-sensitive amplifier is analyzed theoretically.The dependence of the intensity-difference squeezing,respectively,on the feedback intensity,the intensity gain of the optical parametric amplifier,and the losses of the system are investigated.For the ideal case in which the losses of the system are ignored,infinite squeezing can be achieved by adjusting the strength and phase of feedback.Considering the actual atomic absorption losses,squeezing enhancement can also be achieved over a wide range of intensity gains within a certain feedback intensity range.In addition,the squeezing enhancement is quite efficient for the medium intensity gain range.The intensity-difference squeezing enhancement strongly depends on the absorption loss of atomic vapor.The smaller the absorption loss,the more significant the squeezing enhancement effect is.Furthermore,the experimental feasibility of this scheme is also considered in detail.Our research can provide useful references for achieving high-quality non classical light fields in experiment,which may find applications in quantum information processing and quantum precise measurement.