ICFO-Institut de Ciencies Fotoniques, Avenida Carl Friedrich Gauss 3, 08860 Castelldefels, Barcelona, Spain.
Phys Rev Lett. 2012 Dec 21;109(25):253605. doi: 10.1103/PhysRevLett.109.253605. Epub 2012 Dec 19.
We report the generation of spin squeezing and entanglement in a magnetically sensitive atomic ensemble, and entanglement-enhanced field measurements with this system. A maximal m(f) = ± 1 Raman coherence is prepared in an ensemble of 8.5 × 10(5) laser-cooled (87)Rb atoms in the f = 1 hyperfine ground state, and the collective spin is squeezed by synthesized optical quantum nondemolition measurement. This prepares a state with large spin alignment and noise below the projection-noise level in a mixed alignment-orientation variable. 3.2 dB of noise reduction is observed and 2.0 dB of squeezing by the Wineland criterion, implying both entanglement and metrological advantage. Enhanced sensitivity is demonstrated in field measurements using alignment-to-orientation conversion.
我们报告了在磁性敏感原子系综中产生的自旋压缩和纠缠，以及利用该系统进行的纠缠增强的场测量。在一个由 8.5×10(5)个激光冷却的（87）Rb 原子组成的系综中，我们制备了最大的 m(f) = ± 1 拉曼相干性，在 f = 1 超精细基态中，集体自旋通过合成光学量子非破坏测量被压缩。这在一个混合的取向-变量中制备了一个具有大自旋排列和低于投影噪声水平的噪声的状态。我们观察到了 3.2 dB 的噪声降低和 Wineland 标准的 2.0 dB 的压缩，这意味着纠缠和计量优势。我们在使用取向到取向转换的场测量中证明了增强的灵敏度。
