Drechsler Martín, Wolf Sebastian, Schmiegelow Christian T, Schmidt-Kaler Ferdinand
Departamento de Física, FCEyN, UBA and IFIBA, UBA CONICET, Pabellón 1, Ciudad Universitaria, 1428 Buenos Aires, Argentina.
QUANTUM, Institut für Physik, Universität Mainz, Staudingerweg 7, 55128 Mainz, Germany.
Phys Rev Lett. 2021 Oct 1;127(14):143602. doi: 10.1103/PhysRevLett.127.143602.
We demonstrate superresolution optical sensing of the size of the wave packet of a single trapped ion. Our method extends the well-known ground state depletion (GSD) technique to the coherent regime. Here, we use a hollow beam to strongly saturate a coherently driven dipole-forbidden transition around a subdiffraction limited area at its center and observe state dependent fluorescence. By spatially scanning this laser beam over a single trapped ^{40}Ca^{+} ion, we are able to measure the wave packet sizes of cooled ions. Using a depletion beam waist of 4.2(1) μm we reach a spatial resolution which allows us to determine a wave packet size of 39(9) nm for a near ground state cooled ion. This value matches an independently deduced value of 32(2) nm, calculated from resolved sideband spectroscopy measurements. Finally, we discuss the ultimate resolution limits of our adapted GSD imaging technique in view of applications to direct quantum wave packet imaging.
我们展示了对单个囚禁离子波包大小的超分辨率光学传感。我们的方法将著名的基态耗尽（GSD）技术扩展到了相干区域。在这里，我们使用空心光束在其中心的亚衍射极限区域周围强烈饱和一个相干驱动的偶极禁戒跃迁，并观察与状态相关的荧光。通过在单个囚禁的(^{40}Ca^{+})离子上对该激光束进行空间扫描，我们能够测量冷却离子的波包大小。使用4.2(1) μm的耗尽光束腰，我们达到了一种空间分辨率，这使我们能够确定处于近基态冷却的离子的波包大小为39(9) nm。该值与通过分辨边带光谱测量独立推导得出的32(2) nm的值相匹配。最后，鉴于直接量子波包成像的应用，我们讨论了我们改进的GSD成像技术的最终分辨率极限。
