利用运动压缩态实现Kasevich-Chu原子干涉仪的量子增强与多普勒抑制
Quantum enhancement and Doppler suppression of Kasevich-Chu atom interferometer with motional squeezing states
AI总结：
提出在Kasevich-Chu干涉仪中引入运动压缩态作为输入，通过最大化经典Fisher信息获得最优控制参数，实现了超越标准量子极限的灵敏度增强，并揭示了量子增强与多普勒抑制的竞争关系。
摘要：
Kasevich-Chu干涉仪中内部和外部原子自由度的杂化使得即使在量子标准极限下也能显著提高灵敏度。通过引入运动压缩态作为输入，我们系统地推导了两种测量协议在任意多普勒效应强度下的量子Fisher信息和经典Fisher信息的计算框架。通过最大化相应的经典Fisher信息，我们获得了最优控制参数和相应的量子Fisher信息。对于布居数测量，通过增大原子相干长度，最大灵敏度可达到半经典极限的四倍。对于布居数和位置的联合测量，量子增强与多普勒抑制之间的竞争导致了三种行为：在一种情况下，即使存在强多普勒展宽效应，量子增强也占主导地位，灵敏度显著提高；而在另一种情况下，观察到最优压缩参数，此时经典Fisher信息达到最大值。我们的结果清楚地证明了外部量子增强对多普勒抑制的鲁棒性。我们的方案可以很容易地应用于移动平台的重力仪，其中噪声引起的退相干会破坏内部自旋压缩的多体纠缠。
英文摘要：
Hybridization of internal and external atomic degrees of freedom in a Kasevich-Chu interferometer enables the possibility to enhance the sensitivity significantly even under quantum-standard limit. By introducing motional squeezing state as an input, we systematically derive the computational framework of quantum and classical Fisher information of two measurement protocols for arbitrary strength of Doppler effects. Through maximizing the corresponding classical Fisher information, we obtain the optimal control parameters and the corresponding quantum Fisher information. For population measurement, the largest sensitivity can be as large as four times than the semi-classical limit through enlarging the atom coherence length. For joint measurement of population and position, the competition between quantum enhancement and Doppler suppression induces two three behaviors, in one regime, the quantum enhancement dominates even in presence of strong Doppler broadening effects where the sensitivity is significantly enhanced; while in another regime, an optimal squeezing parameter is observed where the classical Fisher information reaches the maximum. Our results clearly demonstrate the robustness of external quantum enhancement against Doppler suppression. Our proposal can be readily applied to gravimeter of mobile platform where decoherence from noise will damage the many-body entanglement of internal spin squeezing.
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