叠加相干态与叠加压缩态的相位精度研究

Phase Precision of Superposition of Coherent State and Superposition of Squeezed State

利用Cramér-Rao下界法计算了叠加相干态与叠加压缩态可以达到的最优相位精度。结果表明,平均粒子数较大时,叠加相干态的精度只能达到标准量子极限,而叠加压缩态精度更高,达到了海森伯格极限。应用损耗模型,分析了二态在有损信道中传输所受到的影响。研究显示2种量子态的精度都会有所下降。最后又加入了相干态与压缩态,将4种量子状态进行比较。比较结果显示,当各态平均粒子数较大时,压缩态与叠加压缩态精度较高。当平均粒子数较小时,随着损耗的增加,叠加压缩态对外界环境的影响显得很敏感,其精度衰减得更快些。

This paper studies optimal phase precision of superposition of coherent state and superposition of squeezed state using Cramér-Rao bound approach. The results show that precision of superposition of coherent state only achieves the standard quantum limit and precision of superposition of squeezed state achieves Heisenberg limit.Using a dissipation model,we find accuracies of two quantum states decrease with increasing loss degree（η）. We also introduce coherent state and squeezed state and compare accuracies of four quantum states. When mean particle number is bigger,phase precisions of squeezed state and superposition of squeezed state are higher. When mean particle number is smaller,with the increasing loss of particle,phase precision of superposition of squeezed state decreases much faster as it is more susceptible to the environment.