近日，日本理化学研究所RIKEN的S. Ulmer团队研究了反质子自旋的相干光谱学。相关论文于2025年7月23日发表在《自然》杂志上。

相干量子跃迁光谱学是计量学、量子信息处理、磁强学和标准模型精密测试的有力工具。它在质子和氘核磁矩测量方面取得了巨大的成功，并最终发展成为具有万亿分之一分辨率的微波光谱学和许多其他处于物理学前沿的实验。所有这些实验都是在宏观粒子系综上进行的，而据人们所知，“自由”单核自旋的相干光谱以前从未被报道过。

研究组展示了储存在低温潘宁阱系统中的单个反质子自旋的相干量子跃迁光谱。他们采用多阱技术，探测连续施特恩-格拉赫效应下的反质子自旋态，并将粒子传输到精密阱（PT）的均匀磁场中。他们在分析阱（AT）中推导出相干动力学并分析了量子投影测量的结果。

研究组首次观察到反质子自旋的拉比振荡，并在时间序列测量中实现了自旋相干时间约为50s时自旋反转概率大于80%的结果。单粒子自旋共振扫描显示反转大于70%，在过渡线宽度比以前的测量窄16倍，受回旋加速器频率测量退相干的限制。这一成就标志着物质/反物质对称测试的显著进步，以质子和反质子磁矩为主题的测试至少提高了10倍。

附：英文原文

Title: Coherent spectroscopy with a single antiproton spin

Author: Latacz, B. M., Erlewein, S. R., Fleck, M., Jger, J. I., Abbass, F., Arndt, B. P., Geissler, P., Imamura, T., Leonhardt, M., Micke, P., Mooser, A., Schweitzer, D., Voelksen, F., Wursten, E., Yildiz, H., Blaum, K., Devlin, J. A., Matsuda, Y., Ospelkaus, C., Quint, W., Soter, A., Walz, J., Yamazaki, Y., Smorra, C., Ulmer, S.

Issue&Volume: 2025-07-23

Abstract: Coherent quantum transition spectroscopy is a powerful tool in metrology1, quantum information processing2, magnetometry3 and precision tests of the standard model4. It was applied with great success in proton and deuteron magnetic moment measurements5, which culminated in maser spectroscopy with sub-parts-per-trillion resolution6 and many other experiments at the forefront of physics7. All of these experiments were performed on macroscopic ensembles of particles, whereas the coherent spectroscopy of a ‘free’ single nuclear spin has, to our knowledge, never been reported before. Here we demonstrate coherent quantum transition spectroscopy of the spin of a single antiproton stored in a cryogenic Penning-trap system. We apply a multi-trap technique8, detect the antiproton spin state using the continuous Stern–Gerlach effect9 and transport the particle to the homogeneous magnetic field of a precision trap (PT). Here we induce the coherent dynamics and analyse the result by quantum-projection measurements in the analysis trap (AT)10. We observe, for the first time, Rabi oscillations of an antiproton spin and achieve in time-series measurements spin-inversion probabilities greater than 80% at spin coherence times of about 50s. Scans of single-particle spin resonances show inversions greater than 70%, at transition linewidths 16 times narrower than in previous measurements8, limited by cyclotron frequency measurement decoherence. This achievement marks a notable step towards at least tenfold improved tests of matter/antimatter symmetry using proton and antiproton magnetic moments.

DOI: 10.1038/s41586-025-09323-1

Source: https://www.nature.com/articles/s41586-025-09323-1