Braverman Boris, Kawasaki Akio, Pedrozo-Peñafiel Edwin, Colombo Simone, Shu Chi, Li Zeyang, Mendez Enrique, Yamoah Megan, Salvi Leonardo, Akamatsu Daisuke, Xiao Yanhong, Vuletić Vladan
Department of Physics, MIT-Harvard Center for Ultracold Atoms and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Phys Rev Lett. 2019 Jun 7;122(22):223203. doi: 10.1103/PhysRevLett.122.223203.
Spin squeezing can improve atomic precision measurements beyond the standard quantum limit (SQL), and unitary spin squeezing is essential for improving atomic clocks. We report substantial and nearly unitary spin squeezing in ^{171}Yb, an optical lattice clock atom. The collective nuclear spin of ∼10^{3} atoms is squeezed by cavity feedback, using light detuned from the system's resonances to attain unitarity. The observed precision gain over the SQL is limited by state readout to 6.5(4) dB, while the generated states offer a gain of 12.9(6) dB, limited by the curvature of the Bloch sphere. Using a squeezed state within 30% of unitarity, we demonstrate an interferometer that improves the averaging time over the SQL by a factor of 3.7(2). In the future, the squeezing can be simply transferred onto the optical-clock transition of ^{171}Yb.
自旋压缩可以超越标准量子极限（SQL）来提高原子精密测量，而幺正自旋压缩对于改进原子钟至关重要。我们报告了在光学晶格钟原子(^{171}Yb)中实现的可观且近乎幺正的自旋压缩。利用与系统共振失谐的光通过腔反馈来压缩约(10^{3})个原子的集体核自旋，以实现幺正性。观测到的相对于标准量子极限的精度增益受态读出限制为(6.5(4))分贝，而生成的态提供了(12.9(6))分贝的增益，受布洛赫球曲率限制。使用处于幺正性(30%)以内的压缩态，我们展示了一台干涉仪，其平均时间比标准量子极限提高了(3.7(2))倍。未来，这种压缩可以简单地转移到(^{171}Yb)的光钟跃迁上。
